The Pharmaceutics and Compounding Laboratory

Quality Control

Section <795> of the USP 24/NF19 Supplement 1 requires that the capsule, "shall not be less than 90% and not more than 110% of the theoretically calculated weight of each unit." This "weight variation" requirement (discussed in Section <905> of the USP 24/NF19) measures the variability in the amount of powder contained in each capsule. This procedure can be carried out in all pharmacies.

The other Dosage Form Uniformity test of Section <905> is "content uniformity" which measures the variability in the amount of active drug contained in each capsule. Most pharmacies are not equipped to carry out content uniformity analyses since special analytical equipment is required.

It is possible to have capsules that pass the weight variation requirement but not have content uniformity. This can occur if the material put into the capsules is not a homogenous mixture of all the ingredients. Some capsules would then have more active drug than other capsules. Appropriate mixing (i.e., geometric dilution) of all capsule ingredients into a homogenous mixture before filling the capsules. In this manner, the weight variation data will be sufficient to ensure the quality of the capsules.