AU614962C - An antacid composition - Google Patents

Description

AN ANTACID COMPOSITION

FIELD OF INVENTION

The present invention relates to an antacid composition with floating properties, and a method of treating or alleviating upper gastro- intestinal dyspeptic disorders.

TECHNICAL BACKGROUND

Upper abdominal dyspepsia is symptomatic of a variety of diseases such as ulcers, biliary conditions, pancreatitis and gastrooesopha- geal reflux. However, the symptoms (heartburn, regurgitation and epi- gastric pain) often associated with such conditions may also occur without apparently being attributable to any specific clinical condi¬ tions observed by X-ray or endoscopic analyses.

Thus, the symptoms are very common, at least once in a while, even among otherwise healthy individuals. It is estimated that about 50-60% of the adult population in the United States suffer from one form or another of acute upper gastrointestinal distress. The short- term or prolonged use of antacids is therefore widespread.

The antacid effect of most of the antacid compositions currently in use resides in their ability to neutralize gastric acids, resulting in an increased pH of the gastric contents. The acid neutralizing effect of such conventional antacids is known to be brief in vivo , which is ascribable to two principal causes: the normal gastric emp¬ tying rate which causes the composition to be transferred to the in¬ testines before its acid neutralizing and buffering capacities have been exhausted, and "acid rebound" or increased acid secretion in¬ duced by increased release of gastrin from the so-called G cells of the antrum which are pH sensitive, the increased production of gas¬ trin occurring at a pH of the gastric contents of about 4-5 or more. For these reasons, the acidity of the gastric contents will usually have reached its normal level 1-2 hours after ingestion of the antacid so that a dosage regimen involving the ingestion of repeated antacid dosages may be required, in particular for the long-term treatment of gastric conditions such as ulcers, rather than for short-term relief of dyspepsia.

The currently employed antacids usually contain one or more alkali metal or alkaline earth metal salts, aluminium salts or, less usual- ly, bismuth salts as acid neutralizing agents. The most commonly em¬ ployed mineral salts are sodium bicarbonate, calcium carbonate, alu¬ minium salts or magnesium salts.

Sodium bicarbonate is known as a potent, effective and rapid-acting antacid which, however, only exhibits a short-term effect. It is a systemic antacid which is not recommended for prolonged use or in large doses as systemic absorption of the sodium -ion in large quanti¬ ties may cause alkalosis which is characterized by elevated levels of carbon dioxide and an increased pH in the plasma. Symptoms of alkalo¬ sis include headache, mental confusion and anorexia.

Calcium carbonate which is a non-systemic gastric antacid is known to cause rapid, prolonged and effective neutralization of gastric acid, but is not recommended as an antacid, primarily because of its "acid rebound" effect. Studies have shown that oral administration of an isotonic calcium chloride solution results in increased gastric acid secretion both in healthy individuals and, particularly, in ulcer patients (50-75%). In another study, free calcium in the stomach has been found to release gastrin which in turn, as described above, in¬ duces the formation of gastric acid. Apart from acid rebound, it may cause hypercalcaemia and constipation.

The most commonly employed aluminium salts are the hydroxide, carbo¬ nate or phosphate, primarily the hydroxide. Its acid neutralizing capacity is lower than that of other conventional antacids, and it may cause constipation. Aluminium salts are therefore often combined with magnesium salts, such as the oxide, hydroxide, carbonate and trisilicate, which have a higher acid neutralizing capacity than the aluminium salts, but which may also cause diarrhoea. In combination preparations, the two components are balanced to offset the effect of either on gastrointestinal functions. A combination of aluminium and magnesium hydroxide gels is present in many commercial antacids. Re¬ cently, aluminium has become suspected of contributing to the deve¬ lopment of presenile dementia (Alzheimer's disease) for which reason its use as an antacid should perhaps be discouraged.

Thus, the use of the various alkaline salts discussed above is asso- ciated with several drawbacks in the form of a number of adverse effects of major or minor severity. These adverse effects are of greater importance in case of long-term treatment involving a high antacid dosage. In recent years other approaches to gastrointestinal diseases have been attempted, which have primarily been concerned with reducing acid secretion. Agents responsible for a reduction of acid secretion in the stomach comprise anticholinergics and H2-recep¬ tor antagonists. Such agents, however, suffer from the serious disad¬ vantage of having serious adverse effects in larger doses as well as being available on prescription only (which is a drawback since antacids are often used for short-term relief of dyspeptic symptoms so that reliable and safe antacid preparations should preferably be available as over-the-counter products) .

It is generally recognized that the efficacy of an antacid should be evaluated according to the following parameters: the level of acid neutralizing capacity, the period of latency before the acid neu¬ tralizing effect sets in, i.e. before the pH is increased to 3, the highest pH measured and the duration of the period during which the pH is in the range of 3-5 (it is desirable that this period should be as long as possible) . Although most of the antacids mentioned above show a high score when tested according to these parameters in vitro , their in vivo performance is less convincing due to the acid rebound and gastric emptying effects described above.

Therefore, there is a need for a safe, reliable antacid composition which exhibits the above-mentioned desirable properties of a high acid neutralizing capacity and prolonged effect without being subject to the acid rebound effect common to several of the known antacids, and which has few, if any, adverse effects. SUMMARY OF THE INVENTION

Accordingly, the present invention relates to an antacid composition which comprises

a) a substance which is soluble in water at a neutral or alkaline pH, but which is capable of forming a cohesive gel at an acid pH,

b) a substance which is capable of acting as a buffer and which is capable of being captured in the gel structure formed by sub¬ stance a) at an acid pH, and

c) one or more acid neutralizing agents capable of being trapped in the gel structure formed by substance a) at an acid pH, at least one of which causes the gel to foam when contacted with an acid,

the composition being formulated so that substance a) is dissolved before ingestion of the composition and having raft-forming proper- ties in a gastric environment.

In the present context, the term "raft-forming properties" should be understood to mean that in the gastric environment, the composition of the invention will form a highly viscous cohesive gel which floats on top of the gastric contents due to a lower bulk density than that of gastric fluid. Thus, the product of the invention will act as a barrier between the oesophagus and the gastric fluid, thereby preven¬ ting the acid gastric contents from being refluxed into the oesopha¬ gus. Another advantage of the raft-forming effect is that the acidity of the gastric fluid will not be reduced to so critical a level after ingestion of the composition as to result in a pH level at the antrum which would bring about release of gastrin from the pH sensitive G cells which in turn would induce increased acid secretion. A further advantage of the composition of the invention is that the acid neu¬ tralizing agent or agents c) are contained in the gel structure of substance a) and are therefore not emptied from the stomach at the same rapid rate observed with conventional antacid compositions where the acid neutralizing agent will be emptied from the stomach at such a rate that the acid neutralizing effect will not have been exhau¬ sted. Apart from this, the buffer incorporated in the composition of the invention will contribute to prolongating the acid neutralizing effect.

Antacid compositions which contain a gel-forming agent and an acid neutralizing agent are known (cf. N. Washington et al. , Int . J. Pharm. 27, 1985, pp. 279-286 and N. Washington et al. , Int . J. Pharm. 28 , 1986, pp. 139-143). The gel-forming agent in these known composi¬ tions is alginic acid, and they further contain sodium bicarbonate and usually at least one other acid neutralizing agent as well. When ingested, the sodium alginate forms a foaming alginate gel containing the other acid neutralizing agent or agents. This gel floats on top of the stomach contents and prevents refluxing of gastric fluid into the oesophagus. However, compositions of this type have been esti- mated to contain too low amounts of acid neutralizing agents to buf¬ fer gastric acid effectively, and contrary to the product of the pre¬ sent invention, they do not contain any buffer captured in the gel structure formed on contact with the acidic gastric fluid. In an in vitro experiment, the composition of the present invention was found to be superior to one commercial alginic acid containing antacid with respect to acid neutralizing capacity (cf. Example 5) . There is also some indication of inadequate raft formation by these known antacids (Knight et al. , J. Nucl . Med. 20 , 1979, pp. 1023-1028).

DETAILED DESCRIPTION OF THE INVENTION

Apart from forming a gel at an acid pH, substance a) should prefe¬ rably also be one which on dissolution forms a viscous mucilage, for instance when dissolved in the mouth as a result of mastication, the mucilage coating the mucous membranes of the oesophagus and stomach, thereby protecting them from the inflammatory effects of gastric acids. The mucilage formed by substance a) should preferably have a low viscosity as more highly viscous substances tend to adhere rather strongly to the teeth and produce a dryness in the mouth which would give the composition an unpleasant feel in the mouth. For the present purposes, it is advantageous to use gel-forming substances a) selec- ted from natural or synthetic polysaccharides and proteinaceous sub- stances. Suitable polysaccharides which may be employed in the compo¬ sition of the invention are selected from pectin, alginic acid, carrageenan, or a cellulose derivative such as carboxy methyl cellu¬ lose (in particular sodium carboxy methyl cellulose) .

At present, a particularly favoured polysaccharide is pectin since, apart from having favourable gel-forming and mucosa-coating proper¬ ties as defined above, it has bile acid and lipid binding properties. As bile acids are believed to influence the occurrence of gastro- oesophageal disorders (gastritis) and ulcers, pectin-containing com- positions of the invention are considered to constitute a particular¬ ly useful embodiment of the present invention. Particularly useful pectins for the present purpose are low-methoxylated pectins and ami- dated pectins. By low-methoxylated pectin is meant pectin with a de¬ gree of methoxylation of not more than 15%. Pectins with a degree of methoxylation of not more than 10%, preferably not more than 5%, are particularly preferred. Salts of such low-methoxylated pectins may also be employed such as alkaline metal salts, e.g. sodium or potas¬ sium salts.

Proteinaceous substances which may be incorporated in the composition of the invention as substance a) are advantageously selected from gelatin, milk protein such as casein or a caseinate or whey protein, an amino acid (such as glycine) or a salt thereof, or a vegetable protein such as a soy protein isolate.

The buffer substance b) which is captured in the gel structure formed by substance a) at an acid pH changes the gel characteristics in that it is dispersed in the gel structure, e.g. by agglomerating in the gel in an acid environment, i.e. on the surface of the gel. It is preferred to employ a buffer substance b) which, apart from the properties indicated above, is also capable of imparting a greater rigidity to the gel formed by substance a) at an acid pH so that it disintegrates less rapidly under gastric conditions. If, for instan¬ ce, a polysaccharide is used as the gel-forming substance a), the polysaccharide chains will enclose colloidal particles of the buffer substance b) and prevent agglomeration or coagulation thereof except on the gel surface. Without wishing to be limited to any theory, it is believed that the firmer gel structure results from enclosure of the colloidal particles of the buffer substance b) by the polysac¬ charide chains. The polysaccharide molecules are thereby pressed more closely together because of the presence of the colloidal particles taking up space which would otherwise be occupied by the polysaccha¬ ride chains (the so-called "excluded volumes" phenomenon).

Substances which have been found to exhibit excellent gel improving and buffer properties are primarily proteinaceous substances. The term "proteinaceous substances" is understood to mean substances com- prising or consisting of proteins, peptides or amino acids. Examples of suitable substances are casein or a caseinate, such as sodium, po¬ tassium or ammonium caseinate, milk powder, gelatin, a vegetable pro¬ tein such as a soy protein isolate, or an amino acid (such as gly- cine) or a salt thereof. It should, however, be understood that when the substance employed as substance a) is one of these proteinaceous substances, substance b) is not identical to substance a).

The currently most preferred buffer substances b) are casein, casei- nates and milk powder (which of course contains either or both of these) as milk proteins are known to possess a high buffering capaci- ty resulting in a longer duration of the antacid effect of the acid neutralizing agent. Furthermore, milk proteins form colloidal par¬ ticles in the gel structure of substance a) under gastric conditions, whereby the gel is broken up as explained above. Milk powder has pre¬ viously been used in itself as an antacid, but its beneficial effect in a composition of the present invention which also comprises a gel-forming agent and an acid neutralizing agent has not previously been recognized. When casein is employed as the buffer substance b) it is usually a casein acid-precipitated with, for instance, hydro¬ chloric acid or lactic acid, or rennet casein.

If the gel is sufficiently rigid in itself, it is usually not neces¬ sary to improve its properties further. In such cases, a buffer may be selected primarily for its buffering capacity. One class of advan¬ tageous buffers to be employed when gel improving properties are not specifically required are the phosphates as their buffering capacity is conveniently high at about pH 5. Examples of useful phosphates are sodium, calcium, magnesium, ammonium, aluminium or potassium phospha¬ te.

At least one of the acid neutralizing agents incorporated as substan¬ ce c) in the composition of the invention is a substance which, on reacting with acid, causes foaming of the gel formed from substance a) , due to the formation of gas bubbles by the reaction, which gas bubbles are trapped in the gel.

Substances which are capable of foaming gels when contacted with acids may be selected from some of the acid neutralizing agents used in conventional antacid compositions, e.g. pharmaceutically accep¬ table alkali metal, alkaline earth metal, aluminium, ammonium or bis¬ muth salts. The alkali metal or alkaline earth metal may be selected from sodium, potassium, magnesium and calcium. Alkaline salts exhi¬ biting the most advantageous foaming properties are the carbonate, bicarbonate or subcarbonate as these react with acid to form carbon dioxide.

An advantageous combination of acid neutralizing agents incorporated in the composition of the invention has been found to be potassium bicarbonate and magnesium subcarbonate, as the potassium bicarbonate forms carbon dioxide immediately on contact with gastric acid to foam the gel, while the magnesium subcarbonate reacts more slowly, so that the proportion of it which is not used immediately on ingestion of the composition is trapped within the foamed gel and is released slowly therefrom with formation of carbon dioxide, thereby also con- tributing to the continued floating to the gel.

The acid neutralizing agents indicated above may be combined with one or more other acid neutralizing agents, for instance oxides or hydr¬ oxides of an alkali metal or alkaline earth metal such as sodium, po¬ tassium, magnesium and calcium, or of aluminium. These will not con- tribute to the foaming of the gel, but will be trapped in the gel structure and be released slowly so that they are not emptied from the stomach before their acid neutralizing capacity is exhausted, which is a disadvantage of conventional antacids as explained above. The antacid composition of the invention may be formulated as a li¬ quid suspension of the components in a liquid which acts as a solvent for substance a) , does not cause gelling of substance a) and does not react with the acid neutralizing agent or, for that matter, with any of the other components. A typical formulation of a liquid composi¬ tion of the invention is disclosed in Example 4 below. It is, how¬ ever, preferred to formulate the composition as a chewable tablet together with conventional tabletting excipients and diluents. Such a tablet must be chewed thoroughly before being swallowed in order to obtain solution of substance a) before ingestion as it would other¬ wise not be distributed properly over the gastric contents to form the required gel. In an alternative embodiment, the composition may be formulated as an effervescent tablet together with conventional excipients. The tablet is adapted to being disintegrated in a liquid before ingestion.

The amount of each component in the composition of the invention may be varied within wide limits. Thus, substance a) may be present in an amount of 1-50% by weight per unit dose of the composition, and sub¬ stance b) may be present in an amount of 1-50% by weight. Preferably, in order to obtain a favourable balance of properties, substance a) and substance b) should be present in substantially equal amounts. The acid neutralizing agent c) may be present in an amount of 1-30% by weight per unit dose of the composition, and is preferably present in an amount of at least 5 meq of base per unit dose of the composi- tion in order to provide an adequate acid neutralization.

The composition of the present invention may be used for all the me¬ dical purposes involving the administration of antacids. Thus, the present invention further relates to a method of treating or alle¬ viating upper gastrointestinal dyspeptic disorders, comprising ad- ministering a therapeutically effective amount of the composition of the invention to a patient in need of such treatment. These disorders include gastrooesophageal reflux, gastritis, gastric or duodenal ul¬ cers, pyrosis and oesophagitis.

It has surprisingly been found that when a low-methoxylated pectin is used as substance a) , it may not be necessary to include a buffer substance b) in the composition, yet still be possible to attain a satisfactory acid neutralizing capacity. Thus, in a further aspect, the present invention relates to an antacid composition which compri¬ ses

a) a low-methoxylated pectin with a degree of methoxylation of less than about 15% or a salt thereof,

b) one or more acid neutralizing agents capable of being trapped in the gel formed by the low-methoxylated pectin at an acid pH, at least one of which causes the gel to foam when contacted with an acid, and

c) optionally a substance which is capable of acting as a buffer,

the composition being formulated so that the low-methoxylated pectin is dissolved before ingestion of the composition and having raft- forming properties in a gastric environment.

The salt of the low-methoxylated pectin is for instance an alkali metal salt, such as a sodium or potassium salt.

The low-methoxylated pectin (or pectate) employed in this composition preferably has a degree of methoxylation of less than about 10%, in particular between 0 and 5%.

This- composition may otherwise exhibit the properties and be employed for the indications mentioned above.

The invention is further illustrated by the following Examples. EXAMPLE 1

A chewable tablet according to the invention was prepared from the following ingredients

Ingredient Amount in % by weight

Pectin* 21.2

Acid casein 30.8

Potassium bicarbonate 14.2

Magnesium subcarbonate 15.7

Sorbitol 8.5

Milk powder 8.5

Peppermint oil 0.1

Aspartame 0.1

Magnesium stearate 0.5

Distilled mono- and diglycerides 0.5

100.0

* Low-methoxylated pectin with a degree of methoxylation of 0-5% (used in all Examples) .

by mixing the ingredients and compressing the mixture into tablets in a manner known per se . Each tablet contained 5 meq of base and weigh¬ ed about 1275 mg.

EXAMPLE 2

A chewable tablet according to the invention was prepared from the following ingredients Ingredient Amount in % by weight

Pectin 15.0

Casein 31.0

Potassium bicarbonate 14.2

Magnesium subcarbonate 11.6

Sorbitol 27.0

Distilled mono- and diglycerides 0.3

Magnesium stearate 0.5

10 Silicon dioxide 0.2

Flavours 0.1

Sweetener 0.1

100.0

-15—

by mixing the ingredients and compressing the mixture into tablets in a manner known per se. Each tablet contained 5 meq of base and weig¬ hed about 1275 mg.

EXAMPLE 3

20 A chewable tablet according to the invention was prepared from the following ingredients

Ingredient Amount in % by weight

Pectin 15.0

Casein 15.0 Potassium bicarbonate 7.2

Magnesium subcarbonate 18.6

Glycine 17.4

Sorbitol 10.0

Lactose 10.5 Milk powder 5.0

Mono-, di and triglycerides 0.5

Magnesium stearate 0.5

Silicon dioxide 0.2

Sweetener 0.1 Flavours 0.1

100.0

by mixing the ingredients and compressing the mixture into tablets in a manner known per se . Each tablet weighed about 1275 rag.

EXAMPLE 4

A liquid composition of the invention was prepared from the following ingredients

Ingredient Amount

Pectin 380 mg

Casein 380 mg

Magnesium subcarbonate 474 mg

Potassium bicarbonate 184 mg

Flavours q.s.

Sweetener q.s.

Water 25 g by mixing the ingredients in a manner known per se . This mixture may be filled into a suitable container before use.

EXAMPLE 5

Compositions according to the invention (according to Example 1) were tested in vitro in simulated gastric fluid in accordance with the following method:

100 ml of a mixture of simulated gastric fluid (USP XX) and distilled water (4:6), pH about 1.3, were placed on a magnetic stirrer (FRAMO M22/1) operated at 500 rpm. When the pH had stabilized (about 1.25), the antacid sample to be tested was added.

One minute after the addition of the sample, a continuous addition of simulated gastric fluid, pH 1.2, (at a rate of about 2 ml/min. corre¬ sponding to about 10 mmoles/hour) was carried out by means of an IS- MATEC mini-S 840 pump provided with an ENE 09-tube. The pH was deter- mined by means of a PHM 84 pH meter (Radiometer, Denmark) connected to a BBC, SE 120 recorder.

The composition of the invention was tested with respect to the fol¬ lowing parameters: The duration of the latency period before a pH of > 3 is obtained (this pH was set as the pH at which the antacid ef- feet occurs) , the highest pH recorded, variations in the pH range of 3-5, and the duration of the period of time before the reaction mix¬ ture reaches a pH of 2, at which pH the experiment is stopped. The composition of the invention was compared with two conventional antacids with respect to these parameters: 1) potassium bicarbonate and magnesium carbonate, and 2) Gaviscon® (a combination of alginic acid, sodium bicarbonate and aluminium hydroxide, produced by Fer- ring, Sweden) . The results appear from Table 1. TABLE 1

Latency period Maximum Duration Duration of pH 3 pH of pH = period before

(seconds) 3-5 pH = 2 is (minutes) reached (minutes)

Mixture of 340 mg of potassium bi- carbonate and 277 mg of magnesium carbonate 70 3.74 6.5 21

Composition of the invention 24 4.88 30.5 55

Gaviscon®, 3000 mg 1.56 .1) .1)

1) As the pH did not reach 3, the duration of the antacid effect could not be recorded.

It appears from the Table that the highest pH (4.88) was recorded for the composition of the present invention. The buffer capacity was also most pronounced for the composition of the invention, pH values of more 2 being recorded for 55 minutes. On the basis of these re¬ sults, it is concluded that compared with a mixture of alkaline salts and Gaviscon®, respectively, the product of the invention was found to show the highest acid neutralizing buffer capacity when determined by means of this in vitro method.

EXAMPLE 6

Compositions of the invention were further tested for the effect of incorporating varying amounts of the active ingredients a) , b) and c) with respect to the maximum pH obtained and the duration of the acid neutralizing effect. The method used to test these parameters/vari¬ ables was similar to that described in Example 5, namely the in vitro method using simulated gastric fluid.

The effect of casein on the maximum pH and duration of the acid neu- tralizing effect appears from Table 2 below. 184 mg of KHCO3 + 480 mg of MgC03 were used as the base, corresponding to 10 meq of base.

TABLE 2

10 meq 10 meq 10 meq of base + 397 mg of + 794 mg of (without casein) casein casein

Maximum pH 5.8 5.2 5.05

Duration of effect to pH 2.5 54 min. 56 min. 60 min.

The effect of pectin on the maximum pH and duration of the antacid effect appears from Table 3 below.

TABLE 3

Amount of base 5 meq 92 mg of KHCO3 no pectin added + 546 mg of pectin 240 mg of MgC0₃

Maximum pH 2.0 Duration of effect to pH 2.5 16 min.

The effect of the ratio between casein and pectin on the maximum pH, duration of the antacid effect and foaming appears from Table 4 be¬ low. The same amount of base, 10 meq (343 mg of KHCO3 + 283 mg of gCU3) , was used in each experiment. TABLE 4

Experiment No. 10

Pectin 238 mg 378 mg 630 mg 382 mg

Casein 1000 mg 800 mg 900 mg 382 mg

Maximum pH 4.5 4.9 3.5 5.7

Foaming 20 ml 45 ml 55 ml 35 ml

Duration of effect to pH 2.5 37.5 min. 36.5 min. 24 min. 70 min.

It appears from Tables 2-4 that the amount of casein incorporated in the composition affects the duration of the acid neutralizing effect expressed as the time period before a pH of 2.5 is obtained so that a larger amount of casein incorporated leads to a longer duration of the effect, while on the contrary, a larger amount of pectin incorpo¬ rated leads to a lower maximum pH and a shorter duration of the acid neutralizing effect. However, the amount of pectin also affects the degree of foaming obtained, so that, when formulating the composition of the invention, a balance must be reached between the amount of casein and the amount of pectin incorporated in the composition.

EXAMPLE 7

A chewable tablet according to the invention was prepared from the following ingredients:

Alginate

Casein 15.0

Alginic acid *) 15.0

Potassium bicarbonate 7.2

Magnesium carbonate 18.6

Glycine 6.35

Whey powder 15 5.0

Xylitol 30.0

Mono-, di-, triglycerides 0.5

Magnesium s ear te 0.5

Silicon dioxide 0.2

Saccharine 0.15

Citric acid 1.0

Aroma 0.5

100.0

*) Purchased from Grindsted Products, Denmark (VLVA Sample I; Catalogue No. 2001814)

by mixing the ingredients and compressing the mixture into tablets in a manner known per se . Each tablet weighed about 1275 mg.

This composition was tested as described in Examples 5 and 6 and compared with the composition according to Example 3. The results appear from Table 5 below.

TABLE 5

Alginic acid Pectin

Maximum pH 5.2 5.7 Duration of period before pH - 2.0 is reached (minutes) 84 106 Foaming 1 tablet 6 ml 25 ml 30 min. 2 tablets 12 ml 32 ml

It appears from Table 5 that alginic acid produces less foaming of the gel than pectin.

EXAMPLE 8

Chewable tablets according to the invention were prepared from the following ingredients:

Protein Calcium No casein Acid caseinate casein

Pectin 14.8 14.8 14.8 14.8

Calcium caseinate - 30.8 - -

Acid - - - 30.8

Soy protein 30.8 - - -

Potassium bicarbonate 7.2 7.2 7.2 7.2

Magnesium carbonate 18.6 18.6 18.6 18.6

Tabletting exci¬ pients, flavours and sweeteners 28.6 28.6 28.6 28.6

1 tablet 1200 mg 1200 mg 830 mg 1200 mg

Foaming 24 ml 10 ml 20 ml 24 ml

by mixing the ingredients and compressing the mixture into tablets in a manner known per se.

The compositions were tested substantially as described in Examples 5 and 6 for the degree of foaming obtained. The results are shown above. It appears from the table that soy protein compares favourably with acid casein with respect to foaming.

EXAMPLE 9

Clinical testing of the composition of the invention

The composition of Example 1 was tested for its therapeutic effect, possible adverse effects and acceptability in comparison with conven¬ tional antacids (Balancid® [composed of aluminium hydroxide and mag¬ nesium carbonate], Novaluzid® [composed of aluminium hydroxide, mag¬ nesium hydroxide and magnesium carbonate] , Link® [composed of alumi- nium hydroxide and magnesium carbonate] and Titralac [composed of calcium carbonate] .

The study was carried out at the out-patients clinic of the medical department of gastro-enterology, Ulleval Hospital, Oslo, Norway, from February to May 1986. 20 patients (12 male and 8 female patients be¬ tween 23 and 64 years of age) who suffered from upper abdominal dys¬ peptic symptoms and whose informed consent had been obtained, were included in the study. The average age was 40 years. 15 of the pa¬ tients used Balancid® at the time they were included in the study. Patients were excluded from the study if they suffered from a gastro- scopically verified peptic ulcer, erosive prepyloric changes, severe gastritis or other organic gastrointestinal diseases that might ex¬ plain the presence of symptoms, or if they used drugs known to affect the gastrointestinal tract. Thus, all the patients included in the study were diagnozed to suffer from non-ulcer dyspepsia (NUD) .

The patients visited the clinic twice, at the beginning of the test treatment and after two weeks of treatment. Three of the patients did — not show up at the second consultation which left therapeutic results from 17 patients available. During the test period, the patients - daily filled in a dosage form and registered the side effects and adverse reactions experienced. During the two-week period, the com¬ position of Example 1 was taken according to need; however, no more than two tablets were taken at a time. 13 of the patients took the composition of the present invention for the entire period with an average intake of 52 tablets (within a range of 19-100). Four of the patients prematurely stopped taking the composition of the invention: patient No. 3 after 7 days because he had to take Balancid® as before and therefore saw no reason to continue the treatment with the com¬ position of the invention; patient No. 5 after 8 days because he was free of symptoms; No. 11 because the ingestion of two dosages on the first day lead to nausea and vomiting; and No. 18 after 9 days due to hospitalization with severe vomiting and dehydration (diagnozed as severe gastritis - not ascribable to the ingestion of the composition of the invention) . A final overall evaluation of the composition of the invention was obtained from 17 patients; 11 of the patients were satisfied with the test treatment, 3 considered it to be equal to previous treatment while 3 were dissatisfied (two of the patients due to an insufficient effect and one due to nausea/vomiting) . The effect of the composition of the invention is shown in Table 6 with respect to various symptoms registered according to severity and duration.

The results were analyzed statistically using a Student's T-test, p-0.05. Variables with presumed continuous distribution were analyzed using non-parametric tests. For variables with non-continuous distri¬ bution, categoric data analysis was used.

TABLE 6

Symptoms Improved Unchanged Aggravated

Regurgitation 10 6 0 p<0.01

Heartburn 7 6 3 p=0.14

Epigastric pain 13 2 1 p<0.01

Abdominal pain 5 10 1 p=0.11

Nausea 10 6 0 p<0.01

Vomiting 4 12 0 p=0.13

The results show that regurgitation, epigastric pain and nausea -were significantly reduced (p<0.01) during the two-week test period while heartburn, abdominal pain and vomiting improved, but were not statis- tically significant. Periods of latency and the duration of the ef¬ fect appear from Tables 7 and 8. TABLE 7

Period of latency (minutes) Previous Composition of Difference treatment the invention

No. of patients 12 13 10

Mean 21.6 18.8 -5.9

Median 17.5 15 -3.5

Range 0.5-60 1-60 (-40)-50 p-0.24

TABLE 8

Duration of effect (hours) Previous Composition of Difference treatment the invention

No. ^•of patients 11 13 9

Mean 5.3 7.1 0.8

Median 3.5 5 2.5

Range 1-24 1-24 (^• -23)-17 p=0.10

It appears from the Tables that the recordings varied considerably, but the profile of the duration tended to be increased with the com¬ position of the invention than with the conventional antacids used as controls.

It appears from these results that the effect of the composition com¬ pares favourably with previous antacid treatment. EXAMPLE 10

Clinical testing of the composition of the invention

The composition of Example 3 was radiolabelled with indium-113m and the gastric distribution and residence time of the composition was then measured in six healthy subjects using the technique of gamma scintigraphy, and the effect of the formulation on the gastric empty¬ ing of a test meal was measured.

Four healthy male and 2 healthy female subjects, age range 18-25 years, participated in the trial. Exclusion criteria included weight outside the range of ± 10% group mean weight, consumption of medica¬ tions which could influence the results of the study, a history of gastrointestinal disorders, excessive tobacco or alcohol consumption or participation in a similar study within the previous 12 months. Female subjects who had not menstruated within the previous 28 days were also excluded. Written informed consent was obtained from the subjects prior to entry into the trial.

The subjects were fasted overnight and on the morning of the study given a radiolabelled scrambled egg breakfast composed of

2 eggs (60 g) radiolabelled with 1 MBq technetlum-99m sulphur colloid added to the egg prior to cooking, 30 ml of milk, 25 g of butter, 2 slices of toast, 200 ml of unsweetened orange juice.

Total calorific value 1693 kJ.

The scrambled eggs were labelled by addition of technetium-99m sul¬ phur colloid to the ingredients before cooking.

Thirty minutes later, the subjects were given two radiolabelled crushed tablet in 20 ml of water or a placebo. The tablets had been radiolabelled by adding 3 MBq indium-113m in 1 ml of 0.04 M hydro- chloric acid to 2 crushed tablets of the composition of Example 3, and this was stirred until a uniform paste was formed. This was added to 125 ml of simulated gastric juice (USP formulation) at 37°C. The mixture was stirred to form a suspension in the acid. 2 ml samples of the mixture were removed at intervals and centrifuged at 2500 rpm. The pellet was washed by resuspending it in distilled water and by recentrifugation. Samples of the pectin, washings and supernatant were counted to assess the tenacity of the radiolabel for the pectin.

A cross-over study was performed, separated by a one week interval. Anatomical reference markers were made by drying small quantities of technetium-99m onto 0.5 x 0.5 cm² pieces of filter paper and covering with waterproof tape. The markers were taped on the subjects' skin anteriorly and posteriorly, opposite the stomach, to act as a refe¬ rence point for alignment of images.

Anterior and posterior images of 30 seconds' duration were recorded at 15 minutes' intervals until the stomach was empty (approximately 5 hours). The technetium and indium images were recorded simultaneously but stored separately in the computer for subsequent analysis.

Each image was analyzed by creating three regions of interest, one around the whole stomach, the second around the top half of the sto¬ mach and the third to assess background activity. The count rates from the regions of interest were corrected for background and decay. The technetium count rates were also corrected for the overlap of the indium energy into the technetium channel. The geometric mean of the activity in the regions of interest in the anterior and posterior images were calculated to correct for attenuation.

More than 86% of the indium-113m was found to be associated with the pectin phase after two hours of incubation with simulated gastric juice at 37°C in vitro . This established the suitability of the label to enable the behaviour of this formulation to be followed by gamma scintigraphy.

The composition of the invention emptied significantly later than the test meal and more than 50% of the dose remained in the fundus for 3 hours. The time for half the formulation and food to leave the sto¬ mach (T50) for each subject is shown in Table 9 and the mean T5QS ± sd are 4.13 ± 0.69 hours and 2.17 ± 0.15 hours, respectively. The composition of the invention was not found to have a significant effect on the gastric emptying of the test meal, with 50S of 2.17 ± 0.15 hours and 1.7 ± 0.32 hours for drug and placebo, respectively.

TABLE 9

Time (hours) taken to half empty stomach

Subject Composition Food + composition Food + placebo

1 4.4 2.2 1.4

2 4.1 2.1 1.4

3 4.36 2.3 1.6

4 4.6 2.25 2.3

5 4.25 2.25 2.0

6 2.8 1.9 1.7

Mean ± s . d. 4. .13 + 0. .69 2. .17 + 0. .15 1. .7 ± 0.32

EXAMPLE 11

An effervescent tablet according to the invention was prepared from the following ingredients:

Citric acid 800 mg

Potassium bicarbonate 500 mg

Sodium bicarbonate 500 mg

Magnesium carbonate 480 mg Pectin 380 mg

Casein 380 mg Tabletting excipients, flavour, colour and sweetener 960 mg

4000 mg

The amount of foaming after 30 minutes was 35 ml when the composition was tested as described in Examples 5 and 6.

REFERENCES

1. H.A. May, C.G. Wilson, J.G. Hardy, Int. J. Pharm. 19 , 1984, 169- 176.

2. N. Washington, C. Washington, C.G. Wilson, Int . J. Pharm. 1987, in press.

3. B. Flourie, N. Vidon, J.A. Chayvialle et al., Am. J. Clin . Nutr. 42, 1985, 495-503.

4. M. Feldman, H.J. Smith, T.R. Simon, Gastroenterology 87, 1984, 895-902.

5. L.S. Malmud, N.D. Charkes, J. Littlefield et al., J. Nucl . Med . 20 , 1979, 1023-1028. 6. L.S. Knight, A.H. Maurer, L.A. Anmar et al. , J. Nucl . Med. 27, 1986, 1011-1012.

7. B. Flourie, N. Vidon, C. Florent, J.J. Bernier, Gut 25 , 1984, 936-941.

8. S. Holt, R.C. Heading, D.C. Carter et al., Lancet i , 1981, 636- 639.

9. A.R. Leeds, D.N. Ralphs, F. Ebied et al. , Lancet i , 1981, 1075- 1078.

10. D.N. Ralphs, 0. Lawaetz, N.J.G. Brown, Gut 19 , 1978, 986-7A abstract.

Claims (26)

1. An antacid composition which comprises

a) a substance which is soluble in water at a neutral or alkaline pH, but which is capable of forming a cohesive gel at an acid pH,

b) a substance which is capable of acting as a buffer and which is capable of being captured in the gel structure formed by substance a) at an acid pH, and

c) one or more acid neutralising agents capable of being trapped in the gel structure formed by substance a) at an acid pH, at least one of which causes the gel to foam when contacted with an acid,

the composition being formulated so that substance a) is dissolved before ingestion of the composition and having raft-forming proper¬ ties in a gastric environment.

2. A composition according to claim 1, in which the substance defined under a) in claim 1 is selected from natural or synthetic polysaccha- rides and proteinaceous substances.

3. A composition according to claim 2, in which the polysaccharide is selected from pectin, dextran, alginic acid, carrageenan, and a cel¬ lulose derivative such as carboxy methyl cellulose.

4. A composition according to claim 2, in which the proteinaceous substance is gelatin, milk protein such as casein or a caseinate, or whey protein, an amino acid (such as glycine) or a salt thereof, or a vegetable protein such as a soy protein isolate.

5. A composition according to claim 1, in which the substance defined under b) in claim 1 is further capable of imparting a greater rigidi¬ ty to the gel formed by substance a) at an acid pH.

6. A composition according to claim 5, in which the substance is a proteinaceous substance.

7. A composition according to claim 1, in which the substance defined under b) in claim 1 is a phosphate.

8. A composition according to claim 7, in which the phosphate is se¬ lected from sodium, calcium, magnesium, ammonium, aluminium and po- tassium phosphate.

9. A composition according to claim 6, in which the substance is casein or a caseinate, such as sodium, potassium or ammonium casei¬ nate, milk powder, gelatin, a vegetable protein such as a soy protein isolate or an amino acid (such as glycine) or a salt thereof with the proviso that when substance a) is one of these substances, substance b) is not the same substance as substance a) .

10. A composition according to claim 1, in which the acid neutraliz¬ ing agent defined under c) in claim 1 is a substance which, on react¬ ing with acid, causes foaming of substance a) .

11. A composition according to claim 10, in which the substance is selected from a pharmaceutically acceptable alkali metal or alkaline earth metal salt, aluminium salt, ammonium salt or bismuth salt.

12. A composition according to claim 11, in which the alkali metal or alkaline earth metal is selected from sodium, potassium, magnesium and calcium.

13. A composition according to claim 11, in which the salt is a car¬ bonate, bicarbonate or subcarbonate, or a combination thereof with an oxide or hydroxide of an alkaline metal or alkaline earth metal such as sodium, potassium, magnesium or calcium, or of aluminium.

14. A composition according to claim 11, in which the ammonium salt is selected from ammonium carbonate or ammonium bicarbonate.

15. A composition according to claim 11, in which the bismuth salt is bismuth carbonate.

16. A composition according to claim 1, which is In the form of a chewable tablet.

17. A composition according to claim 1, in which substance a) Is present in an amount of 1-50% by weight per unit dose of the compo- sition.

18. A composition according to claim 1, in which substance b) is present in an amount of 1-50% by weight per unit dose of the compo¬ sition.

19. A composition according to claim 1, in which substance a) and substance b) are present in substantially equal amounts.

20. A composition according to claim 1, in which the acid neutra¬ lizing agent c) is present in an amount of 1-30% by weight per unit dose of the composition.

21. A composition according to claim 20, in which the acid neutrali- zing agent c) is present in an amount of at least 5 meq of base per unit dose of the composition.

22. A method of treating or alleviating upper gastrointestinal dys¬ peptic disorders, comprising administering a therapeutically effec¬ tive amount of a composition according to claim 1 to a patient in need of such treatment.

23. A method according to claim 22, in which the dyspeptic disorder is selected from gastroesophageal reflux, gastritis, gastric or duo¬ denal ulcers, pyrosis and oesophagitis.

24. An antacid composition which comprises

a) a low-methoxylated pectin with a degree of methoxylation of less than about 15% or a salt thereof,

b) one or more acid neutralizing agents capable of being trapped in the gel structure formed by the low-methoxylated pectin at an acid pH, at least one of which causes the gel to foam when contacted with an acid, and

c) optionally a substance which is capable of acting as a buffer,

the composition being formulated so that the low-methoxylated pectin is dissolved before ingestion of the composition and having raft- forming properties in a gastric environment.

25. A composition according to claim 24, wherein the salt of the low- methoxylated pectin is an alkali metal salt such as a sodium or potassium salt.

26. A composition according to claim 24, wherein the low-methoxylated pectin or salt thereof has a degree of methoxylation of less than about 10%, in particular between 0 and 5%.