The Pharmaceutics and Compounding Laboratory

Single Punch Tablet Machines

Tableting machines are commonly used in pharmaceutical industry. They are high-speed machines that create thousands of tablets in a small period. The compounding pharmacist uses a variation of these machines. It is called a single-punch tablet press and makes one tablet at a time. A "punch" has two pieces of casted tubular metal. The bottom metal piece has a small cavity in one end of the tube; the top metal piece has one end that is tapered into a small rod that will just fit into the small cavity in the other piece. The rod does not go all the way to the bottom of the cavity, but leaves a small gap. The punch is fitted into a press so that when the handle is depressed and released, the rod goes into and then comes out of the bottom piece. To make a tablet, the powder material is placed into the bottom piece, and the handle is depressed and released. The powders are compressed and occupy the size of the gap designed in the punch.

Punches come in many sizes which allows the production of tablets of different sizes and compression strengths. But each punch is a matched set; it is not possible to interchange the top and bottom pieces of different punches.

Chewable tablets, effervescent tablets, and compressed tablets can be made using a tablet press. Chewable tablets are generally made using mannitol because it has a sweet, cooling taste and is easy to manipulate. Other ingredients may include binders (e.g., acacia), lubricants (e.g., stearic acid), colors, and flavors. The powder mixture is prepared, the desired quantity of mixture is weighed, and then pressed with a single-punch tablet machine.

Effervescent tablets generally contain ingredients such as tartaric acid, citric acid, and sodium bicarbonate. These powders would be appropriately mixed and pressed into tablets using the same procedure as chewable tablets. They will not require a disintegrant since they will effervesce when placed in water. Compressed tablet mixtures generally contain the active drug, a diluent (e.g., lactose), a disintegrant (e.g., starch), and a lubricant (e.g., 1% magnesium stearate).