AU628211B2

AU628211B2 - Stable injectable pharmaceutical formulation for folic acid and leucovorin salts and method

Info

Publication number: AU628211B2
Application number: AU61165/90A
Authority: AU
Inventors: Bruce Edwin Haeger
Original assignee: American Cyanamid Co
Current assignee: Wyeth Holdings LLC
Priority date: 1989-08-21
Filing date: 1990-08-20
Publication date: 1992-09-10
Anticipated expiration: 2010-08-20
Also published as: JPH0390026A; DE69021673T2; DK0416232T3; PT95026A; CA2023563C; ES2076263T3; KR910004194A; EP0416232A2; EP0416232B1; DE69021673D1; AU6116590A; CA2023563A1; JP3043381B2; ATE126438T1; KR0159768B1; PT95026B; GR3017143T3; EP0416232A3

Abstract

Injectable aqueous compositions comprising folic acid and leucovorin and their salts, optionally including benzyl alcohol, sodium chloride and agents for adjusting pH are stabilized and buffered in the range of 6 to 10 by adding a combination of tromethamine and monothioglycerol. Such compositions remain stable for prolonged periods even when exposed to sunlight.

Description

ixi II i 628211 S F Ref: 135391 FORM COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Class Int Class Complete Specification Lodged: Accepted: Published: Priority: Related Art: t Name and Address of Applicant: Address for Service: American Cyanamid Company One Cyanamid Plaza Wayne New Jersey 07470 UNITED STATES OF AMERICA Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Complete Specification for the invention entitled: Stable Injectable Pharmaceutical Formulation for Folic Acid 4 and Leucovorin Salts and Method The following statement is a full description of this invention, including the best method of performing it known to me/us 5845/5 r 30,678-00 t~* 0 000 o 00 0 0 0 OCt00 0000*9 0 0 000,00 0 0 0 00 0 0000 STABLE INJECTABLE PHARMACEUTICAL FORMUTLAT ION FOR FOLIC ACID AND LEUCOVORIN SALTS AND M.ETHOD

ABSTRACT

Injectable aqueous compositions comprising folic acid and leucovorin and their salts, optionally including benzyl alcohol, so(,Ium chloride and agents for adjusting pH are stabilized and buffered in the range of 6 to 10 by adding a combination of tromethamine and inonothioglycerol. Such compositions remain stable for prolonged periods even when ex-posed to sunlight.

00*0 a 0 30,678 STABLE INJECTABLE PHARMACEUTICAL FORMULATION FOR FOLIC ACID AND LEUCOVORIN SALTS AND METHOD The present invention relates to new improved injectable compositions comprising folic acid salts and leucovorin salts. More particularly, it relates to compositions comprising folic acid salts and leucovorin salts that remain stable for prolonged periods under normal storage conditions because they include tromethamine and monothioglycerol as a buffering agent/antioxidant combination.

BACKGROUND OF THE INVENTION Folic acid and its salts and leucovorin and 4 o° its salts are known to be pharmaceutically effective.

See, Remington's Pharmaceutical Sciences, Seventeenth Edition, Mack Publishing Co., Easton, PA 1985 o 4 (Remington's 17th Ed.) p. 1023. Folic acid is used to treat vitamin deficiencies. Cosulich, U.S. 2,688,018 g.o describes the preparation of such compounds and their clinical use for controlling the toxicity of aminopterin and other antifolic acid compounds and as hematopoietic drugs. Active derivatives of such compounds are described in Shive, U.S. 2,741,608. In U.S. 4,500,711, a* Wisowaty et al., describe the purification of leucovorin and its salts. Kerwar et al., U.S. 4,746,662 disclose that the antiarthritic efficacy of methotrexate can be potentiated by injection of an aqueous solution of leucovorin or its c-alts. EPO Pate ntD Duli ion 0,266,042, May 4, 1988, describes using pure leucovorin isomers to manufacture medicaments for methotrexate rescue, for treatment of colorectal cancer in combination with 5-fluorouracil, and for treating folate deficiency.

Both folic acid and leucovorin are only sparingly soluble in water. Therefore they are administered in the form of salts such as alkaline metal and alkaline earth metal salts, such as the sodium, salt of folic acid and the calcium salt of leucovorine the 1-isomer of the latter being preferred.

The compound (2-Amino-l,4-Dihydro-4-oxo- 6-pteridinyl)methyl)-amino)benzoyl)-L-glutamic acid, sodium salt (Sodium Folate) having the formula

H

II

0 CH.,NH- /a CONH ::HOOCCH 2 C COOH is used principally to stimulate specifically the production of red blood cells, white blood cells and platelets in persons suffering from certain megaloblastic anemias.

The compound ((2-Amino-5-formyl-l,4,5, 6,7, 8-hexahydro-4-oxo-6-pter idinyl) methyl) amino) benzoyl) L-glutamic acid, calcium salt pentahydrate, (Leucovorin Calcium liSP) having the formula: 0 0 H H0 H 2N lI hI 2IY N YN II I CH NH /\CONH *H2 0 CHO 2 CaOOCCH 2 CH- C----COOCa I r i I r -3is used principally as an antidote for folic acid antagonists such as methotrexate, which block the conversion of folic acid into folinic acid. Merck Index, Tenth Edition, p. 603. Both folic acid and leucovorin salts are formulated in water for injection and may contain suitable preservatives, as described under Folvite* Injection and Leucovorin Calcium Tnjection in the Physician's Desk Reference, Medical Economics Company, Oradell, NJ 1989 (PDR) pp. 1120 and 1124, respectively.

Both compounds, but especially Leucovorin Calcium, require an alkaline pH of 7.7-8.2 for maximum stability. They are also light sensitive and prone to o oxidative degradation in aqueous solution, thus 15 requiring the use of. amber glass for protection against photosensitivity and the use of nitrogen gas as a protectant throughout the bulk liquid manufacturing process and as a package headspace gas.

In the past, methyl and propyl parabens (p-hydroxy benzoates) were used as a preservative for such salts, especially Leucovorin Calcium Injection.

However, the parabens were later found to have short term effectiveness at the alkaline pH required for S maximum folic acid and/or leucovorin stability.

Subsequently, benzyl alcohol was approved and widely used as the new preservative for the products. See "Folvite* Folic Acid Solution" and "Leucovorin Calcium Injection", PDR, pp. 1120 and 1124 respectively.

Although benzyl alcohol is errective as a preservative, it lacks the mild buffering activity afforded by the parabens. As a consequence the pH of the products tend to be somewhat unstable, slowly drifting downward with time toward pH 6.5-7.0. This is below the above-mentioned optimum range and may require expiration dating to be -I I r -4very short term.

It has now been found that the factors of pH drift, nitrogen headspace variability and short term expiry dating can be overcome in accordance with this invention by using a buffer/antioxidant combination.

The buffer comprises 2-Amino-2-(hydroxymethyl)-l, 3-propanediol,also known as tromethamine. The antioxidant comprises 3-Mercapto-l,2-propanediol, also known as monothioglycerol.

Both compounds, tromethamine and monothioglycerol, are toxicologically acceptable, and are described in U.S. Pharmacopeia XXI, U.S. Pharmacopeial Convention, Rockville, MD 1985 XXI) at pages 1102 and 1580, respectively.

Surprisingly, the new buffer/antioxidant S compositions of the present invention, for tromethamine Sand monothioglycerol, have been found to be superior to S* the presently used formulations, in terms of ability to control pH in the desired region of folic acid and leucovorin stability, and in their ability to retard oxidation, and therefore degradation, in sealed dosage forms. These new buffer/antioxidant compositions make it possible to extend the expiry dating of the product o and provide the potential for development of a broader dosage line for such products, e.g. single or multi-dose vials containing greater volumes and higher concentrations of either folic acid or leucovorin salts than the present single dose (3-5 mg/ml) ampuls, such as a t mg/ml, 100 mg/vial dosage preparation. Unexpectedly 0 also, enzyl alcohol becomes an optional ingredient and thi- .s desirable expecially in cases where large doses are needed in emergencies and too much benzyl alcohol is not recommended.

I I I I

I

IItr SUMMARY OF THE INVENTION According to the present invention there are provided stable, injectable aqueous compositions comprising an effective amount of water-soluble pharmaceutically-acceptable salt of folic acid or leucovorin; 7 (ii) -amma. effective preservative amount of benzyl alcohol; and (iii) an effective amount of a buffer/antioxidant combination comprising tromethamine and (b) monothioglycerol, said combination (iii) being present in an amount at least sufficient to maintain the pH of said composition in a predetermined range of from about 15 6 to about 10 and to protect the composition against degradation induced by oxygen or light.

In preferred embodiments, the compositions comprise those wherein said salt comprises a salt of dl-leucovorin; those wherein the compositions also include (iv) sodium chloride in an amount sufficient to render said composition isotonic; those which also include a pH adjustor comprising an acid or a base in amount sufficient to adjust the pH to any value within said range; those wherein said pH adjustor 25 comprises hydrochloric acid or sodium hydroxide.

Especially preferred are compositions wherein said 1-leucovorin salt comprises calcium leucovorin. Special mention is made of a formulation comprising from 3 mg/ml to 25 mg/ml of calcium leucovorin in an isotonic 30 solution at a pH of from 6.5 to 8.5, with or without benzyl alcohol at a concentration of from 0.0% w/v to 0.909% w/v, TRIS (tromethamine) at a concentration of from 0.10% w/v to 0.30% w/v, monothioglycerol at a concentration of from 0.10% w/v to 0.30% w/v; sodium 4I*4 o 4 IIr

II.

II

I -6chloride at a concentration from 0.45% to 0.65% w/v, with hydrochloric acid at a concentration of from v/v% to 10.0 v/v% and sodium hydroxide at a concentration of from 1.0 w/v% to 5.0 w/v% added as required to adjust the pH; and particularly those in which the concentration of calcium leucovorin on the one hand is 3.0 mg to 3.54 mg/ml and 10 mg to 11 mg/ml, on the other, and the concentrations of benzyl alcohol, TRIS (tromethamine), monothioglycerol and sodium chloride are from 0.765% w/v to 1.035% w/v, 0.150% w/v, 0.200% w/v and 0.560% w/v, respectively.

The present invention also contemplates a method for stabilizing compositions as above defined o .o comprising adding thereto an effective amount of the buffer/antioxidant combination comprising tromethamine and monothioglycerol.

DETAILED DESCRIPTION OF THE INVENTION o S° The injectable composition of this invention can be prepared by techniques well known to those skilled in the art of pharmaceutical formulation. The substantially pure salts may be prepared, mixed with the other components, filtered, filled into containers, and sealed under aseptic conditions.

Folic acid and its salts can be prepared by any convenient method, for example *0 0 2,3-dibromopropionaldehyde, dissolved in a water miscible organic solvent (alcohol, dioxane), is added to a solution of equal molecular quantities of 2,4,5-triamino-6-hydroxypyrimidine and p-aminobenzylglutamic acid, maintaining a pH of about 4 by the controlled addition of alkali as the reaction progresses.

If sodium hydroxide is used as the alkali, sodium folate is obtained. To make calcium leucovorin, folic acid is, for example simultaneously hydrogenated and formylated -7in 90 to 100% formic acid under the influence of platinum oxide catalyst to yield leucovorin. Conversion to the calcium salt may be accomplished by dissolving the leucovorin in sodium hydroxide solution, treating the calcium chloride, and precipitating with ethanol.

Benzyl alcohol is an item of commerce and, if used, is widely available from a number of sources (Remington's 17th Ed. p. 1057).

1,3-Propanediol, 2-amino-(2-hydroxymethyl)- (tromethamine) is available commercially (Remington's 17th Ed. p. 836). It can be made by additively reacting nitromethane with formaldehyde to yield tris (hydroxymethyl) nitromethane, and the nitro compound is o then hydrogenated with Raney nickel in accordance with So. 15 U.S. 2,174,242.

3-Mercapto-l ,2-propanediol (monothioglycerol) S is readily made, for example, by heating an ethanolic o" solution of 3-chloro-l,2-propanediol with potassium bisulfite (Remington's 17th Ed. p. 1279).

The amounts of the respective components can vary fairly broadly, within conventional limits well known to those skilled in this art. Preferred embodiments will be exemplified hereinafter. Typically o b" the folic acid salt or leucovorin salt will comprise from about 0.5 to 50 mg/ml, preferably from about 1 to about 35 mg/ml and especially preferably from about 3 to about 25 mg/ml. With folic acid sodium salt, special mention is made of 5 mg/ml and for calcium leucovorin, 3 mg/ml.

Benzyl alcohol can be omitted, but if present, can comprise up to about 2.5 percent w/v, preferably up to 1.5 percent w/v with sodium folate and up to about 0.909 percent w/v with calcium leucovorin.

The amounts of tromethamine and monothioglycerol

~----~C"~LIIIIIIIILII

-8relative to each other can vary broadly, from about 1 to 99 parts by weight, preferably from about to about 80 parts by weight of the formet to from about 99 to 1 parts by weight, preferably from about 80 to about 20 parts of the latter. Preferably the tromethamine and monothioglycerol each will comprise from about 0.05 percent w/v to about 0.6 percent, preferably from about 0.1 to about 0.3 percent w/v of the composition. If sodium chloride is present, it can range from 0.1 to about 1.0 percent, preferably from about 0.45 to about 0.65 percent w/v. The pH adjustors can vary widely in type and amount. Typically hydrochloric acid, percent v/v and sodium hydroxide 4.0% w/v will be S, conveniently employed.

'15 The injectable solutions prepared as described above and more fully exemplified hereinafter are used in conventional dosages. A typical daily dose is generally a'n up to about 150 mg, in the range of from about S, to 150 mg which is conveniently administered in divided doses, for example 2, 3 or 4 doses in a 24 hour period (methotrexate rescue with calcium leucovorin injectable).

For treating folate deficiency lower doses of leucovorin are generally administered. For example, a typical daily dose for an adult human-is generally in 2 5 the range of 2 to 25 mg which may be conveniently administered as a single dose (leucovorin calcium) or up to 1=0 mg daily (sodium folate).

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following examples illustrate the invention but are not intended to limit the claims in any manner whatsoever.

In the data tables, the following abbreviations have the following meanings:

I

-9- RT room temperature M month PABG N-(p-aminobenzoyl)glutamic acid FFA (N 1 0 -formyl folic acid) Leucovorin Potency leucovorin calcium (as free acid) %LP percent of label potency based on label potency of leucovorin NMT not more than RHC 37 0 C and 75% relative humidity in closed containers SUN exposure to sunlight ND none detected RH relative humidity LCAB light cabinet having 1,000 footcandle intensity 0 0 EXAMPLE 1 Leucovorin calcium salt is used as the active S ingredient in a composition for injection having the S* formula set forth in Table 1: S 4 .1 i 4 0 4 4 4 F a 4. SO 4e e o4 a, S- 4 Ia TABLE 1. COMPOSITON FOR INJECTION COMPRISING LEUCOVORIN CALCIUM Ingredient Leucovorin Calcium U.S.P.

Benzyl Alcohol-Reagent Grade Tromethamine-Reagent Grade Monothioglycerol N.F.

Sodium Chloride-Reagent Grade Hydrochloric Acid-Reagent Grade Sodium Hydroxide USP Water for Injection U.S.P.

Nitrogen PrepLrified w/v 0.330* 0.909 0.150 0.200 0.560 pH 8.0-8.2 pH 8.0-8.2 100.0(v/v) Function in Composition Active Ingredient Antimicrobial Preservative Buffer Antioxidant Tonicity Adjuster pH Adjuster pH Adjuster Vehicle Protectant** qs ad qs ad qs ad Based on Leucovorin Anhydrous Free Acid at 100% Used as a protective gas to retard oxidation of the product during manufacture, and as a headspace gas in the final sealed package.

-11- The formulation is prepared as follows: A. Production of Bulk Solution Water for Injection, representing approximately of final batch volume, is added to a stainless steel mixing tank. The Water for Injection is sparged with nitrogan until the water temperature has reached 25-30 0 C. (The product is continuously sparged or blanketed with nitrogen throughout the remaining process to protect against oxidation). The ingredients are sequentially added, mixed and dissolved in the following order: benzyl alcohol; sodium Schloride; tromethamine; monothioglycerol; and S« calcium leucovorin. The pH is then adjusted to 8.1 0.1 with 5% hydrochloric acid and/or 1% sodium hydroxide. The batch is brought to a final volume of 20-30 liters with Water for Injection sparged with nitrogen. The pH is re-checkeJ and re-adjusted to 8.1 0.1 with hydrochloric acid or sodium hydroxide if necessary.

aa B. Production of Sterile Filtrate Prior to the sterile filtration, a 0.2 micrometer filtration cartridge is tested for integrity by Bubble Point testing at a pressure of 30 psig. The bulk solution is then passed through a first stage pre-filtration unit containing an AW19/0.45 micrometer cartridge to an in-series sterile 0.2 micrometer second stage cartridge. Pump and Nitrogen gas pressure feed the solution through the filtration units to a tared 4 I 1 -12sterile stainless steel collection drum.

At the completion of filtration the 0.2 micrometer filtration unit is again tested for integrity by Bubble Point testing at 35 psig.

Elastomeric silicone tubing is used for all product transfer.

C. Production of Filled Product The bulk sterile solution is taken to a class 100 filling area where it is pumped from the collection drum through a sterile 5 micrometer filter to a filling line surge bottle. It is fed from the surge bottle to filling needles which eject measured doses to conveyor fed ampuls and vials. (Two filling lines, one for each package style, are used).

0 a 15 ooo o t'000 0 4 4 L 9 0C 0000 0009 O 0 04 0I 00 4 O Icc Amber glass ampuls are filled at 1.15 0.05 ml (1.0+0.15+0.05 ml USP overage). 10cc Type 1 amber glass vials are filled at 10.5 ml (10.0 0.5 ml USP overage). All ampul and vial fills receive a nitrogen headspace blanket prior to sealing. Ampuls are heat sealed in a gas flame, and vials are sealed with butyl closures and aluminum crimp seals.

EXAMPLES 2 AND 3 A second batch (Example 2) corresponding to Example 1 is prepared by the method described in Example 1 as in Table 1. A third batch (Example 3) is prepared, but this is 30 liters in size instead of 20 liters, as shown in Table 1.

COMPARATIVE EXAMPLE 1A A formulation like Example 1 without tromethamine and monothioglycerol having the formula set forth in Table 2 is included for comparison purposes: a 4 4 4 o 4 a a 0 0 a a a a a o a 4; a a a a 0& a a pa a P a Se *~a a *a *a P 5 *a a a 40 aa V a 4 0 a a C. 0 a a 4 a a 0 P.O Ca. a TABLE 2. COM4POSITION FOR INJECTION COM4PRISING CALCIIIM-LEUCOVORIN I ng red ient W/V Function in Comp~osition Leucovorin CalciLim EJ.S.P.

Benzyl Alcohol-Reagent Grade Sodium Chloride-Reagent Grade Sodium Hydroxide-N.F.

Hydrochloric Acid-Reagent Grade Water for Injection U.S.P.

Nitrogen Piepurified 0.270-0.330* 0.90 0.0-0.560 pH 7.7+0.2 pH 7.7+0.2 100.0 (v/v) qs ad qs ad qs ad Active Ingredient Preservative Tonicity Adjuster pH Adjuster pH Adjuster Vehicle Protectant** Based on Leucovorin Anhydrous Free Acid at 100%.

**Used as a protective gas to retard oxidation of the product during manufacture, and as a headspace gas in the final sealed package.

V

I

t i -14- The general procedure of Example 1 is used to make filled dosage forms comprising the following: Batch 1A 2A 3A 4A Ingredient w/v w/v w/v w/v Calcium Leucovorin (As Free Acid) 0.30 0.27 0.27 0.33 Benzyl Alcohol Regeant 0.90 0.90 0.90 0.90 Sodium Chloride 0.56 0.56 Sodium Hy roxide Solution q.s. q.s. q.s. q.s.

Hydrochloric Acid 1.0% q.s. q.s. q.s. q.s.

15 Solution-Adjust to pH 7.7 4 A Water for Injection qs ad 100 100 100 100 Amber glass ampules are the containers selected for filling.

*o COMPARATIVE EXAMPLES 2A, 3A and 4A A second, third, and fourth batch of formulae S without tromethamine and monothioglycerol are prepared for comparative testing using the general procedure for Example 1.

ii I The filled dosage forms from Examples 1-3 are placed on an accelerated stability test. The analytical methodolgy is as follows: Analytical Methodology used for Examples 1-3 t Method Test Description Leucovorin potency Leucovorin related compounds potencies Benzyl Alcohol pH USP Particulate Matter Monothioglycerol (Identification) S Microbiological evaluation of preservative system visual High pressure liquid chromatography (HPLC)

(HPLC)

Gas Chromatography pH meter USP XXI Particulate Matter, Injections, light obscuration Gas Chromotography Antimicrobial Preservative Effectiveness test USP XXI pp 1151-1156.

The results of the tests performed on the packaged formulations of Examples 1-3 are reported in Tables 3, 4 and 5, respectively: II L t t Ir f 0 aa sea *0 55 A *0 00 0 4 0 a a 0 0 4 *00 0

I

Table 3. ThreeMonth Accelerated and Six Month Room Temperature Stability Data on Leucovorin Calcium Injection Solutions 3 mg/mi (Example 1) Amber Ampul Packaging Storage Condition Leucovorin Po ten cy

%L.P.

Ben zy 1 Alcohol

%L.P.

Folic Acid

%L.

Other Related Compounds

%L.

PABG

%L.

F FA

%L.

pH Descrciption Specification

NMT

B85-115% 1.0% 100-118% NMT NMT 1.0%

NMT

2.5% (2) Clear' Light 6.5-8.5 Yellow Solution Initial RT, 3M RT, 6M RFIC-1M RHC-2M RHC-3M SUN-lM 0.25

ND

0.36 0.39 0.45

ND

0.39 0.72 1.16 1.56 1.50 2.24 2.36 1.12 0.35

ND

0.23 P. 37 0.39

ND

0 ,23 1.35 1.91 2.18 1.82 2.80 2.21 2.98 7.93 7.92 7.97 7.74 7.77 7.90 7.78 Clear Light Yell~ow Solution I Not more than 1.3% for initial release and based on the label claim of leucovorin.

not more than 3.5% for shelf life Not more than a sum of 2.5% for initial releas'e and not more than as PABG based on the label claim of leucovorin.

3.5% for shelf life a a a 0 a S 4 4 a. a 4 a. a a a, baa o St *4 4 4 *4 4 4 *a *0 a a a a a C 'a a 5.9 aaa 0 a Table 3. (continued) Amber Ampul Packaging Other Leuco, orin Benzyl Folic Related Storage Potency Alcohol Acid PABG FFA Compounds pH Description Condition %L.

Specifi- NMT NMT NMT NMT Clear Light cation 100-118% 85-115% 1.0% 1.0% 6.5-8.5 Yellow solution Initial 109 99 0.25 0.72 0.35 1.35 7.93 Clear Light Yellow Solution RT, 3M 104 io0 ND 1.22 ND 1.49 7.90n RT, 6M 105 97 ND 1.64 0.34 2.05 7.92 RHC-1M 105 98 0.36 1.54 0.30 2.26 7.75n RHC-2M 103 99 ND 2.34 ND 1.75 7.86 RHC-3M 102 100 ND 2.59 ND 1.81 7.88n SUN-iM 106 99 0.35 1.13 0.38 2.14 7.77 t Not more than 1.3% for initial release and based on the label claim of leucovorin.

not more than 3.5% for shelf life Not more than z, sum of 2.5% for initial release and as PABG based c'n the label claim of leucovorin.

not more than 3.5% for shelf life bb- Table 4. Three Month Accelerated and Six Month Room Temperature Stability Data on Leucovorin Calcium Injection Solutions 3 mg/mg (Example 2) Amber Ainpul Packaging S to rage Condition Leucovorin Potency

P.

Benzyl Alcohol

%L.P.

Folic Acid

%L.

PABG

%L.

Other Related Compounds

%L.

PH Description Specif ication Initial RT, 3M RT, 6M RH C-l 1.

RHC-2M RHC-3M SUN-lM

NMT

85-115% 1.0% NMT NMT 1.0%

NMT

2.5%(2) Clear Light 6.5-8.5 Yellow Solution 100-118% 0.20

ND

0.27 0.05 0.40

ND

0.05 0.52 0.80 1.36 1.44 2.04 1.70 1.01 0.22 0.18 0.25 0.31 0.28 0.22 0.14 1.30 1.49 1.74 2.01 2.32 1.81 z.09 7.94 7.90 7.97 7.76 7.91 7.90 7.78 Yellow Solution to Not more than 1.3% for initial release and based on the label claim of leucovorin.

not more than 3.5% for shelf life Not more than a slum of 2.5% for initial release and not more than life as PABG Lased on the label claim of leucovorin.

3.5% for shelf 11&- r--v Get C a 0e C *fl 9 V S 9 a, a Table 4. (continued) Amber Ampul Packaging Storage Condition Specification Leucoior in Potency

P.

100-1 L8% Benzyl Alcohol

%L.P.

Folic Acid

%L.

PABG

%L.

FFA

%L.

Other Related Compounds

UL.

PH Description

NMT

85-115% 1.0% NMT NMT 1.0%

NMT

2.5% (2) Clear Light 6.5-8.5 Yellow Solution Initial RT, 3M RT, 6M RHC -l M RHC-2M RHC-3 M

SUN-IM

0.20

ND

0 .35

ND

0.25 0.36 0.52 0.93 1.43 1.47 2.12 2.03 1.05 0.22 0.26.

0.28 0.23

ND

0.32 0.28 1.30 1.91 1.98 1.79 1.63 2.21 2.00 7.94 7.91 7.89 7.74 7.87 7.86 7.76 Clear Light Yellow Solution nfI Not more than for initial release and based on the label claim of leucovorin.

not more than 3.5% for shelf life Not more than a sum of 2.5% for initial release and life as PABG base~d on the label claim of leucovorin.

not more than 3.5% for shelf 9 0 C 9 0 cOo 9 *9 £4 4 c oc 0 4 S 444 cc 0 90 0 94 094 9 Cc 94 9 9 cc c c cc 00 cc 0 9 c 4 4 o c c 3 4 cc c 9 949 944 4 9 Table 5. Three Month Accelerated and Six Month Room Temperature Stability Data on Leucovorin Calcium Injection Solutions 3 mg/mi (Example 3) Amber Ampul Packaqinq Other Leucov~orin Benzyl Folic Related Storage Potency Alcohol Acid PABG FFA Compounds PH Description Condition %L.

Specifi- NMT NMT NMT NMT Clear Light cation 100-118% 85-115% 1.0% 1,0i 6.5-8.5 Yellow Solution Initial 108 100 0.46 0.68 0.27 1.04 8.09 Clear Light Yellow Solution RT, 3M 108 101 0.44 1.02 0.08 1.47 7.98 I RT, 6M 103 99 0.66 1.36 ND 1.78 8.00 RHC-1M 107 98 0.49 0.89 0.15 1.81 7.95 RHC-2M 105 101 0.54 0.96 0.26 2.24 7.96 R11C-3M 108 99 0.52 1.08 0.10 1.55 8.00 SUN-lM 107 98 0.49 0.88 0.15 1.80 7.96 1) Not more than 1.3% for initial release and based on the label claim of leucovorin.

not more than 3.5% for shelf life 2) Not more than a sum of 2.5% for initial release and not more than life as PABG based on .the label claim of leucovorin.

3.5% for shelf 1 rrC-

C

II

Table 5. (continued) Amber Ampul Packaging Other Leucovorin Benzyl Folic Related Storage Potency Alcohol Acid PABG FFA Compounds pH Description Condition %L.

Specifi- NMT NMT NMT NMT Clear Light cation 100-118% 85-115% 1.0% 1.0% 6.5-8.5 Yellow Solution Initial 108 100 0.46 0.68 0.27 1.04 8.09 Clear Light Yellow Solution RT, 3M 107 98 0.54 1.16 0.12 1.51 7.96 RT, 6M 103 98 0.92 1.41 0.34 1.88 8.00 RHC-1M 107 98 0.48 0.96 0.24 1.41 7.95 RHC-2M 106 100 0.52 1.01 0.23 1.94 7.96 RHC-3M 108 101 0.47 1.10 0.10 1.50 7.98 SUN-IM 105 99 0.51 0.98 0.17 1.48 7.96 1) Not more than 1.3% for initial release and not more than 3.5% for shelf life based on the label claim of leucovorin.

2) Not more than a sum of 2.5% for initial release and not more than 3.5% for shelf life as PABG based on the label claim of leucovorin.

1 I -22- The effectiveness of the preservative system of this invention for Leucovorin Calcium Injectable Solutions, Examples 1-3, is tested in accordance with the Antimicrobial Preservatives Effectiveness Test outlined in U.S. Phamacopeia XXI, pages 1151-1156. This provides a measure of the capacity of the solutions to decrease microbial growth when individually challenged with Staphylococcus aureus, Escherichia coli, Psuedomonas aeruginusa, Candida albicans and Aspergillus niger at a dose level of 100,000 to 1,000,000 microorganisms per ml. The contaminated solutions are stored and sampled at a series of time intervals in order to obtain microorganism counts. The results of these tests, set forth in Tables 6, 7 and 8, indicate that the benzyl S 15 alcohol prevents the growth of microorganisms, and a provides qualities necessary to pass the anti-microbial preservative effectiveness test.

4 to 4 *4 '~a ~1

L

b 8 *0 8.0 p bt C C P *8 8 8 P 889 8 00 0 84 8p0 88 *8 8 0 a~ 8 8 S 0 8 8 00 0 4 0 88;.

08* *8.

Table 6. Microbiological Evaluation of Presetrvative System U.S.P. XXI Method Example 1 Inoculation Organism Count 1 Week 2 W2eks 3Weeks 4 Weeks Staphylococcus aureus 108,500 <10 <10 <10 Escherichia coli 108,500 <10 <10 <10 Pseudomnonas aeruginosa 105,500 <10 <10 <10 Candida albicans 285,000 5,800 <10 <10 Aspergillus niger 610,000 1,900 <10 <10 q- 60 0 60 0 00 000 06 0 0 a a, 0 4*0 ao 4 C 00 Table 7. Microbiological Evaluation of Preservative System IJ.S.P. XXI Method Example 2 Inoculation Organism Count 1 Week 2 Weeks 3 Weeks 4 Wee) s Staphylococcus aureus 108,500 <10 5 10 Escherichia coli 108,500 5 <10 <10 Pseudomonas aeruginosa 105,500 <10 <10 <10 Candida albicans 285,000 9,300 <10 <10 ?spergillus niger 610,000 2,000 <10 <10 4 4 0* C C CC *9* 0* 40 4 4 'Table G. Microbiological Evaluation of Preservative System U.S.P. XXI Method Exam ple 3 Inoculation Organism Count 1 Week 2 Weeks 3 Weeks 4 Weeks Staphylococcus aureus 108,500 <10 10 5 Escberichia coli 108,500 <10 <10 10 Pseudomonas aeruginosa 105,500 <10 <10 <10 Candida albicans 285,000 9,550 <10 <10 Aspergillus niger 610,000 190 <10 <10

I

-26- The storage stability and microbiological testing of the injectable leucovorin calcium preparations set forth under Comparative Examples 1A, 1B, I' and 1D using standard test methods are determined by the following procedures: Test Description Leucovorin potency Benzyl Alcohol Method Visual Thin layer Chromatography Spectlophotometric Gas Liquid Chromatography PH meter! boo* 0 09 00 Microbiological evaluation of preservative system Antimicrobial Effectiveness Test USP XIX page~ 587 Stability data for the comparison calcium injection compositions are set forth in Tables3 9, 10 and 11: Table 9. MEAN ASSAY YIELDS, EXPRESSED AS PERCENT LABEL POTENCY FOR LEUCOVORIN CALCIUM (AS FREE ACID) Example 1A 2A 3A 4A LP LP LP LP Label Potency (In ig) of Leucovorin 3.0 2.7 100 2.7 100 110 Theory 100 Initial 0 1W 2W 56-C., 2W 56 0 114 56-C., 2M 42 0 1M 42 0 2 M 42 0 C. ,4M4 105 107 103 99 105 101 99 106 107 98 i -27- Example 42 0 C. 5M RT, 3M RT, 4M RT, 6M RT, 7M RT, 9M RT, RT, 11M RT, 13M RT, 16m RT, 22M RT, 29M RT, 30M Sun 1M Table 10.

Table 9.

IA

LP

92 (continued) 2A

LP

3A

LP

4A

LP

98 102 97 106 107 A IA 04 0

A

AA

A A A 4044 o A 9441404 A A A 41 A 0 9 4440 A Al A A A 00#* AA A A A A A AA A Al 00 9 4* A 14 A A 4 0414 4 96 97 MEAN ASSAY YIELDS, EXPRESSED AS I POTENCY FOR BENZYL ALCOHOL 1A 2A 3A LP LP LP 100 ~ERCENT [LABEL Example Label Potency (In mg) Theory initial 70 0

C.,

56-C., 56-C.

56 0 c.

42-C.

42 0 C.f 42-C., 9.0 100 101 126 106 9.0 100 98 101 83 9.0 100 101 102 4A

LP

100 101 109 102 102 99

I

-28- Example RT, 3M RT., 4M RT, 6M RT, 7M RT, 8M RT, 9M RT, IOM RT, 11M RT, 13M RT, 14M PRT, 16M RT, 21M PT, 24M RT, 25M RT, 27M RT, 29M RT, 30M Sun, 1M Table 10.

1A

LP

(continued) 2A

LP

100 3A

LP

4A

LP

98 99 101 82 101 101 102 102 101 .4 o 0 414 4

S

94:5 V I I S S I IS 9444 4 494w 44 44 4 4 *4 4 4 4 44 Si I I t 106 97 (a) 101 101 (a) 113 (a) 105 (a) 105 (a) 10 1 100 Gas-liquid chromatography is used for these assays and for all the assays in Example 4A. All the other assay data are derived using spect:ophotometric method of analysis. The assay results using the spectrophotometric method of analysis quite variable due to analytical interferences.

i;

I

-29- Table 11. ELECTROMETRIC pH DETERMINATIONS AT AMBIENT TEMPERATURE pH Value Example 1A 2A 3A 4A Initial 7.7 7.7 7.7 7.7 RT, 2M 6.6 RT, 4M 7.0 RT, 6M 6.8 6.6 RT, 9M 6.4 6.8 RT, 12M RT, 24M 6.7 RT, 28M RT, 29M 6.5 RT, 32M 6.4 RT, 34M 6.6 RT, 36M 6.2 The effectiveness of the preservative system 't of Leucovorin Calcium Injectable Solutions, for Comparative Examples lA, 2A, 3A, and 4A is tested in accordance with the Antimicrobial Preservatives Effectiveness Test outlined measure of the capacity of the solutions to decrease microbial growth when 0 individually challenged with Staphylococcus aureus, Escherichia coli, Psuedomonas aeruginusa, Candid albicans and Aspergillus niger at a dose level of 100,000 to 1,0,0,000 microorganisms per ml. The contaminated solutions are stored and sampled at a series of time intervals in order to obtain microorganism counts. The results of these tests are set forth in Table 12.

6 0 000 0 0* e 0 0 4 0* 9 0 *0 0 0 00 0 Table 12. Microbioloqizal Evaluatl'cn of Preservative System U.S.P. XIX Method Inoculation Count 0.5 Hour 24 Hours 1 Week 2 Weeks 4 Weeks Example 1A Staphylococcus aureus Escherichia coli Pseudomonas aeruginosa Candida albicans Aspergillus niger Example 2A Staphylococcus auraus Escherichia coli Pseudomonas aeruginosa Candida albicans Aspcrgillus niger 270,000 245,000 410 ,000 330,000 120,000 205,000 180 ,000 210,000 154 ,000 280,000 202,000 32,000 59,000 130,000 340,000 63,000 55,000 21 ,000 61,000 25 ,000 <1,000 <1,000 <1,000O <4,000 230 ,000 <1,000 <1,000 <100 48,500 270,000 <100 <100 <100 <100 57,000 <100 <100 <100 <100 29,000 <100 <100 <100 <100 1,000 <100 <100 <100 <100 1,800 <100 <100O <1l,00 <100 <100 <1I00 <100 <100 <100 <100 4 C 0 *0 0 TABLE 12 (continued) Inoculation Count 0.5 Hour 24 Hours 1 Week 2 Weeks 4 Weeks Example 3A Staphylococcus aureus 270,000 <1,000 <1,000 <100 <100 <100 Esoherichia coli 200,000 <1,000 <1,000 <100 <100 <100 Pseudomonas aeruginosa 314,000 <1,000 <1,000 <100 <100 <100 Candida albicans 78,000 <1,000 <1,000 <100 <100 <100 Aspergillus niger 210 ,000 <200 1'00 ,000 <50 <100 <100 Example 4A Staphylococcus aureus 257,000 160,000 <100 <100 <100 <100 Escherichia coli 238,000 194,000 20,000 <100 <100 <100 Pseudomonas aeruginosa 340,000 97,000 <100 <100 <100 <100 Candida albicans 114,000 92,000 <100 <100 <100 <100 Aspergillus niger 380,000 330,000 440,000 160,000 950 <100

MML-

i -32- EXAMPLES 4, 5 AND 6 Three batches are prepared with leucovorin calcium salt as the active ingredient in a composition for injection having the formula set forth in Table 13: I f I

I

i I C *44 Ca C 9 CC *~O a *0 eC a a j TABLE 13. COMPOSITON FOR INJECTION COMPRISING LEUCOVORIN CALCIUM Ingredient Leucovorin Calcium U.S.P.

Tromethamine-Reagent Grade Monothioglycerol N.F.

Sodium Chloride-Reagent Grade Hydrochloric Acid-Reagent Grade Sodium Hydroxide [iSP Water for Injection tJ.S.P.

Nitrogen Prepurified

W/V

1.100 0.150 0.200 0.560 pH 7.9-8.3 pH 7. 9-8. 3 100. 0 (v/v) Function in Composition Active Ingredient Buffer Antiox idant Tonicity Adjuster pH Adjuster pH Adjuster Vehicle Protectant** qs ad qs ad qs ad Based on Leucovojrin Anhydrous Free Acid at 100% Used as a protective gas to retard oxidation of the product during manufacture, and as a headspace gas in the final. sealed package.

I

-34- The resulting composition is a clear light yellow solution. Each batch is 40 liters. The solutions are then distributed to 50 ml amber tubing vials with 50 mg/vial label potency. Grey butyl plug closures are used with aluminum seals.

The filled dosage forms from Examples 4, -and 6 are placed on accelerated stability tests, consisting of storing the solution at 23 0 C for up to 9 months, storing the solution at 40°C and at 75% relative humidity for up to three months, and storing the solution for one month in a light cabinet.

The solutions are assayed by high performance liquid chromatography. The mean assay results of the S* tests performed on the packaged formulations of Examples 4, 5 and 6 are reported in Table 14: Table 14. Mean Assay Results For Leucovorin Calcium Injection Solutions 500 mg/vial (Examples 4, 5 and 6) Example No. 4 5 6 Storage Condition Time L.P. L.P. L.P.

Initial 110 106 109 0 23 0 C 3M 106 104 106 S 23 0 C 6M 107 105 106 23 0 C 9M 106 104 105 4 23 0 C 12M 103 102 104 0 C/75% RH 1M 102 101 101 40 0 C/75% RH 2M 99 98 100 40°C/75% RH 3M 98 97 99 LCAB* 1M 107 105 106 The packaged formulations of Examples 4, 5 and 6 did. not change in appearance after being stored at 23 0 C for up to 9 months, 40 0 C and 75% relative humidity for up to three months, and in a light cabinet for one month. The compositions remained clear light yellow solutions.

The solutions of Examples 4, 5 and 6 are measured electrometrically for pH. The results of these tests, showing that the pH remained essentially unchanged at all storage conditions, are reported in Table Table 15. pH Measurement Data For Leucovorin Calcium Injection Solutions 500 mg/vial (Examples 4, 5 and 6) Example No. 4 5 6 o 9 Storage 9o9 Condition Time pH pH pH 9 Initial 8.2 8.4 8.4 23 0 C 3M 8.1 8.2 8.3 23 0 C 6M 8.0 8.1 8.2 23 0 C 9M 8.1 8.3 8.4 23 0 C 12M 8.1 8.2 8.3 40 0 C/75% RH IM 8.2 8.4 8.4 a9 40 0 C/75% RH 2M 8.0 7.9 8.1 40 0 C/75% RH 3M 8.0 8.0 8.1 Example If the procedure of Example 1 is repeated substituting sodium folate for the calcium leucovorin, using the following ingredients: sodium folate equivalent to 5 mg of folic acid; disodium edetate Water for Injection; q.s. 100%; sodium hydroxide to approximately pH 9; benzyl alcohol; tromethamine, 0.15%; and monothioglycerol, 0.200%, all percentages by weight over volume, a stable injectable composition in accordance with this invention will be obtained.

L w -36- The foregoing data indicate that a unique blend of a buffer and an antioxidant endows leucovorin with more stability than the present standard formulation of leucovorin (Comparative Examples). More particularly, the composition of this invention is shown to be: a formulation which is more stable than the present standard product system in terms of pH: with variations of no more than 0.4 pH units from an adjusted pH of 8.1, and thus provides a stabilized alkaline pH to insure maximum stability of leucovorin calcium; a formulation with better leucovorin potency photostability after one month exposure to sunlight when 0 0" compared to the standard product formulation; a formulation which has equivalent or better 15 leucovorin potency stability overall; a formulation with equivalent benzyl alcohol potency V stability, as compared to the standard product o oo formulation.

a formulation where the generation of related compounds does not exceed the specified limits for the standard product formulation; a formulation which meets the present Antimicrobial X, Preservatives Effectiveness test as outlined in U.S.P.

0 0 0 XXI; and oo, .25 a formulation which has a projected expiration dating of at least eighteen months.

I

The above-mentioned patents, publications and test methods are incorporated herein by reference.

The foregoing detailed description will suggest many obvious variations to those skilled in this art. For example, instead of calcium leucovorin, strontium leucovorin and sodium lescovorin can be used.

Racemic and enantiomeric 1-leucovorin can be used.

-37- Benzyl alcohol can be omitted. Instead of sodium folate, calcium folate can be used. Derivatives, such as polyglutamyl folates and leucovorin can be used. The injectable compositions can contain conventional additives such as chelating agents, inert gases, and the like. All such obvious modifications are within the full intended scope of the appended Claims.

tl s il 1 1 ,I 4

Claims

1. A stable, injectable aqueous composition comprising: an effective amount of a water soluble pharmaceutically-acceptable salt of folic acid or leucovorin; (il (an effective preservative amount of benzyl alcohol; and (iii) an effective amount of a buffer/antioxidant combination comprising a o. tromethamine and "o monothioglycerol, said combination (iii) being present in an amount at least sufficient to maintain the pH of said composition in a predetermined range of from about 6 to about 10 and to protect the composition against degradation induced by oxygen or light.

2. A Jomposition as defined in Claim 1, wherein said salt comprises a salt of leucovorin. *tt

3. A composition as defined in Claim 2, wherein said leucovorin salt comprises calcium leucovorin. ,go

4. A composition as defined in Claim 2, wherein said salt comprises a salt of 1-leucovorin.

A pharmaceutical formulation comprising from 3 mg/ml to 25 mg/ml of Leucovorin Calcium in an isotonic solution at a pH of from 6.5 to 8.5, with or without benzyl alcohol at a concentration of from 0.0% w/v to 0.909% w/v, TRIS (tromethamine) at a concentration of tirm 0.10% w/v to 0.30% w/v, monothioglycerol at a concentration of from 0.10% w/v to 0.30% w/v; sodium chloride at a concentration from 0.45% to 0.65% w/v, with hydrochloric acid at a I_ 81 -39- concentration of 5.0 v/v% to 10.0 v/v% and sodium hydroxide at a concentration of 1.0 w/v% to 5.0 w/v% added as required to adjust the pH.

6. A method for stabilizing an injectable aqueous composition against deterioration, said method comprising: A. providing an aqueous composition comprising an effective amount of a water- soluble pharmaceutically acceptable salt of folic acid or leucovorin and, optionally, (ii) a small effective preservative -S amount of benzyl alcohol, and SB. adding thereto (iii) an effective amount of a buffer/antioxidant combination comprising tromethamine and a monothioglycerol, said combination being provided in an amount at least sufficient to maintain the pH of said composition in a predetermined range of from about 6 to about 10 and to protect the composition against degradation induced by oxygen and light.

7. A method as defined in Claim 6, wherein 0o oP said salt comprises a salt of lUcovorin.

8. A method as defined in Claim 6, wherein said salt comprises a salt of 1-leucovorin. ti

9. A method for stabilizing a pharmaceutical formulation comprising providing from 3 mg/ml to 25 mg/ml of Leucovorin Calcium in an insotonic solution at a pH of from 6.5 to 8.5, with or without benzyl alcohol at a concentration of from 0.0% w/v to 0.909% w/v, and adding thereto TRIS (tromethamine) at a concentration from 0.10% w/v to 0.30% w/v, monothioglycerol at a concentration of from 0.10% w/v 1 to 0.30% w/v; sodium chloride at a concentration of from 0.45% w/v to 0.65% w/v, and sufficient hydrochloric acid at a concentration of 5.0 v/v% to

10.0 v/v% and sodium hydroxide at a concentration of ,C w/v% to 5.0% w/v added as needed to adjust the pH. 10. A stable, injectable aqueous composition, substantially as hereinbefore described with reference to any one of Examples 1-5 but excluding Comparative Examples 1A, 2A, 3A and 4A.

11. A method for stabilizing an injectable aqueous composition against deterioration, substantially as hereinbefore described with reference to any one of Examples 1-5 but excluding Comparative Examples 1A, 2A, 3A and 4A. DATED this TWENTIETH day of MAY 1992 So+ American Cyanamid Company Patent Attorneys for the Applicant SPRUSON FERGUSON P i