Alprenolol in hypertension

Decreased plasma concentrations and clinical effects of alprenolol during combined treatment with pentobarbitone in hypertension

The antihypertensive effect of alprenolol has been studied before, during and after additional pentobarbitone treatment. The combined alprenolol-pentobarbitone treatment significantly decreased alprenolol levels by 59% and 4-hydroxyalprenolol by 24%. The effect was significant after three doses and declined over 4-5 days after pentobarbitone withdrawal. The decreased alprenolol plasma levels were associated with increased pulse rate (6%), and systolic (8%) and diastolic (9%) blood pressure. The inhibition of exercise tachycardia by alprenolol was reduced by 18% at the end of pentobarbitone treatment compared to initial monotherapy with alprenolol. The interaction is probably clinically important in those patients with hypertension and angina pectoris that are treated with barbiturates and alprenolol.

Pharmacokinetics and pharmacodynamics of alprenolol in the treatment of hypertension. I. Relationship between plasma concentration and adrenergic beta-receptor blockade

Mean steady-state plasma concentrations of alprenolol were studied in relationship to the degree of beta-blockade, in sixteen patients receiving 600 mg daily in divided doses. Steady-state alprenolol concentrations were determined from the area under the plasma concentration-time curve during one eight-hour dosage interval after treatment for six weeks. Beta-blockade during alprenolol treatment was assessed from the chronotropic response to intravenous isoprenaline compared to the response after six weeks of placebo therapy. Although there was interindividual variability in the mean steady-state alprenolol concentration (range 11 - 141 ng/ml), and in the degree of beta-blockade (7-fold), the correlation between the two variables was highly significant (r = 0.80, p less than 0.001). The prescribed dose of alprenolol (mg/kg) was not significantly correlated with the plasma level of alprenolol or the beta-blockade. The chronotropic effects of isoprenaline during placebo and alprenolol were significantly interrelated (r = 0.79, p less than 0.001).