Evaluation of Pharmaceutical Suppositories

TESTS FOR SUPPOSITORIES

1. Uniformity of weight
2. Disintegration test
3. Content uniformity test
4. Melting point determination test
5. Liquefaction time (softening)
6. General appearance test
7. Assay of active contents
8. Test of drug uptake/ absorption in to blood steam

1. UNIFORMITY OF WEIGHT

• Weigh 20 suppositories individually.
• Determine their average weight.
• Not more than two of individual weights should deviate from the average weight more than 5% and none deviates by more than 10%.

2. DISINTEGRATION TEST

It is the amount of dosage form that gets dissolved in body fluid in unit time. It is a measure of the rate of drug release from the suppository.

(a) Suppository dialysis cell:

Lipophilic suppositories are tested using a suppository dialysis cell, which is also called a modified flow-through cell.

(b) Stationary basket: 

Rotating paddle apparatus (USP dissolution test apparatus). Hydrophilic suppositories are tested using a stationary basket rotating paddle apparatus.

Disintegration is complete when molded suppositories are:

• Completely dissolved.
• Dispersed into its components.
• Have become soft.

Disintegration occurs in not more than 30 minutes for fat based suppositories and for water-soluble suppositories disintegration occurs in not more than 60 minutes.

3. CONTENT UNIFORMITY TEST

• Take 10 suppositories; determine the active ingredients of each of the 10 suppositories by using a suitable analytical method.
• If not more than one of the individual values thus obtained is outside the limit i.e.% of the average value and none of them is outside the limit i.e. 25% of the average value.
• Repeat the test by using another 20 suppositories taken at random. If out of 30 suppositories not more than 3 individual values are outside the limit 15% of the average values and none is outside the limit 25% of the average value, then the test is O.K, otherwise failed.

4. MELTING POINT DETERMINATION TEST

Both micro melting range and micro melting range are determined as follows:

(a) Macromelting range

It is a measure of the thermal stability of the suppository. It is the time taken by the entire suppository to melt in a constant temperature water bath. The test is conducted using the tablet disintegration apparatus. The suppository is immersed in a constant water bath. Finally, the melting range is recorded.

(b) Micromelting range

The melting range of the fatty base is measured in capillary tubes.

5. Liquefaction time (softening)

Softening time is the time for which the suppository melts completely at a definite temperature. This test measures the softening time of suppositories which indicates the hardness of the base.

A liquefaction temperature/time test was done using the fabricated instrument. A big pipette was taken having a narrow opening on one side and a broad opening on another side. The pipette was dipped in hot water maintained at 35 ± 0.2°C so that the narrow end faces towards hot water. The sample suppository was introduced from the top of the pipette through the broad end and carefully pushed down its length until it reaches the narrow end. A glass rod was then inserted so that it rests over the suppository. The temperature at which the glass rods just come down was noted, which represents the liquefaction temperature. The time at which the glass rod reaches to narrow end after complete melting of suppositories represents the liquefaction time.

6. GENERAL APPERANCE

All the suppositories should be uniform in size and shape. They should have an elegant appearance. Individual suppositories should be examined for cracks and pits due to the entrapment of air in the molten mass.

7. Assay of active content

Official limit for the active contents is 95- 105%

8. Test of drug uptake/ absorption in to blood steam

Both in-vitro and in-vivo tests should be conducted to assess the amount of drug absorbed into the systemic circulation.

(a) In-Vitro test

The test conditions should be similar to those inside the human body. The dissolution apparatus is used which consists of simulated gastric and simulated intestinal fluids. A definite number of suppositories are placed in the apparatus. Aliquot portions of the dissolution medium are withdrawn at definite intervals of time and drug uptake is measured using a U.V. spectrophotometer.

(b) In-Vivo test

This test is carried on animals or human volunteers. The suppository is placed in the intended body cavity. At regular intervals of time, blood samples are collected and the amount of drug present is determined.

Stability Problems of Suppositories:

a. Blooming

During storage cocoa butter suppositories sometimes show deposition of white powder on the surface. This results in suppositories of disagreeable appearance.

b. Hardening

During storage, the suppositories made of fatty bases become hard. Hardening is occurred due to the crystallization of bases. This also affects the melting and rate of absorption of drugs.

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