Single and divided doses of penbutolol

Area of Science:

• Pharmacology
• Cardiovascular Medicine

Background:

• Penbutolol is a nonselective beta-adrenoreceptor antagonist.
• Understanding its pharmacokinetic and pharmacodynamic profile is crucial for therapeutic use.

Purpose of the Study:

• To evaluate the duration of action and dose-response relationship of penbutolol.
• To investigate the effects of repeated dosing and identify factors influencing its absorption and activity.

Main Methods:

• Single and multiple oral doses of penbutolol (40 mg and 2x20 mg) were administered.
• Exercise-induced heartbeats were measured to assess beta-adrenoceptor blockade.
• Serum concentrations of penbutolol were monitored over time.

Main Results:

• A single 40-mg oral dose reduced exercise-induced heartbeats for at least 24 hours.
• No significant changes in pharmacodynamics or pharmacokinetics were observed with 7-day ingestion; no drug accumulation occurred.
• A correlation was established between serum penbutolol concentrations and heart rate reduction.
• Evening administration showed reduced absorption, and prolonged activity suggested potential metabolite contribution.

Conclusions:

• Penbutolol exhibits a prolonged duration of action after a single oral dose.
• Its pharmacokinetics and pharmacodynamics are stable with repeated dosing, with no evidence of accumulation.
• Further research is warranted to explore the role of metabolites in penbutolol's sustained beta-adrenoceptor blockade.