Pharmacokinetic differences between chlorofluorocarbon and chlorofluorocarbon-free metered dose inhalers of beclomethasone dipropionate in adult asthmatics.

We have compared the serum pharmacokinetics of the metabolites of beclomethasone dipropionate after inhalation from chlorofluorocarbon (CFC) and hydrofluoroalkane HFA-134a (HFA) formulations in asthmatic patients. Twenty-three patients completed this open-label, randomized, single-dose, three-period crossover study. Each patient received in separate periods 200 microg or 400 microg HFA-beclomethasone dipropionate, or 400 microg CFC-beclomethasone dipropionate. Venous blood samples were collected over 24 h for the determination of beclomethasone esters and beclomethasone in the serum. Significant differences in pharmacokinetics following HFA- and CFC-beclomethasone dipropionate were observed. Following a 400 microg beclomethasone dipropionate dose, the HFA formulation gave mean maximum concentrations (Cmax) and area under the curve (AUC) values of beclomethasone esters of 1153 pg mL(-1) and 4328 pg h mL(-1), respectively, and beclomethasone Cmax and AUC values of 69 pg mL(-1) and 682 pg h mL(-1), respectively. These values were approximately 2-3-fold those seen with the CFC formulation (beclomethasone esters Cmax and AUC of 380 pg mL(-1) and 1764 pg h mL(-1), respectively; beclomethasone Cmax and AUC of 41 pg ml(-1) and 366 pg h mL(-1), respectively). Beclomethasone esters, the major component of beclomethasone dipropionate in the serum, peaked significantly earlier for the HFA formulation (0.8 h) than for the CFC formulation (2 h). Tests for dose proportionality of beclomethasone esters pharmacokinetics following HFA-beclomethasone dipropionate showed that the two hydrofluoroalkane strengths were proportional. The more rapid and greater efficiency of systemic drug delivery of the HFA formulation compared with the CFC formulation can be explained if most of each inhalation from CFC-beclomethasone dipropionate is swallowed and absorbed orally, whereas most of each inhalation from HFA-beclomethasone dipropionate is absorbed through the lungs. There is a need for comprehensive dose-response efficacy trials, with the use of the steep portion of the dose-response relationship, to evaluate the significance of these pharmacokinetic differences.