• Substances that can be used to make suppositories are referred to as suppository bases.
• Bases are used to hold the medicament & release the drug after administration.
• Base has not pharmacological action.
• Example- Theobroma oil (cocoa butter) , glycerolelatin base & PEG (Polyethylene glycol) etc.

Properties of ideal suppository base:-

• It should Nontoxic, non-allergenic and nonirritating to mucous membranes.
• It should Compatible with a variety of drugs.
• The base melts or dissolves in rectal fluids/body cavities.
• It should release the medicaments readily
• The base should be stable on storage
• It should not bind or otherwise interfere with the release or absorption of drug substances.
• It should be stable if heated above its melting point.
• It should be molded easily and should not adhere to the mold.

Commonly used suppository bases are:

1. Cocoa butter & cocoa butter substitutes (primarily vegetable oils modified by esterification, hydrogenation and/or fractionation),
2. Glycerinated gelatin,
3. Hydrogenated vegetable oils,
4. Mixtures of polyethylene glycols of various molecular weights, and
5. Fatty acid esters of polyethylene glycol.

Types of Suppository base

1. Fatty suppository bases

i) Cocoa Butter or Theobroma Oil:

• It is a yellowish-white solid having chocolate flavor. It is a mixture of glyceryl esters of stearic, palmitic, oleic and other fatty acids.
• There are mainly four types of homogeneous cocoa butter is used as base. There are four distinct crystal forms of α, β, β,’and γ.
• Among them, the three crystal forms of α, β,’and γ are unstable, the melting point is low, and the β type is stable.
• Melting point of theobroma oil- 30-35 °C.
• Solidification temp.- 12-13 °C.
• Iodine value of Cocoa butter- 34-38.
• Acid value of theobroma oil->4
• Most stable form- β- form of cocoa butter.

• Advantages:
  • A melting point range of 30 to 36 ⁰C; hence it is solid at normal room temperatures but melts in the body.
  • Ready liquefaction on warming and rapid setting on cooling.
  • Miscibility with many ingredients.
  • Blandness i.e. does not produce irritation.
• Disadvantages
  • Polymorphism
  • Adherence to mould
  • Softening point too low for hot climates
  • Melting point reduced by soluble ingredients
  • Slow deterioration during storage
  • Poor water absorbing capacity
  • Relatively high cost

ii) Semi-synthetic or synthetic fatty acid glycerides:

As a substitute of theobroma oil, a number of hydrogenated oils, e.g. hydrogenated edible oil, arachis oil, coconut oil, palm kernel oil, stearic and a mixture of oleic and stearic acids are used as a base.

Advantages of these synthetic fats over theobroma oil:-

• Their solidifying points are unaffected by overheating.
• They have good resistance to oxidation because their unsaturated fatty acids have been reduced.
• Their emulsifying and water absorbing capacities are good. [They usually contain a proportion of partial glycerides some of which, e.g. glyceryl monostearate, are w/o emulsifying agents and, therefore, their emulsifying and water absorbing capacity are good.
• No mould lubricant is required because they contract significantly on cooling
• They produce colorless, odourless and elegant suppositories

Disadvantages

• They should not be cooled in refrigerator because they become brittle if cooled quickly. Certain additives e.g. 0.05 % polysorbate80, help to correct this fault.
• They are more fluid than theobroma oil when melted and at this stage sedimentation rate is greater. Thickeners such as magnesium stearate , bentonite and colloidal silicon dioxide, may be added to reduce this.

2. Hydrophilic suppository base

Water soluble/water miscible bases are those containing glycerinated gelatin or the polyethylene glycol (PEG) polymers.

Hydrophilic (Water-loving base) suppository base includes two categories.

• A. Water soluble Bases
• B. Emulsifying Bases

A. Water-soluble Bases:

Water-soluble base favors more drug release from suppository than Fatty/oil base. Example

i) Glycero Gelatin bases:-

• These bases are a mixture of glycerol and water made into a stiff jelly by adding gelatin (mixture of Gelatin + glycerine + water).
• It is used for the preparation of jellies, suppositories and pessaries. The stiffness of the mass depends upon the proportion of gelatin used which is adjusted according to its use.
• The base being hydrophilic in nature, slowly dissolves in the aqueous secretions and provide a slow continuous release of medicament.
• Glycerogelatin base is well suited for suppositories containing belladonna extract, boric acid, chloral hydrate, bromides, iodides, iodoform, opium, etc.
• Depending upon the compatibility of the drugs used a suitable type of gelatin is selected for the purpose. Two types of gelatins are used as suppository base.

B. Emulsifying Bases (Water Miscible):–

• These are synthetic bases Synthetic bases.

Example

1. Witepsol
2. Massa estarinum
3. Massupol

1. Witepsol

They consist of triglycerides of saturated vegetable acids (chain length C12 to C18) with varying proportions of partial
esters.

2. Massa Esterium

This is another range of bases, consisting of a mixture of di-, tri- and mono- glycerides of saturated fatty acids with
chain lengths of C11 to C17.

3. Massuppol

It consists of glyceryl esters mainly of lauric acid, to which a small amount of glyceryl monostearate has been added to
improve its water absorbing capacity

Types of Suppository base pdf

Also Read…

Liquefaction testing provides information on the behavior of a suppository when subjected to a maximum temperature of 37◦C. The test commonly used is Krowczynski’s method, which measures the time required for a suppository to liquefy under pressures similar to those found in the rectum (approximately 30 g) in the presence of water at 37◦C. In general, liquefaction should take no longer than about 30 minutes.