The Diskus: a new multi-dose powder device--efficacy and comparison with Turbuhaler

The Diskus is a novel multi-dose powder inhaler for the treatment of asthma, delivering precise individual doses of drug to allow the 'average' patient a month's therapy. It was designed to be simple to operate and contains a dose counter. The performance of the Diskus has been compared with that of a well-established reservoir powder inhaler. The pharmaceutical assessment of the Diskus has shown that the delivered dose of salmeterol and fluticasone propionate (FP) remains at approximately 90% of the labelled claim at a range of flow rates of 30-90L/min. This contrasts with data for the reservoir powder inhaler which show that the delivered dose as a percentage of the labelled claim is both lower and more variable, particularly at flow rates between 30 and 60L/min. The mass of drug substance (mass median aerodynamic diameter (MMAD)), < 6 microns) delivered from the Diskus also remains relatively constant at different flow rates, unlike the reservoir powder inhaler, in which the fine particle mass is more dependent on flow rate. The doses of drug in the Diskus are protected from moisture; the fine particle mass of salmeterol delivered from the Diskus is unaffected by humid conditions (30 degrees C/75% relative humidity) as opposed to the reservoir powder inhaler in which the ingress of moisture is associated with a decrease in particles of MMAD < 6 microns. In clinical studies, salmeterol, 50 micrograms twice daily, and FP, 50-500 micrograms twice daily, have been shown to be equally effective and well tolerated when delivered by Diskus as compared with Diskhaler.(ABSTRACT TRUNCATED AT 250 WORDS)