Water Soluble or Water Miscible Base for suppositories

(i) Glycero Gelatin 

It is a mixture of glycerin and water which is made into a stiff jelly by the addition of gelatin. The proportion of gelatin can be varied according to the intended use of the preparation. 

Gelato-glycerin bases dissolve in the body fluids liberating contained medicaments  Gelato-glycerin Mass BP contains 14% gelatin, 70% glycerin, and water. USP formula contains 20% gelatin together with 70% of glycerin. 

For dispensing purposes, good-quality powdered gelatin should be used. To control the consistency, glycerin can be partially or wholly substituted by propylene glycol and polyethylene glycol. The incompatibility of some medicaments can be avoided by the use of either Pharmagel A (cationic) or Pharmagel B (anionic). Glycerin suppositories are liable to mold growth, and preservatives should be added. 


(a) Physiological effect: osmosis occurs during the dissolving of the mucous secretions of the rectum, producing a laxative effect. 

(b) It can cause rectal irritation due to a small amount of liquid present. 

(c) Unpredictable solution time.

(d) Hygroscopic: So, they should be packaged in tight containers and also have dehydrating effects on the rectal and vaginal mucosa leading to irritation. 

(e) Microbial contamination likely. 

(f) Long preparation time. 

(g) Lubrication of the mold is essential. 

(ii) Soap Glycerin 

In this case, soap is employed instead of glycerin for hardening. Sodium stearate can incorporate up to 95% of glycerin. Sodium stearate (soap) is produced in situ by the interaction of sodium carbonate with stearic acid. Soap glycerin suppositories are however hygroscopic. 

(iii) PEG Bases 

Different mixtures of polyethylene glycols are marketed under the trade names of  Postonals, Carbo waxes, and Macrogols. 

Most of the drugs commonly administered in suppository form are compatible with these bases. Polyethylene glycols are however incompatible with phenols and reduce the antiseptic effects of quaternary ammonium compounds.

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