Comparative efficacy and potency of ipratropium via Turbuhaler and pressurized metered-dose inhaler in reversible airflow obstruction.

Ipratropium bromide (IB), typically delivered by pressurized metered dose inhaler (pMDI), is used to treat patients with reversible airways obstruction. Use of the pMDI, unlike the Turbuhaler (TH), demands co-ordination of actuation with inspiration for efficient use. Two studies were carried out to compare the relative efficacy and potency of IB delivered by TH or pMDI. Both studies were of a randomized, double-blind and cross-over design. For the efficacy study, 15 patients received a cumulative dose of 160 microg IB via TH or pMDI as doses of 20, 20, 40 and 80 microg at 45 min intervals on two days. Forced expiratory volume in one second (FEV1) was measured prior to and 40 min after dosing. For the potency study, 33 patients received 10, 20 or 40 microg of IB via TH, 20 microg IB via pMDI, or placebo, on five days. FEV1 was recorded prior to and 15-360 min after dosing. For the efficacy study, there was no difference in FEV1 response to a cumulative dose of IB via pMDI and TH. More than 80% of the maximum effect was seen at the lowest dose (20 microg of IB). Regarding the potency study, the FEV1 response to 20 microg IB administered via pMDI was similar to that of 10 microg via TH; 20 microg via TH was significantly more effective than 20 microg via pMDI (p<0.05). In conclusion, the efficacy study showed that maximum FEV1 occurred at low doses of IB, negating any opportunity to identify differences between devices. The potency study indicated that the 10 microg dose via TH was of similar efficacy to the 20 microg dose via pMDI, confirming an efficacy ratio of 1.5-2.0:1 for the TH device.