Systemic Concentrations of Salbutamol and HFA-134a After Inhalation of Salbutamol Sulfate in a Chlorofluorocarbon-Free System

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Abstract
The objective of this study was to determine if salbutamol was absorbed from a new salbutamol sulfate chlorofluorocarbon (CFC)-free metered-dose inhaler (MDI). Measurement of HFA-134a, the CFC-free propellant, was included to provide proof of delivery of this MDI. Eight healthy men received two inhalations (90 micrograms salbutamol base equivalents per inhalation ex adapter) from the CFC-free inhaler (MDI A) in period 1 and from a reference CFC inhaler (MDI V) in period 2. Eight postdose samples were collected for the determination of salbutamol serum levels over a 4-h period. Salbutamol levels were not quantifiable in most samples. Four subjects given MDI A and two given MDI V had a few transient salbutamol levels, which occurred in the first hour after dosing, within a narrow range of 1-2 ng/ml and close to the lower limit of detection (1 ng/ml). No pharmacokinetic analyses were possible. Blood samples were also collected after MDI A for propellant quantitation. HFA-134a levels were seen in all subjects, verifying absorption. We conclude that the transient salbutamol serum levels can be attributed to the two-inhalation dose and not to either propellant system.