Haemodynamic Effects of Once Daily Atenolol in Essential Hypertension

The antihypertensive effects of once daily dosing with atenolol were assessed in 10 inpatients with essential hypertension (WHO I -III). In the pre-treatment period, indirect measurements of blood pressure and heart rate were prformed 15 times every hour form 07: 00 to 21: 00. The same measurements were taken during the treatment period, when atenolol was given for 7 days, 100 mg/day orally administered at 11. 30 a. m. Aten. olol as a hypotensive agent was effective in eight of the 10 patients and induced the overall reduction of blood pressure. Systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) in the 10 patients were reduced as average values of the recording taken one hour after atenolol therapy, although the decrease in DBP was statistically insignifi cant by 18: 00 hours. These results suggest that once daily dosing with atenolol maintained the therapeutic effect in essential hypertension over 24 hours.Haemodynamic studies (using radiocardiography) were carried out in 13 outpatients with essential hypertension (51±3yrs., WHO I-II) taking atenolol 100 mg once daily for 5 weeks, and in 15 patients taking metoprolol ay . 195 mg (120-240mg) daily in three divided doses for 5 weeks. Both atenolol and metoprolol reduced SBP (atenolol, from 177±6 mmHg to 153±mmHg, p<0.005 ; metoprolol, from 177±6mmHg to 153±6 mmHg, p<0.005), and reduced DBP (atenolol, from 103±3 mmHg to 89±3 mmHg, p<0.005 ; metoprolol, from 119±6 mmHg to 95±4mmHg, p<0.005) with a concomitant decrease in heart rate . Atenolol induced similar haemodynamic changes to those observed with metoprolol ; cardiac index (CI) fell from 3.95±0.34 l/min/m2 to 3.35±0.19 l/min/m2 (p<0.05) in the atenolol-treated group, and fell form 4.10±0.24 l/min/m2 to 3.30±0.22 l/min/m2 (p<0.05) in the metoprolol-treated group without any change in the total peripheral resistance (TPRI). However, in the total of 28 patients treated with atenolol or metoprolol, the decrease in mean blood pressure (MBP) did not correlate with the derease in CI, but correlated with the decrease in TPRI.This correlation between MBP and TPRI corresponds to that observed in pindolol therapy in our previous study. These results suggest that the antihypertensive effects of beta-adrenergic blockade depend mainly on the reduction of peripheral resistance, although the pharmacological properties of these beta-blockers are not uniform.