The various evaluation tests for suppositories are
- Test of appearance
- Test of physical strength
- Test of dissolution rate
- Test of melting range
- Test of softening time
- Test of uniformity of drug content
- Test of drug uptake
All the suppositories should be uniform in size and shape. They should have elegant appearance. Individual suppositories should be examined for cracks and pits due to entrapment of air in the molten mass.
In this test, tensile strength of suppositories is measured to assess their ability to withstand the rigors of normal handling.
The apparatus used is called as breaking test apparatus. It consists of a double-wall chamber. Through the walls of the chamber, water is pumped. The inner chamber consist of a disc which holds the suppositories. To this disc, a rod is attached. The other end of the rod consists of another disc on which weights are placed.
On the first disc the test suppository is placed. On the second disc a 600 g weight is placed. At 1 minute interval, 200 g weights are added till the suppository crumbles. All the weights used are added which gives the tensile strength. Likewise, few more suppositories are tested and the average tensile strength is calculated. Tensile strength indicates the maximum force which the suppository can withstand during production, packing and handling. Large tensile strength indicates less tendency to fracture.
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.
Two types of apparatus are available for testing the dissolution rate. They are:
(a) Suppository dialysis cell - Lipophilic suppositories are tested using suppository dialysis cell, which is also called as modified flow-through cell.
(b) Stationary basket - Rotating paddle apparatus ( USP dissolution test apparatus ). Hydrophilic suppositories are tested using stationary basket - rotating paddle apparatus.
Test of melting range
Both macromelting range and micromelting range are determined.
(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.
Test of softening time
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.
The apparatus consists of a cellophane tube tied at the two ends of a condenser. The two ends of the cellophane tube are open. Water is circulated through the condenser at a definite rate. As a result, after some time the upper half of the tube opens wide and the lower half collapses. A suppository is dropped into the water in the condenser. The time period in which the suppository melts completely is noted as the softening time.
Test of uniformity of drug content
This test is to assess the uniformity of the mixed suppository mass. Different suppositories are assayed for the drug. All the suppositories should contain the same labelled quantity of the drug.
Test of drug uptake
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. 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 in 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.
L. Lachman, H.A, Lieberman and J.L. Kanig, Theory & Practice
of industrial pharmacy, Lea & Febieger, Philadelphia Latest Edn
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