Dry powder inhalation of colistin sulphomethate in healthy volunteers: A pilot study

Pulmonary administration of the antimicrobial drugs colistin sulphomethate and tobramycin has been shown to be effective in slowing down pulmonary deterioration in cystic fibrosis (CF) patients. Both drugs are administered by liquid nebulisation, a technique known to have disadvantages. Dry powder inhalation may be an attractive alternative. We investigated inhalation of colistin sulphomethate dry powder using a newly developed Twincer® device in healthy volunteers. Eight healthy volunteers inhaled a single dose of 25mg colistin sulphomethate dry powder each, using the Twincer® inhaler. The median diameter (X50) of the dry powder was 1.6μm (X10=0.7μm, X90=3.1μm), measured by laser diffraction technique. Pulmonary function tests were performed before, 5 and 30min after inhalation. Serum samples were drawn at t=15min, 45min, 1.5h, 2.5h, 3.5h, 5.5h, 7.5h and 24h after inhalation. The colistin sulphomethate dry powder inhaler was well tolerated: no clinically relevant effect on FEV1 was observed nor did the volunteers experience adverse effects. Dry powder inhalation of colistin sulphomethate using the Twincer® inhaler is well tolerated by healthy volunteers. A pilot study in cystic fibrosis patients is therefore considered safe in developing a dry powder inhalation of colistin for everyday CF treatment.