Relationship between blood level of atenolol and pharmacologic effect.

Thirty-five hypertensive patients were treated with atenolol in weekly increasing doses (25, 50, 100, and 200 mg thrice daily). Factors determining the blood level of the drug were studied along with the relationship between blood level, the degree of cardiac beta blockade, and the antihypertensive effect of the drug. The blood level obtained varied with the daily dose, the time of blood sampling during the day, the body weight, and the creatinine clearance. The degree of beta blockade was assessed by measuring maximum-exercise tachycardia and was correlated with the blood level of atenolol. The reduction of the maximum exercise heart rate was independent of age. The hypotensive effect was not closely correlated with the blood level. Three days after the termination of long-term atenolol treatment, blood levels and beta blockage were still detectable.