(1) Effect of excessive heat. Cocoa butter has a crystalline structure which
breaks down when overheated. If suppositories are made from overheated cocoa
butter, they will liquefy at approximately 23-24C (75 F) rather than the desired higher
temperature of 30C (94F). Therefore, when making suppositories of theobroma oil,
always be careful to use only enough heat to liquefy the material, NEVER enough to
destroy the natural crystalline structure.
(2) Raised or lowered melting point. When substances such as chloral
hydrate and liquefied phenol are added to theobroma oil, they cause the melting point of
the finished suppository to be greatly lowered. They may become soft or even liquid at
room temperature. In addition, unusually warm or cold climates make the melting point
of cocoa butter suppositories unsatisfactory.
b. Glycerinated Gelatin. There are many different formulas for this substance.
They involve varying amounts of glycerin, gelatin, and water. The following formula for
making pure or medicated glycerinated gelatin suppositories has been recommended.
Medicinal substance (prescribed quantity)
Purified water, a sufficient quantity to make .. ... 10 g
Gelatin, granular .......................................... 20 g
Glycerin ............................................................ 70 g
Unlike cocoa butter suppositories, glycerinated gelatin suppositories do not melt at body
temperature. Instead, they dissolve in body secretions or in contents of the cavity into
which they are introduced. The time necessary for solution varies, depending upon the
ratio of the ingredients, and the presence of peptizing agents or chemicals.
c. Polyethylene Glycols. These substances are solid at room temperature and
very soluble in water. Suppositories made with polyethylene glycol bases must be
prepared by the fusion method. They are popularly called Carbowaxes and the
increasing solidity is identified by an increasing number in the name. Carbowax 300 is
a viscid liquid; Carbowax 1540 is a solid. The Carbowaxes are becoming ever more
popular as suppository bases and are excellent for water-soluble medicaments. Other
water miscible formulations are surface active derivatives of polyethylene glycol and
they are nonionic. An example is polyethylene glycol sorbitan monopalmitate (Tween
61).
MD0809
5-10