Other Fatty Media

The late W. Martindale spoke highly of a mixture of equal parts of stearic and oleic acids as a substitute for cocoa-butter; the advantages which he claimed for it are that(1) The mixture has a very low fusing-point, and readily melts at the temperature of the body.

(2) The suppositories leave the mould without difficulty.

(3) It has the advantage, besides being a solvent of such alkaloids as pure morphine, atropine, cocaine, etc, of being, at least as far as the oleic acid is concerned, readily absorbed by the skin and mucous membrane.

(4) On account of the partial crystallisation of some of the stearic acid, the suppositories are firm, and can be placed in their position withou difficulty, not being elastic, brittle, or yielding in any way.

(5) The proportions of stearic and oleic acids can be varied to suit the temperature of summer or winter, and also the other ingredients prescribed with them.

These opinions were expressed many years ago, but cocoa-butter has maintained its pre-eminence, which it deserves. It is very uniform, bland, keeps well, and has an agreeable odour. The others vary in melting-point and require to be watched in this respect; they incline also to develop a peculiar odour without much provocation: they are most suitable for use on the large scale by experts, and they work out rightly on the score of economy. Coco-nut stearin is better than ordinary stearin or than Mr. Martindale's mixture. It was long ago recommended by Dr. Bowman Brady, and Squire speaks well of it. Mr. C. J. S. Thompson finds a mixture of 4 ounces of the stearin and 340 grains of white wax suitable. A mixture of anhydrous wool-fat (3 parts) and hard paraffin (1 part) is excellent for fluids and extracts. For extracts and liquids Lucas recommends cocoa-butter 99 and anhydrous wool-fat 1.

The Gelatin Basis

Although sometimes employed in making pessaries, this basis is generally considered to be not nice for these, as the gelatin mats the pubic hairs, and the only advantage which the basis possesses over cocoa-butter is the contained glycerin- frequently a valuable therapeutic agent in uterine troubles. The basis is much used for nasal bougies. The following are recommended formulae:

Soak the gelatin in the water for twelve hours, add the glycerin, dissolve on a water-bath, and evaporate until the mass weighs 15 oz.

Soak the gelatin in the water until absorbed, add the glycerin, and dissolve by the heat of a water-bath.

The B.P. formula for suppos. glycerin, is substantially Squire's, but the directions are not so good as Squire's. The finest French gelatin, in thin, almost colourless sheets, should be used. One mass is not universally applicable, medicaments acting upon it in diverse ways. Ochse gives the following hints as to the use of gelatin bases:

Where gelatin suppositories are frequently dispensed it is best to have a definite mass in stock. This is made in large or small quantities, according to the requirements of the pharmacist. After removing the scum from the solution the latter is poured into bottles, and when thoroughly cooled covered with alcohol to prevent it from becoming mouldy. When wanted for use the alcohol is drained off, the bottle placed in a water-bath, and the required quantity poured off. The mass is made as follows: The accurately weighed gelatin is allowed to macerate overnight in distilled water, and drained on a sieve. The gelatin adhering to the sieve is collected, the whole placed in a tared porcelain dish, and sufficient water added to make the weight four or five times as much as the original quantity of gelatin used. The dish is placed, on the upper ring of a retort-stand and heated over wire gauze with a gas or spirit-lamp flame, care being taken not to burn the gelatin. The glycerin is added (in all the subjoined formulae the parts are to be by weight) and the whole evaporated to the consistency required, viz.:

I. Gelatin 20 parts, water 80 parts, glycerin 40 parts; evaporated to 60 parts. Intended for preparations kept in stock and for those which are to retain their transparency.

II. Gelatin 10 parts, water 40 parts, glycerin 15 parts; evaporated to 25 parts. For hygroscopic drugs, for bougies of perchloride of iron (made by dissolving 1 part of ferric chloride in 9 parts of water, and adding to 19 parts of the mass), for tannin suppositories (0.2 per cent- but this recommendation is opposed to theory), and for vaginal pessaries containing iodide or bromide of potassium, bromide, chloride, or salicylate of sodium, and ergotin. Chloral-hydrate suppositories are made with this mass, the hydrate being dissolved in as little water as possible.

III. Gelatin 10 parts, water 40 parts, glycerin 20 parts; evaporated to 50 parts. For suppositories generally, also in special cases, as for carbolic acid (and similar medicaments soluble in a small quantity of alcohol), which are made by adding 3 parts of carbolic acid, previously dissolved in alcohol, to 7 parts of glycerin and 50 parts of this mass. To make alum bougies, liquefy 25 parts of the mass and 10 parts of distilled water on a water-bath. To this add a hot solution of 7 parts alum, 10 parts glycerin, and 5 parts distilled water. The whole is then evaporated with gentle stirring to 35 parts. The mixture becomes thick and turbid on adding the solution of alum, but, on heating over a water-bath and stirring carefully, it soon becomes clear and transparent.

IV. Gelatin 10 parts, water 40 parts, glycerin 30 parts; evaporated to 60 parts. This mass is used for certain vaginal pessaries, and for urethral bougies, especially those containing sulphate of zinc, sulphate of copper, nitrate of silver, extract of opium, hydrochloride of morphine, and bichloride of mercury. One part of any of them is dissolved in a little water, and then added to 99 parts of mass and poured into moulds. If it is desired to make a large quantity of sulphate of copper bougies, it is best to mix not more than the mould will hold at a time, because by frequently heating the mass the bougies acquire a yellowish-green instead of a blue-green colour.

V. Gelatin 30 parts, water 120 parts, glycerin 15 parts; evaporated to 104 parts. Used for bougies containing a large percentage of powdered drugs insoluble in water or alcohol. Thus 50-per-cent. bougies of iodoform are made by adding 27 parts of powdered iodoform to 54 parts of mass. When taken from the mould the bougies are placed in a drying-closet until they weigh about two-thirds of their original weight.

The quantities of medicaments indicated may, of course, be modified. Those given serve to show how the active ingredients are added.

In making suppositories with the gelatin basis, the mould should be cold, clean, and quite dry; then thinly coated inside with almond oil. When turned out the suppositories should be wiped with a dry cloth in order to remove the oil, or placed for this purpose on a sheet of filtering-paper. A mortar or slab is not convenient to use with this basis, which is simply melted in a dish, and the medicament stirred in until thoroughly dissolved or diffused. The gelatin basis is well adapted for the exhibition of alkaloids and aqueous extracts, but not for tannin, carbolic acid, or bromide and iodide of potassium.