Plasma Level Studies of Penbutolol After Oral Dose in Man

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Abstract
Plasma levels of penbutolol (HOE 893d) were determined in 8 healthy adult male subjects after oral administration of 50 mg capsules. Fast absorption of the drug from the gastrointestinal tract was indicated by the rapid increase in plasma levels during the absorption phase, with a peak time at about 1 h after dosing in all subjects. After the peak level, plasma concentrations declined biexponentially, with an average half-life of 2.5 and 27 h for the fast and slow disposition phases, respectively. These values were in good agreement with data previously found for this drug. Cumulative excretion of intact drug in the urine of the 8 subjects during 72 h after dosing was less than 4%, except for 1 subject who excreted 9.82% of the dose. Large individual variations were found for area under the plasma level curves, disposition rates and amounts of intact drug excreted in the urine. Significant pharmacologic effects were noted in all 8 subjects at the 50 mg dose level, and mild side effects were evident in 1/2 of these subjects. The average drop in blood pressure and pulse rate for all subjects was 26/18 mm Hg and 19 beats/min, respectively.