Evaluation of flow properties of dry powder inhalation of salbutamol sulfate with lactose carrier

The effects of the flow and packing properties of a drug/carrier powder mix ture on emission of drug adhering to the carrier from capsules and inhalati on devices were investigated. Model powder mixtures were designed consistin g of lactose carriers with different particle shapes were prepared by surfa ce treatment and micronized salbutamol sulfate. These powder mixtures were aerosolized by a Spinhaler (R), and in vitro deposition properties of salbu tamol sulfate were evaluated by a twin impinger. The flow properties of the mixed powders were evaluated by the Carr's flowability index (FI) and Haus ner's ratio (HR). The packing properties of the mixed powders were determin ed employing the tapping method. Compared with the powder mixed with the un treated lactose carrier, the FI, HR, and the constant K in Kawakita's equat ion of the powder mixture prepared using the surface-treated lactose carrie r were significantly different, showing that the flow and packing propertie s of the drug/carrier powder mixture were improved. Using this surface-trea ted system, the handling of the powder mixture when packing into capsules i s improved, which is desirable for handling dry powder inhalants. The fract ion (%) of drug emitted from capsules and devices (EM) and the FI of the po wder mixture were correlated. As the flow properties improved, the outflow of the powder mixture from capsules and devices became easier, and emission of drug adhering on the carrier from capsules and devices improved. Improv ement of the inhalation process, such as the drug particles emitted from th e inhalation system, is valuable for increasing inhalation properties of dr y powder inhalation.