The clinical pharmacology of oral and inhaled salbutamol

Abstract

The clinical pharmacology of 3 H‐salbutamol has been investigated in 12 asthmaltic patients. Peak plasma levels of between 212 and 489 nm. were seen at one to 3 hours after an oral dose (4 to 8 mg.) in 6 patients. The drug was well absorbed and 65 to 84 per cent of the dose was excreted in the urine. There was a correlation between plasma levels and one‐second forced expiratory volume (FEV 1 ) response. Peak plasma levels after inhalation of 3 H‐salbutamol (0.04 to 0.10 mg.) ranged from 2.55 to 5.69 nm. and were seen at 3 to 5 hours after inhalation; 78 to 97 per cent of the inhaled dose was excreted in the urine. The FEV, rose within 10 minutes of inhalation, and the results indicate that although the maiority of an aerosol dose is swallowed, bronchodilatation is due to local deposition of salbutamol in the lung. Salbutamol was excreted unchanged and as a maior metabolite (34 to 49 per cent of the dose) not previously seen in any animal species.