Suppositories: Suppository bases and Question Answer for GPAT, NIPER, Pharmacist and Drug Inspector exam

Suppository bases: Analogous to the ointment bases, suppository bases play an important role in the release of the medication they hold and, therefore, in the availability of the drug.

One of the first requisites for a suppository base is that it should remain solid at room temperature but soften, melt, or dissolve readily at body temperature so that the drug is fully available soon after insertion.

Nature of the base:

• The base must be capable of melting, softening, or dissolving to release its drug for absorption.
• If the base interacts with the drug to inhibit its release, drug absorption will be impaired or even prevented.
• Also, if the base irritates the mucous membranes of the rectum, it may initiate a colonic response and prompt a bowel movement, eliminating the prospect of complete drug release and absorption.
• Because of the possibility of chemical and/
  or physical interactions between the medicinal agent and the suppository base, which
  may affect the stability and/or bioavailability of the drug, the absence of any drug
  interaction between the two agents should be
  ascertained before or during formulation.
• Long-acting or slow-release suppositories have also been prepared. Morphine sulfate in slow-release suppositories is prepared in a base that includes a material such as alginic acid, which will prolong the release of the drug over several hours.

Ideal properties of bases:

• It must retain the shape and size.
• It should melt at body temperature.
• It should be non-irritant.
• It should shrink sufficiently to remove from mould.
• It should not interfere in release or absorption of drug.
• It should permit incorporation of drug.
• It should be compatible with variety of drugs.
• It should be physically stable on storage.
• It should not be soften or harden on storage.

Classification of bases:

1. Fatty or Oily Bases or Oleaginous bases
2. Water Soluble & Water miscible bases Or Hydrophilic bases
3. Emulsifying/Synthetic bases

1.Fatty or Oily Bases or Oleaginous bases: Fatty bases are perhaps the most frequently employed suppository bases, principally because cocoa butter is a member of this group of substances.

Examples – Cocoa butter or Theobroma Oil, Emulsified cocoa butter, Hydrogenated oils

Cocoa butter or Theobroma Oil – Cocoa butter is fat obtained from the roasted seed of Theobroma cocoa. At room temperature it is a yellowish, white solid having a faint, agreeable chocolate like odour. Chemically, it is a triglyceride (combination of glycerin and one or different fatty acids) primarily of oleopalmitostearin and oleodistearine. It melts at 30 – 350C.

Advantages:

• Melting just below the body temperature.
• Maintaining its solidity at usual room temperatures.
• Readily liquefy on heating and solidify on cooling.

Disadvantages:

• Stick to mould
• Leakage from body cavity
• Immiscibility with body fluid.
• Chloral hydrate or lactic acid liquefy it.

Emulsified cocoa butter – Emulsified theobroma oil may be used as a base when large quantities of aqueous solutions are to be incorporated. 5% glyceryl monostearate, 10% lanette wax, 2-3% cetyl alcohol & 4% bees wax is recommended for emulsified theobroma oil.

Hydrogenated oils – Hydrogenated oils are used as a substitute of theobroma oil. E.g. Hydrogenated edible oil, coconut oil, hydrogenated pea oil, stearic acids, palm kernel oil etc.

Advantages:

• Overheating does not affect the solidifying point.
• They are resistant to oxidation.
• Lubrication of the mould is not required.
• Their emulsifying & water absorbing capacity are good.

Disadvantages:

• On rapid cooling they become brittle.
• When melted they are more fluid than theobroma oil & result in greater sedimentaion of the added substance.

2.Water Soluble & Water miscible bases Or Hydrophilic bases: The main members of this group are glycerinated gelatin and polyethylene glycols.

Examples – Glycero-gelatin base, Polyethylene glycol

Glycero-gelatin base – It is a mixture of glycerin and water which is made stiff by the addition of gelatin. Properties: It is colourless, transparent, translucent in nature. It is soft to touch. It melts at 30 – 350C. Used for vaginal suppositories.

Advantages:

• It melt at body temperature.
• It mix with body fluid.
• Not rancid
• It can be used to prepare suppositories using boric acid, chloral hydrate bromides, iodides, iodoform opium etc.

Disadvantages:

• Difficult to prepare and handle.
• Chance of bacterial growth.
• Hygroscopic in nature (become hard on drying and soft in cont with moisture)
• Laxative in action. ◦ Incompatible with tannic acid, ferric chloride etc.

Polyethylene glycol/Macrogols – These are commonly known as carbowaxes & Polyglycols. These are available in solid, liquid or semi- solid state depending on molecular weight. Those polymers having the molecular weight betw. 200 to 1000 are liquids & those having M.W higher than 1000 are wax like solids. They are chemically stable & physiologically inert substances & do not allow the bacterial or mold growth to take place.

Advantages:

• They are chemically stable.
• Inert, Non-irritant.
• Do not allow bacterial growth.
• Physical properties changes according to molecular weight.
• Provide prolonged action.
• Do not stick to mould.
• Suppositories are clean and smooth in appearance.

3.Emulsifying/Synthetic bases:

Examples – Witepsol , Massa estarinum

Witepsol – They consist of triglycerides of saturated vegetable fatty acid with varying percentage of partial esters. A small amount of beeswax is added for use in hot climate. It should not be cooled rapidly as it become brittle and fracture. Lubrication is required.

Massa estarinum – It is a mixture of mono, di and triglycerides of saturated fatty acids. It is a white, brittle, almost odourless and tasteless solid.  It has a m.p. 33.5 to 35.50C. They are available in various grades but grade B is commonly used in dispensing.

Advantages of Emulsifying/Synthetic bases:

• They solidify rapidly.
• They are non-irritant.
• The lubrication of mould is not required.
• Overheating does not affect the physical properties of the base.
• They can absorb fairly large amount of water or aqueous liquids.
• The white, odourless, clean and attractive suppositories are produced.
• They are less liable to get rancid.

Disadvantages of Emulsifying/Synthetic bases:

• They should not be cooled rapidly in a refrigerator because they become brittle.
• They are not very viscous on melting, so the medicaments incorporated with the base settle down rapidly.

Multiple choice questions:

1.Suppository base is that it should remain ____ at room temperature.

a)solid

b)liquid

c)gaseous

d)semi solid

2..Suppository base should _____ at body temperature.

a)soften

b)melt

c)dissolve

d)all of these

3.The base must be capable of _____ to release its drug for absorption.

a)softening

b)melting

c)dissolving

d)all of these

4.If the base interacts with the drug to inhibit its release, drug absorption will be impaired or even prevented.

a)true

b)false

5.Slow-release suppositories contain

a)alginic acid

b)acetic acid

c)citric acid

d)all of these

6.Which of the following is not an ideal property of bases?

a)It must retain the shape and size

b)It should shrink sufficiently to remove from mould

c)It should be compatible with variety of drugs

d)It should soften or harden on storage

7.Suppository bases are classified as

a)Fatty or Oily Bases or Oleaginous bases

b)Water Soluble & Water miscible bases Or Hydrophilic bases

c)Emulsifying/Synthetic bases

d)All of these

8.Which of the following is/are Oleaginous bases?

a)Theobroma Oil

b)Glycero-gelatin base

c)Massa estarinum

d)All of these

9.Cocoa butter is fat obtained from

a)stem of Theobroma cocoa

b)roasted seed of Theobroma cocoa

c)roasted leaves of Theobroma cocoa

d)all of these

10.Cocoa butter melts at

a)20 – 25 degrees

b)30 – 35 degrees

c)above 40 degrees

d)below 20 degrees

11.Disadvantages of Cocoa butter is/are

a)Rancidity

b)Stick to mould

c)Costly

d)All of these

12.Which of the following are Hydrogenated oils?

a)coconut oil

b)stearic acids

c)palm kernel oil

d)all of these

13.Polyethylene glycol is which type of suppository base?

a)Fatty or Oily Bases or Oleaginous bases

b)Water Soluble & Water miscible bases Or Hydrophilic bases

c)Emulsifying/Synthetic bases

d)All of these

14.Polyethylene glycol is also known as

a)Witepsol

b)Massa estarinum

c)Macrogol

d)All of these

15.Witepsol is classified as which type of suppository base?

a)Fatty or Oily Bases or Oleaginous bases

b)Water Soluble & Water miscible bases Or Hydrophilic bases

c)Emulsifying/Synthetic bases

d)All of these

Solutions:

1. a)solid
2. d)all of these
3. d)all of these
4. a)true
5. a)alginic acid
6. d)It should soften or harden on storage
7. d)All of these
8. a)Theobroma Oil
9. b)roasted seed of Theobroma cocoa
10. b)30 – 35 degrees
11. d)All of these
12. d)all of these
13. b)Water Soluble & Water miscible bases Or Hydrophilic bases
14. c)Macrogol
15. c)Emulsifying/Synthetic bases

References:

1. Ansel’s Pharmaceutical Dosage Form and Drug Delivery System, 10th edition, page no. 371-374.

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