A Comparison of the Puncturing Properties of Gelatin and Hypromellose Capsules for Use in Dry Powder Inhalers

Abstract

This study investigates capsule puncture in dry powder inhalers. Gelatin and hydroxypropylmethyl cellulose (HPMC) capsules (stored at 11 and 33% relative humidities) were punctured using a pin from a Foradil® inhaler, with insertion force measurement via an Instron tester. In HPMC capsules, the force after capsule puncture reduced by half and then increased to a second maximum as the pin shaft entered the hole. In gelatin capsules, the postpuncture force reduced to zero, indicating shell flaps losing contact with the pin. At lower moisture contents, both capsules were less flexible. This provides a tool to measure the shell properties of inhalation capsules.

Keywords:

• capsule
• puncture
• dry powder inhaler
• gelatin
• HPMC

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Erratum