Investigations into the use of pregelatinised starch to develop powder-filled hard capsules.

The use of pregelatinised starch in tamp filling of hard capsules with powder formulations containing a low-solubility drug (theophylline anhydrous) with very poor powder flow and stickiness to metal surfaces was investigated. Twenty-one mixtures containing the drug, pregelatinised starch, lactose monohydrate and magnesium stearate were produced, with their quantitative composition based on a central composite design. These mixtures were filled into hard capsules using an instrumented tamp-filling machine. Seven different compression settings ranging from "no" to "firm" compression were employed, and the tamping force was recorded on stations 3 and 4. It was found that the use of pregelatinised starch as an excipient in the manufacture of powder-filled hard capsules could be beneficial in terms of reducing the coefficient of fill weight variability. To improve drug dissolution of poorly soluble drugs, larger amounts of this excipient were required, and the maximum capsule fill weight that could be achieved was slightly reduced at the same time.