Home blood pressure monitoring and changes in plasma catecholamines during once or twice daily treatment with atenolol in patients with mild hypertension.

1. The effects of atenolol on diurnal blood pressure control, heart rate and plasma catecholamines were studied in nine hypertensives, six of whom also received diuretics. The patients completed a double-blind trial in which the effects of once and twice daily administration of atenolol were compared with placebo. 2. Atenolol (100 mg) given once a day produced significant reduction in diurnal blood pressures recorded at home but the effect was slightly less than either 50 mg given twice a day or 200 mg once a day. 3. Effects on heart rate and blood pressure were seen within 36 hours of the first dose, and were near maximal at 72 hours. After cessation of the drug, mean resting heart rate increased gradually and reached pre-treatment levels five days later, suggesting strong tissue binding of atenolol. Blood pressure increased more slowly over 8--10 days. 4. Plasma noradrenaline levels were increased at rest with atenolol. This argues strongly against the antihypertensive effect of atenolol being due to a reduction of sympathetic nerve activity. 5. Once daily administration of atenolol in this group of patients with mild hypertension produced satisfactory diurnal blood pressure control and beta blockade without "rebound" hypertension on cessation of therapy.