OINTMENTS:- Ointments are homogeneous, semi-solid preparations intended for external application to the skin or mucous membranes. They are used as emollients or for the application of active ingredients to the skin for protective, therapeutic, or prophylactic purposes and where a degree of occlusion is desired .
CREAMS:- Creams are homogeneous, semi-solid preparations consisting of opaque emulsion systems. Their consistency and rheological properties depend on the type of emulsion, either water-in-oil (w/o) or oil-in-water (o/w), and on the nature of the solids in the internal phase. Creams are intended for application to the skin or certain mucous membranes for protective, therapeutic, or prophylactic purposes, especially where an occlusive effect is not necessary. The term “cream” is most frequently used to describe soft, cosmetically acceptable types of preparations.
QC TESTS FOR OINTMENTS AND CREAMS:-

1. Physical appearance:- Following characteristics must be evaluated for physical appearance of ointments and creams;

• Cracking of emulsion (separation of oil and water phase)
• Development of granular or lumpy appearance
• Marked changes in viscosity
• Crystal growth
• Gross microbial contamination

2. Particle size determination:- Dilute suitable amount of the preparation with equal amount of glycerol or liquid paraffin (as specified in monograph). Mount the mixture on the slide and examine under high resolving power microscope. Count the number of particles with diameter above or below than the specified limit in the monograph. Compare the percentage with the official limits.
3. Weight Variation Test:- Select the 10 filled containers. Remove any label that could lead to weight variation. Cleanse the outer thoroughly, dry and weigh each unit individually. Cut the lateral part of containers, remove their contents by washing, dry them and weigh each unit along with its corresponding parts. Difference between the weights gives the weight of the content. Calculate the average weight of the contents.

SPECIFICATIONS:- The average net weight of the content should not be less than the labelled amount. The net weight of the contents of any single container should not be less than 90% of the labelled amount (for 60g or less) and not less than 95% of the labelled amount (for more than 60g but not more than 150g). If the requirements are not met, weigh the contents of 20 additional containers. Average net weight of the contents of 30 containers must not be less than the labelled amount. Contents of not more than 1 out of 30 containers should be less than 90% of the labelled amount (for 60g or less) and not less than 95% of the labelled amount (for more than 60g but not more than 150g).

4. Solubility test:- The contents should be soluble in 9 parts of water and in 1.7 parts of hot water. The contents should be miscible with alcohol, ether and chloroform.
5. Viscosity determination:- Viscosity shall be determined as specified in the individual monograph.
6. Assay of active contents:- Assay of active contents should be performed according to official monograph and percentage should be within the official limits.
7. Sterility test for ophthalmic ointments:- This shall be performed according to the official monograph by any of the following method specified:-

• Membrane filtration method
• Direct inoculation method

8. Metal Particles in Ophthalmic Ointments:- Melt the contents of 10 tubes individually/separately in 60mm Petri dishes. Cover the dishes and heat at 85 ° C for 2hours; if needed, slightly increase the temperature to achieve full fluidity. Allow each to cool at room temperature and solidify. Invert the Petri dish on the stage of microscope furnishing 30times magnification and equipped with calibrated eye piece micrometer. In addition to usual light source, direct an illuminator from the above at an angle of 45 °. Examine the bottom of the entire Petri dish for metal particles.

SPECIFICATIONS:- Count the particles greater than 50µm in any dimension. Not more than one tube should contain 8 such particles and total number of such particles in all 10 tubes should not exceed 50. If the requirements are not met, perform the test on 20 additional containers. Not more than 3 out of 30 tubes should contain more than 8 particles and the total number of such particles in all 30 tubes should not exceed 150.
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Reference links
https://www.slideshare.net/mobile/hussain_761/qc-tests-of-ointments
http://thepharmacistpharma.blogspot.in/2009/03/evaluation-of-ointments.html?m=1