The Pharmaceutics and Compounding Laboratory

"Punch" Method of Compounding Capsules

To hand fill capsules at the prescription counter, the pharmacist generally uses the "punch" method. The ingredients are triturated to the same particle size and then mixed by geometric dilution. The powder is placed on a powder paper or ointment slab and smoothed with a spatula to a height approximately half the length of the capsule body. The base of the capsule is held vertically and the open end is repeatedly pushed or "punched" into the powder until the capsule is filled; the cap is then replaced to close the capsule. Each filled capsule is weighed using an empty capsule as a counterweight. Powder is added or removed until the correct weight has been placed in the capsule. The filled capsule is tapped so that no air spaces are visible within the contents.

Video View a video demonstration on capsule punching

It is a good practice to remove from the stock container the exact number of empty capsules needed before you begin filling them. In this way you avoid preparing the wrong number of capsules and at the same time avoid contaminating the empty capsules with drug particles that cling to your hands. Also, since some fill material will likely be lost in the process of punching capsules, the pharmacist generally calculates for the preparation of at least one extra capsule to insure enough fill for the last capsule.

The simplest method by which a capsule may be kept free of moisture during compounding is to wash the hands well, dry them, and keep the fingers dry by stripping a towel through the cleansed fingers until warmth is felt. An alternative method is to use the base of one capsule as a holder for other bases during the filling operation. The capsules do not come in contact with the fingers. The most sure method of protecting the capsule is to wear finger cots or rubber gloves.