Clinical pharmacokinetics of procaterol: dose proportionality after administration of single oral doses

Procaterol is a potent, orally active beta 2-agonist bronchodilator useful in the treatment of reversible bronchospastic disease. It is effective when administered as single or multiple (Q8H) 50 and 75 micrograms doses. As part of the clinical development of procaterol, the pharmacokinetics and dose proportionality of single 25, 50, 75, and 100 micrograms doses were investigated in 14 healthy subjects. Serial blood samples were collected for 16 h and urine was quantitatively collected for 48 h following administration of each dose. Procaterol concentrations in plasma and urine were determined using sensitive and specific radioimmunoassay methods. Mean values for tmax, the apparent elimination rate constant, Cl/F, renal clearance, and per cent of dose excreted unchanged in urine were similar for all doses. Dose-normalized AUC, Cmax, and amount excreted unchanged in urine (Ae) were also similar across dosage levels. Thus, the pharmacokinetics of procaterol appear to be proportional to dose over the range of doses studied.