CLINICAL EFFECT OF DISKUS(TM) DRY-POWDER INHALER AT LOW AND HIGH INSPIRATORY FLOW-RATES IN ASTHMATIC-CHILDREN

In vitro studies with the Diskus(TM) inhaler at low and high flow rate s show consistent doses of drug as fine particles <4.7 mu m. The prese nt study was designed to ascertain whether this in vitro flow independ ency translates into flow-independent clinical effect when the device is used by patients at low (30 L.min(-1)) and high (90 L.min(-1)) flow rates. A pilot study in 129 children aged 3-10 yrs demonstrated that 99% of children of 3 yrs and above can generate a flow greater than or equal to 30 L.min(-1) through the device, while 26% performed greater than or equal to 90 L.min(-1). Eighteen children aged 8-15 yrs with e xercise induced asthma inhaled placebo or salmeterol 50 mu g at either 30 L.min(-1) or 90 L.min(-1). Exercise challenges were carried out 1 h and 12 h after dosing, The maximum percentage fall in forced expirat ory volume in one second (FEV1) after exercise 12 h after treatment wa s significantly less after salmeterol at either flow rates as compared to placebo, There was no significant difference in the protection fro m salmeterol on the day of low-flow inhalation results the day of high -flow inhalation. Consistent in vitro fine particle dosing from the Di skus(TM) inhaler translates into a consistent clinical effect at low a nd high flow rates in children.