Betaxolol kinetics in hypertensive children with normal and abnormal renal function.

The kinetic and clinical profile of betaxolol--a beta 1-selective blocker with 80% to 90% bioavailability and a 16 to 20 hr t1/2--were studied in ten children aged 5 to 13 yr with chronic renal hypertension and mild to severe renal failure. An IV dose of 20 mg of betaxolol per 1.73 m2 body surface area (BSA) was followed by six daily oral doses. Six patients were maintained on combination therapy and four on betaxolol alone; two of these were newly treated. After the intravenous dose, t1/2 (mean +/- SE) was 19.9 +/- 1.7 hr, total clearance 0.30 +/- 0.03 l/kg/hr, and volume of distribution 8.2 +/- 0.7 l/kg. Clearance adjusted for BSA was 7.9 +/- 0.6 l/hr. The t1/2 correlated linearly to serum creatinine levels. After the last dose, peak concentration was 97.4 +/- 7.6 ng/ml, and t1/2 19.4 +/- 2.7 hr. Betaxolol 24-hr blood levels were twice as high as after the first dose. Blood pressure was reduced in two newly treated patients and two patients on combination therapy; previous responses were maintained in the others. The maximum effect was reached after the first dose and was maintained throughout the study week. Our results indicate that betaxolol disposition in children aged 5 to 13 yr with different degrees of renal failure is of the same order as that in young healthy adults, implying that there may be a higher rate of non-renal clearance. Renal failure-induced modification led to a doubling of the t1/2 in the most severe cases, again as in adult renal patients. There is an antihypertensive effect.