CA1062614A

CA1062614A - Oleophilic clay pharmaceutical formulations

Info

Publication number: CA1062614A
Application number: CA235,109A
Authority: CA
Inventors: Christopher D. Clarke
Original assignee: Beecham Group PLC
Current assignee: Beecham Group PLC
Priority date: 1974-09-21
Filing date: 1975-09-09
Publication date: 1979-09-18
Also published as: SE426909B; IE41461B1; JPS5745413B2; NL7511059A; DK421075A; NZ178490A; FR2285146A1; AU8506875A; SE7510365L; DK143887B; JPS5161619A; BE833432A; DK143887C; DE2541881C2; NL185060C; FR2285146B1; ZA755515B; IE41461L; GB1512378A; NL185060B

Abstract

ABSTRACT OF THE DISCLOSURE
A fluid pharmaceutical formulation for oral administration to animals comprising a medicament, and edible oil and an oleophilic clay.
The oleophilic clay thickening agent is formed by replacement of inorganic cations in a natural or synthetic clay by organic cations.

Description

lQ6Z614 This inveati~n relates to pharmaceutical formulations znd in particular to oil-based formulations for oral adminis-tration of medicarnents to domestic animals.
For the administration of insoluble medicaments to animals by the oral route, the medicament is often presented as a suspension. In preparing such a suspension, it is generally desirable t}-~at the formulation base .is of such a ViSGosity that the suspended material does not readily sediment out.
For reasons of stability, ready-to-use antibiotic suspensions are customarily prepared in an oily base. In order to produce an oily base whi~h is sufficiently gel-like, the oil is heated in the presence o~ a suitable thickening agent, typically alwninium stearate. Such a process is lengthy and involved and therefore expensive. In addition, the rheological characteris-tics of the final gel are markedly influenced by slight varia-tions in the time/temper~ture conditions obtained during manufacture.
~t is therefore an object of the present invention to provide an oil-based for~ul~tion which is simple and economical ~o

2~ prepare commercially, shows minimum batch tc batch variation, and is sufficiently gel-like to be suitable as a base for th~
incorporation of medicame~s, and their oral administration to animals.
Accordingly, the present invention provides a fluid pharma-ceutical formulation for oral administratior. to animals which formulation comprlses a medicament, an edible oil and an oleophilic clay.

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By the term oleophilic cl~y used herein is meant a natural or synthetic clay which has been rendered more easily dispersible in edible oil by replacement of inorganic cations therein by organic cations.
5uitable organic cations include ammonium ions substituted by at least one C12 18 alkyl group. Examples of such cations include cations of the formula (I):
Rl / (I) where Rl is a C12 18 alkyl group, R2 is either a second C12 18 alkyl group, a benzyl group, a Cl 6 alkyl group or hydrogen, and R3 and R4 are each a Cl 6 alkyl group or hydrogen. Examples of suitable cati~ns within formula (I) include octadecyl ammonium, dimethyl mono- and di-octadecyl ammonium, dimethyl hexadecyl ammonium, and dimethyl benzyl octadecyl ammonium ions. Preferably in formula (I) Rl is a Cls 18 lkyl group~ R2 is a C15_18 alkyl group or a benzyl, methyl or ethyl group ~r hydrogen, and R3 and R4 are each a methyl or ethyl group or hydrogen.
Suitable clays for this ion-exchange threatment and subsequent use in the invention are usually those characterised by a high cation exchange capacity and high surface area.
~xamples of oleophilic clays include those clays sold commer-cial;y as Bentones*(modified Bentonite, Berk Ltd.) and Attagels*(modified Attapulgite, Engelhard). The Bentones are * Trade Mark :,- - 3 - , : , . . - :, - :.. : . . . , : .
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~06Z614 mo~tmorillon t~s in which inorganic cations have been replaced by alkyl ammonium cations as described above, normally octadecyl ammonium, dimethyl mono- or di-octadecyl ammonium, dimethyl hexa-decyl or dimethyl benzyl octadecyl am;nonium ions, or similarly substituted hectorites. The A~tagels are similarly substituted hydrated magnesi~ aluminium silicates belonging to the mont~
morillonite group of clays, but having a higher magnesium content than nor~nal montmorillonites and containing traces of calcium and iron.
Oleophilic clays have been reported as additives for oin-t-ment bases (Bill~ps and Seger, Am. J. Pharm., 1964, ~ , 183-205) but such topical formulations are not of course sufficiently fluid for oral administration forms and there is no suggestion in that publication of fluid oil-based formulations containing the modified c~ ys, or of their advantageous properties.
The edible oil employed in the formulations of this invention should not be liable to substantial drying or oxidation.
Preferably a vegetable oil is employed and suitable examples include sunflower oil, arachis oil, soya-bean oil, rapeseed oil, and maize oil.
The present formulations are oI value for any type of medi~
cament and are particularly useful for orally administrable anti-biotics, such as ampicillin, amoxycillin, cloxacillin, fluclo-xacillin1 and the 5-indanyl and phenyl esters of carbenicillin, and other antibiotics useful in the treatment of gut infections.
Such medicame~ts usually represent 1 to 15% of the formulation, suitably 3 to 10~6 of the formulation.

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A polar solvent m~y also ~e advantageously incorporated into the folmulations in or~er to încrease the ease with which the oleophilic clays may be fully dispersed in the edible oil during the preparation of the formulation. It is necessary th~t the solvent be compatible with the medicament, non-toxic, substantially more polar than the edible oil and miscible with the edible oil. For penicillins, a suitable polar sol~ent is propylene carbonate. The polar solvent may constitute from O
to 2% of the total formulation and in general the polar solvent will be present in the formulation in a w~ight that is O to 40%
of the weight of oleophilic clay.
The amount of oleophilic clay present in the formulation to produce the desired properties will normally be in the range of 0.1 to 25%. Obviously lower percentage incl~sions will be preferred when a polar solvent is present, higher percentage inc.lusions preferred in the absence of a polar solvent. In general however 1 to 5% of oleophilic clay will normally be rnost s~tisfactory, preferably in the presence of 0..1 to 2.0% of polar solvent.
When the formulation is to be used for the treatment of an animal diarrhoea or scours, it may also be of advantage to include in the formulation a natural or synthetic clay absorbent.
The amount of such clay present may be from 1 to 20%, preferab7y `
5 to 15%, and examples of such clays include Bentonite and Attapulgite.
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The e~ible oil will represellt the balance of the for~ula-- tion, ~nd will norl.lally be present as at least, 50%, suit~bly as at l~as-t 75%, of the formulation.
From the fore~oirlg, it can be seen that a prefered embodi-ment of this invention is a pharmaceutical formulation as defined above which co;nprises ~ to 15~ medicament, 1 to 55' oleophilic clay, 0.1 to 2.09~ polar solvent, and edi~le oil to 1007~. Into this preferred fo~ulation may suitably be incorporated 5 to 15,b of natural or synthetic clay absorbent.
In a further aspect 7 this invention prov.id,es a process for the preparation of 3 fluid pharmaceutical formulation which pro-cess comprises mixing a medieament with a dispersion of an oleophilic clay in an edible oil.
If a polar solvent is to be used, it is normal to add the solvent to the dispersion of the clay in the oil before the mixing step with the medicament is carried ou-t. Also, if a natural or synthetic clay absorbent is to be used, it is normally mixed into the dispersion of the cl~y- in oil at the same time as the medicament.
- The clay in oil dispersion, optionally containing the polar solvent, is preferably passed through a c'olloid mill before it is mixed with the medicament and optional natural or synthetic clay absorbent,. Si,nilarly the final,suspension is preferably passed thro~gh a colloid mill before use.
The invention also provid~s a method of preYenting or treating a disease .in domestic animals, which method ... ``'.... ," ' ' ' : .
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106261~
comprises the oral administration of a fluid pharmaceutical - formulation as hereinbefore defined. The formulation 13 normally a~ministered by means of a sui.table dispenser, such as a nozzle connected to a bottle and plunger. A single dose 5 may be for example 1 to 10 mls. of the suspension, containing a concentration of medicament which is in accordance with the recommended dosage of that medicament.
The formulation of the invention containing an ap~ropriate medicament is of particular use ln the treatment of ani~al diar-rohoea or scours, and in particular in the treatment of neonatal - scours in piglets.
The following Examples illustrate the invention:
Exam~
. _ The following formulation was prepared by the method set out below:
Bentone*38 (1). 1.5% w/v Propylene Carbonate 0.6~ w/v Pharmasorb*(2) 10~ w~v Phosphoric Acid (3) 0.1% w/v :
Ampicillin Trihydrate 6.0% w/v as free acid Soya-bean Oil to 1009~
(1) Bentone 38 is dimethyl dioctadecyl ammon.ium hectorite, [Mg8 LiSi12030(0H)6~CH3)2N(c18H37)2~

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* Trade Mar2) Pharmasorb is a brand of activated Attapulgite, Attapulgite ~
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havin~ the al~proximate composition as defined earlier in the - specification.

(3) The phosphoric acîd is present in a minor proportion to balance the alkaline pH of the Bentone.
The Bentone*was dispersed in the soya-bean oi3., and when thoroughly distributed, the propylene carbonate was added with high speed mixing, followed by colloid milling to produce the base. Into this base was first mixed the phosphoric acid, and then the pha~nasorb and the penicillin, and the resultant 10- suspension was then passe~ through a colloid mill once more.
Example ?
Example 1 was repeated, but using amoxyclllin trihydrate in place of the ampicillin trihydrate.
Exam~le ~
The foliowing formu?ation was prepared by the method of Ex~mple 1:
Bentone*27 ~1) 1.755~ w/v Propylene Carbcnate 0.6% w/v Pharmasorb* 10.0,S w/v Ampicillin Trihydrate 5.0% w/v Sunflower Oil to 100%
(1) Bentone* 27 i~ dimethyl benzyl octadecyl ammonium hectorite, 8Lisi12o3o((~H)~c~3)2N(518D37)(cH2c6H5)l, "

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' . , 1~62614 Exampl e 11 Example ~ was repeated, but u~ing amoxycillin trihydrate in place of the ampicillin trihydrate.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A fluid pharmaceutical formulation for oral administration to animals which formulation comprises an antibiotic, an edible oil and a natural or synthetic clay in which inorganic cations have been replaced by organic cations in order to render the clay more dispersible in the edible oil.

2. A formulation according to claim 1, wherein the inorganic cations of the clay have been replaced by ammonium ions substituted by at least one C12-18 alkyl group.

3. A formulation according to claim 2, wherein the substi-tuted ammonium ions are of formula (I):

(I) wherein R1 is a C12-18 alkyl group, R2 is either a second C12-18 alkyl group, a benzyl group, a C1-6 alkyl group, or hydrogen, and R3 and R4 are each a C1-6 alkyl group or hydrogen.

4. A formulation according to claim 3, wherein R1 is a C15-18 alkyl group, R2 is a C15-18 alkyl group or a benzyl, methyl or ethyl group or hydrogen, and R3 and R4 are each a methyl or ethyl group or hydrogen.

5. A formulation according to claim 2, wherein the substi-tuted ammonium ions are octadecyl ammonium, dimethyl mono- or di-octadecyl ammonium dimethyl hexadecyl ammonium or dimethyl benzyl octadecyl ammonium ions.

6. A formulation according to claim 2, 3 or 5 wherein the natural or synthetic clay is a montmorillonite.

7. A formulation according to claim 2, 3 or 5 wherein the natural or synthetic clay is a hectorite.

8. A formulation according to claim 2, 3 or 5, wherein the natural or synthetic clay is a hydrated magnesium aluminium silicate of the montmorillonite group of clays, but containing a higher magnesium content than normal montmorillonites and containing traces of calcium and iron.

9. A formulation according to claim 1, 2 or 3 wherein the edible oil is sunflower oil, arachis oil, soya-bean oil, rapeseed oil or maize oil.

10. A formulation according to claim 1, 2 or 3 wherein the anti-biotic is cloxacillin, fluoloxacillin, or the 5-indanyl or phenyl ester of carbenicillin.

11. A formulation according to claim 1, 2 or 3 wherein the anti-biotic is ampicillin.

12. A formulation according to claim 1, 2 or 3 wherein the anti-biotic is amoxycillin.

13. A formulation according to claim 1 wherein the antibiotic is present as 1 to 15% of the formulation.

14. A formulation according to claim 13, wherein the antibiotic is present as 3 to 10% of the formulation.

15. A formulation according to claim 1 wherein the oleophilic clay is present as 0.1 to 25% of the formulation.

16. A formulation according to claim 15, wherein the oleophilic clay is present as 1 to 5% of the formulation.

17. A formulation according to claim 16, wherein a polar solvent is present as 0.1 to 2.0% of the formulation.

18. A formulation according to claim 17 wherein the polar solvent is propylene carbonate.

19. A formulation according to claim 1, 2 or 3 wherein a natural or synthetic clay absorbent is present as from 1 to 20% of the formulation.

20. A formulation according to claim 1, 13 or 15 wherein the edible oil comprises at least 50% of the formulation.

21. A process for the preparation of a fluid pharmaceutical formula-tion for oral administration to animals comprising an antibiotic, an edible oil and a natural or synthetic clay in which inorganic cations have been replaced by organic cations in order to render the clay more dispersible in the edible oil which process comprises mixing the medicament with a disper-sion of the clay in the edible oil.

22. A process according to claim 21, wherein both the dispersion and the final formulation are passed through a colloid mill.

23. A process as claimed in claim 21 or 22, wherein a polar solvent is mixed into the dispersion before addition of the antibiotic, and a natural clay absorbent is mixed into the dispersion at the same time as the antibiotic.