Dynamic monitoring of total-body absorption by 19F NMR spectroscopy: one hour ventilation of HFA-134a in male and female rats

Twenty-eight-day double-blind safety study of an HFA-134a inhalation aerosol system in healthy subjects

A 28-day double-blind parallel group study has been conducted to compare the safety and tolerability of HFA-134a, a chlorofluorocarbon-free propellant in a pressurized metered-dose inhaler (MDI A), with a chlorofluorocarbon propellant (MDI C). Sixteen subjects were randomly assigned to receive one of the two MDIs, either four inhalations four times per day for 14 days or eight inhalations four times a day for 14 days, and were then crossed over to the alternative exposure regime with the same propellant for the next 14-day period. No clinically significant changes occurred in blood pressure, heart rate, electrocardiograms, pulmonary function (FEV1, FVC, FEF25-75%), haematology or serum chemistry. One subject in the MDI A group had elevated eosinophil counts throughout the study; there were no other remarkable clinical laboratory data. Fifty six adverse events were related to the study propellants; 34 of these occurred in the MDI C group and 22 in the MDI A group. For each adverse event no statistically significant differences were detected between propellant systems or between exposure levels. The most frequent adverse event was headache, which was reported by four subjects with each propellant system. Blood samples for HFA-134a in the MDI A group were collected on day 28 to measure systemic absorption. Blood levels of HFA-134a were detected in all subjects given this propellant within 1 min post-exposure, and these levels decreased to one-tenth of the original value by 18 min after the start of exposure. The safety and tolerability of an HFA-134a chlorofluorocarbon-free system was demonstrated over 28 days of exposure in healthy subjects. These negative results are clinically important because they indicate it will be safe to proceed with the study of this chlorofluorocarbon-free system in asthmatic patients.

Acute safety of the CFC-free propellant HFA-134a from a pressurized metered dose inhaler

The acute safety of the alternative chlorofluorocarbon-free (CFC-free) propellant HFA-134a from a pressurized metered-dose inhaler (MDI) was assessed in 12 healthy male subjects according to a double-blind, randomized, crossover design. On each of three consecutive days, cumulative doses of 1,2,4,8 and 16 inhalations were administered 30 min apart from one of three MDIs. The three MDIs contained either the HFA-134a CFC-free system without drug (HFA-Placebo), the CFC-free system with salbutamol sulphate (HFA-Salbutamol), or a conventional CFC propellant mixture without drug (CFC-Placebo). Pulmonary function (FEV1, FEF25-75%), cardiovascular performance (heart rate and blood pressure), objective tremor measurements and serum potassium were measured after each incremental dose. Similar responses for pulmonary function, cardiovascular performance, tremor and serum potassium were observed between the HFA-Placebo and CFC-Placebo groups. No statistically significant difference was seen in change from baseline of any parameter between the two propellant systems. The administration of HFA-Salbutamol produced statistically significant dose-related increases in heart rate, systolic blood pressure and tremor and a significant dose-related decrease in serum potassium; these responses were expected based on cumulative doses of active drug. Blood samples for HFA-134a analysis were collected to measure systemic absorption of this propellant. Levels of HFA-134a between 200 and 700 ng.ml-1 were detected in all subjects given the CFC-free system. This study shows that acute inhalation of HFA-134a in a CFC-free system is as safe as a CFC propellant system. Salbutamol sulphate in the CFC-free system can be delivered in a dose-linear fashion, without any noticeable change in the safety profile of active drug.