Give the list of different types of suppository bases. List out the various qualities or ideal properties of suppository base. Describe any two types of bases used for the preparation of suppositories

 

Suppositories: A semisolid substance for introduction  into the rectum, vagina, or urethra, where it dissolves. it may be used to stimulate a bowel movement, but often serves as a vehicle for medicines to be absorbed. It commonly shaped like a cylinder or cone and may be made of soap, glycerinated gelatin, or cocoa butter(oil of Theobroma).

Ideal properties of suppository bases:

• It should melt at body temperature or dissolve or disintegrate in body fluids.
• Higher melting point bases may be necessary for eutectic mixtures. Addition of balsams to suppositories is intended for use in tropical climates.
• It should be inert, no-irritating and non-sensitizing
• It should be release the medicament readily.
• It should be compatible with a broad variety of drugs.
• It should be stable on storage and transportation.
• It should have wetting and emulsifying properties.
• It should be able to incorporate a high percentage of water in it i.e., a high water number.
• It should shrink sufficiently on cooling to release itself from mold and should be moldable by pouring or by cold compression.
• Fatty bases should have acid value below 0.2, saponification value in between 200to 245, iodine value   less than 7 and a small range between the melting the melting and solidification points.

Suppository bases can be classified into three categories:

1. Fatty bases(oleagenious bases)
2. Water soluble or miscible bases
3. Emulsifying bases.

  1. Fatty bases: 

• Theobroma oil: It is yellowish white solid obtained from crushed and roasted seeds of Theobroma cocoa.
• It is also known as cocoa butter with melting point of 30-35 C
• It is a mixture of glyceryl esters of stearic acid, oleic acid. It melts at body temperature and release the medicament for rapid absorption 
• It readily liquefies on warming and quickly settles on cooling.

    Disadvantages

• It shows polymorphism.
• It become rancid and melts in warm weather.
• It has a tendency to stick to the sides of mould when solidified.
• Leakage from body cavities on melting takes place.
• Relatively costly.
• Immiscible with body fluids.

    Emulsified Theobroma oil:

• Used as a base when large quantity of aqueous solutions are to be incorporated.
• 5% glyceryl monostearate, 10% lenette wax, 2-3% cetyl alcohol, 4% bees wax and 12% spermaceti is recommended in the preparation of emulsified theobroma oil suppositories.

    Hydrogenated oils:

• They are obtained by hydrogenation of various vegetable oils such as arachis oil, cotton                   seed oil etc.
• It is used as a substitute for theobroma oil because it has many advantages as.
• Resistant to oxidation.
• Lubrication of mould.
• Overheating doesn't affect the solidifying point.
• Colorless, odorless and elegant suppositories are formed.
• Emulsifying and water absorbing capacities are good.

2. Water miscible and water soluble bases:

    a)Glycerogelatin base:

• It is a mixture of glycerin and water which is made stiff by adding gelatin.
• The suppositories prepared by this are translucent, dissolve or disperse slowy in the body cavity and release the medicament.
• To avoid incompatible reactions Type A which is acidic in nature are used for acidic drugs having iso-electric point(7-9).
• Type-B which is alkaline in nature and used for alkaline drugs having iso-electric point(4.7-5)

    Disadvantages:

• Gelatin is incompatible with many drugs.
• There are more chances of bacterial growth.
• Solution time depends on the content and quality of gelatin used.
• They are more difficult to prepare and handle.

    b)Polyethylene glycol:

• They are called as carbowaxes or polyglycols or macrogals.
• They have molecular weight less than 1000 are liquids and more than 1000 are wax like solids.

    Advantages:

• Chemically active .
• Non irritant.
• No bacterial growth.
• Inert substances.
• Have clean and smooth appearance.

    Disadvantages:

• Hygroscopic.
• Incompatible with tannins, phenols etc.
• Supersaturation and forms crystals and fracture on storage.

3.Emulsifying bases:

    a)Witepsol:

• Consist of triglycerides of saturated vegetable acid with various percentage of partial esters.
• Bees wax is added in hot climates.
• Suppositories should not be cooled rapidly to prevent from brittle and fractures.

    b)Massa estarnium:

• Mixture of mono, di and triglycerides of saturated fatty acids.
• They are also called as a deps solidus.

   c) Massuppol:

• It consist of glycerol esters of lauric acid to which small amount of glyceryl monostearate has been added to improve it water absorbing capacity.

    Advantages:

• Solidify rapidly.
• Non irritant.
• Lubrication of mould is not required.
• Over heating has no effect on base.
• Absorb huge amount of water.

    Disadvantages:

• Should not be could rapidly.
• Not very vicious on melting.