Scintigraphic comparison of budesonide deposition from two dry powder inhalers

Chlorofluorocarbons (CFCs), used in metered dose inhalers (MDIs), have been identified as being deleterious to the environment leading to a ban on the ir production. Dry powder inhalers (DPIs) are a widely used alternative to MDIs, One disadvantage of DPIs is that in vivo lung deposition can be influ enced by the patient's inspiratory flow rate, The ASTA Medica multi-dose dr y powder inhaler (AM-MDPI) has been designed to offer low resistance on inh alation, so that asthmatic patients can achieve inhaled flow rates of simil ar to 90 L.min(-1) The aim of the study was to evaluate the in vivo deposition of budesonide f rom the AM-MDPI at different flow rates and to compare this with delivery f rom a Turbuhaler DPI at a high flow rate. The study was a scintigraphic, ra ndomized, crossover study in which 13 healthy volunteers inhaled a single 2 00 mu g dose of radiolabelled budesonide on four separate occasions with a minimum 44-h washout period between dosings. At the lowest flow rate of 54 L.min(-1) comparable to that for the Turbuhal er (58 L.min(-1)), a similar percentage of the metered dose was delivered t o the lung (AM-MDPI median 19.9%; Turbuhaler median 21.4%). At high flow ra te (peak inspiratory flow rate 99 L.min(-1)) the AM-MDPI delivered signific antly more drug to the lung (median 32.1% of metered dose) than at 65 L.min (-1) or 54 L.min(-1) (median 25.0% and 19.9% of metered dose, respectively) , thus demonstrating flow rate dependence. The pattern of regional lung dep osition from the AM-MDPI was similar for all three inhalation manoeuvres. It was concluded that the ASTA Medica multi-dose dry powder inhaler achieve s at least as much deposition of budesonide in the lungs as a Turbuhaler wh en used at similar inspiratory flow rates.