Comparison of the acute haemodynamic effects of bopindolol and propranolol at rest and during supine exercise

Beta-adrenergic blockade increases pulmonary vascular resistance and causes exaggerated hypoxic pulmonary vasoconstriction at high altitude: a physiological study

BACKGROUND

An increasing number of hypertensive persons travel to high altitude (HA) while using antihypertensive medications such as beta-blockers. Nevertheless, while hypoxic exposure initiates an increase in pulmonary artery pressure (Ppa) and pulmonary vascular resistance (PVR), the contribution of the autonomic nervous system is unclear. In animals, beta-adrenergic blockade has induced pulmonary vasoconstriction in normoxia and exaggerated hypoxic pulmonary vasoconstriction (HPV) and both effects were abolished by muscarinic blockade. We thus hypothesized that in humans, propranolol (PROP) increases Ppa and PVR in normoxia and exaggerates HPV, and that these effects of PROP are abolished by glycopyrrolate (GLYC).

METHODS

In seven healthy male lowlanders, Ppa was invasively measured without medication, with PROP and PROP + GLYC, both at sea level (SL, 488 m) and after a 3-week sojourn at 3454 m altitude (HA). Bilateral thigh-cuff release manoeuvres were performed to derive pulmonary pressure-flow relationships and pulmonary vessel distensibility.

RESULTS

At SL, PROP increased Ppa and PVR from (mean ± SEM) 14 ± 1 to 17 ± 1 mmHg and from 69 ± 8 to 108 ± 11 dyn s cm-5 (21% and 57% increase, P = 0.01 and P < 0.0001). The PVR response to PROP was amplified at HA to 76% (P < 0.0001, P[interaction] = 0.05). At both altitudes, PROP + GLYC abolished the effect of PROP on Ppa and PVR. Pulmonary vessel distensibility decreased from 2.9 ± 0.5 to 1.7 ± 0.2 at HA (P < 0.0001) and to 1.2 ± 0.2 with PROP, and further decreased to 0.9 ± 0.2% mmHg-1 with PROP + GLYC (P = 0.01).

CONCLUSIONS

Our data show that beta-adrenergic blockade increases, and muscarinic blockade decreases PVR, whereas both increase pulmonary artery elastance. Future studies may confirm potential implications from the finding that beta-adrenergic blockade exaggerates HPV for the management of mountaineers using beta-blockers for prevention or treatment of cardiovascular conditions.

Effects of bopindolol on platelet function in hypertension at rest and during exercise

The effects of bopindolol, a new nonselective beta-blocking agent, on platelet function have been studied in 10 male hypertensive patients given the drug (1 mg/day) in turn for eight weeks. Bopindolol significantly (p less than 0.01) decreased the bicycle exercise- (1.5 W/kg body weight for 6 minutes) induced increase in platelet aggregation. During bopindolol-treatment both the slope and the height of the platelet aggregation response curve were moderately decreased at rest before exercise and significantly (p less than 0.05) decreased at rest after exercise. During exercise the slope amounted to 75.4 +/- 44 degrees before and to 70.8 +/- 5.3 degrees after therapy (p less than 0.01), the height to 64.0 +/- 11.9% before and to 58.1 +/- 14.7% (p less than 0.05) after therapy. Furthermore, bopindolol significantly increased the exercise-induced decrease in platelet sensitivity to PGI2 (p less than 0.05; IC-50-value: 2.10 +/- 0.47 vs 1.88 +/- 0.31 ng/ml) and PGD2 (p less than 0.05; IC-50-value: (19.88 +/- 2.10 vs 18.57 +/- 1.63 ng/ml). Bopindolol also significantly (p less than 0.05) decreased the exercise-induced elevation in serum-TXB2 (244.9 +/- 35.2 vs 237.3 +/- 27.2 ng/ml) and plasma-TXB2 (15.7 +/- 6.3 vs 13.1 +/- 3.7 pg/ml). The platelet count, the plasma levels of 6-oxo-PGF1 alpha, beta-thromboglobulin (beta-TG) and platelet factor 4 (PF4) were not affected by bopindolol. It is concluded that bopindolol favourably affects platelet function, in that it lowers exercise-induced platelet aggregation and TXB2-formation in therapeutical doses and increases platelet sensitivity to antiaggregatory prostaglandins.(ABSTRACT TRUNCATED AT 250 WORDS)

Haemodynamic effects of bopindolol and atenolol in coronary artery disease. A noninvasive study

Bopindolol, a new non-selective betablocker, and atenolol, a conventional betablocker, were studied in parallel groups of eight normotensive patients with NYHA II-III angina pectoris. Non-invasive haemodynamic measurements were made using echocardiography and systolic time intervals. Drug doses were 1 mg bopindolol and 100 mg atenolol once daily; measurements were made immediately and at one and six weeks intervals. Both drugs reduced heart rate, atenolol from 62 to 47 beats/minute (24%, P less than 0.01) and bopindolol from 64 to 56 beats/minute (13%, P less than 0.05) at 24 hours. Only atenolol reduced mean blood pressure. Rate pressure product was persistently reduced by atenolol (30% at 24 hours), while with bopindolol this effect lessened with time. Opposite trends in left ventricular enddiastolic and endsystolic diameters were observed; with atenolol tending to increase and bopindolol to lower them. Atenolol had no influence on cardiac contractility, while bopindolol increased it, which was shown by enhancements in the fractional shortening, ejection fraction and maximum velocity of fibre shortening. Neither drug changed peripheral vascular resistance or systolic time intervals. Two patients on bopindolol left the study because of worsening symptoms of coronary artery disease, and two on atenolol owing to side effects, bradycardia and syncope in one and diarrhea in the other. In conclusion, bopindolol showed less beta-blocking effect than atenolol and it had a positive inotropic effect. Its benefit in treating coronary artery disease remains to be proved.

Comparison of bopindolol and atenolol in chronic stable angina pectoris

The efficacy of bopindolol and atenolol in the treatment of patients with chronic stable angina pectoris have been compared in a double blind, randomized study. Both bopindolol 1 mg and atenolol 100 mg for 6 weeks increased mean exercise time (25% and 22%, respectively, compared to placebo), time to angina (27% and 25%), and time to 1 mm of ST-segment depression (32% and 20%). Both drugs reduced ST-segment depression similarly at maximal and submaximal work levels. There was no significant difference in their antianginal efficacy.