The various evaluation tests for suppositories

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

Test of appearance

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.

Test of physical strength

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.

PROCEDURE

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.

Test of dissolution rate

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.

METHOD

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.

Reference:

L. Lachman, H.A, Lieberman and J.L. Kanig, Theory & Practice
of industrial pharmacy, Lea & Febieger, Philadelphia Latest Edn

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