Betaxolol kinetics in hypertensive children with normal and abnormal renal function

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Abstract
The kinetic and clinical profile of betaxolol, a .beta.1-selective blocker with 80-90% bioavailability and a 16-20 h t1/2[half-life], were studied in 10 children aged 5-13 yr with chronic renal hypertension and mild to severe renal failure. An i.v. dose of 20 mg betaxolol/1.73 m2 body surface area (BSA) was followed by 6 daily oral doses. Six patients were maintained on combination therapy and 4 on betaxolol alone; 2 of these were newly treated. After the i.v. dose, t1/2 (mean) was 19.9 .+-. 1.7 h, total clearance 0.30 .+-. 0.03 l/kg per h, and volume of distribution of 8.2 .+-. 0.7 l/kg. Clearance adjusted for BSA was 7.9 .+-. 0.6 l/h. 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 h. Betaxolol 24 h blood levels were twice as high as after the 1st dose. Blood pressure was reduced in 2 newly treated patients and 2 patients on combination therapy; previous responses were maintained in the others. The maximum effect was reached after the 1st dose and was maintained throughout the study week. Evidently betaxolol dispostion in children aged 5-13 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 t 1/2 in the most severe cases, again as in adult renal patients. There is an antihypertensive effect.