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Haemodynamic effects of metoprolol and pindolol: a comparison in hypertensive patients
Insights
This study found that both metoprolol and pindolol effectively lower blood pressure in hypertensive patients. Pindolol appears to work through peripheral vascular mechanisms, while metoprolol likely acts via central cardiac effects.
Area of Science:
- Cardiology and Pharmacology
- Hypertension Management
Background:
- Essential hypertension is a widespread condition requiring effective pharmacological treatment.
- Beta-blockers are a cornerstone in hypertension therapy, with different agents exhibiting varied mechanisms of action.
Purpose of the Study:
- To compare the hemodynamic effects of metoprolol and pindolol in patients with essential hypertension.
- To elucidate the potential mechanisms of blood pressure reduction for each drug.
Main Methods:
- A 6-month, double-blind, randomized study involving 36 patients with essential hypertension.
- Patients were treated with either metoprolol (100-300 mg/day) or pindolol (5-15 mg/day).
- Hemodynamic parameters, including blood flow and vascular resistance in calves and forearms, were measured using venous occlusion plethysmography.
Main Results:
- Both metoprolol and pindolol significantly reduced blood pressure within 6 weeks, with no further changes at 6 months.
- Metoprolol significantly decreased heart rate, while pindolol showed a significant reduction in heart rate after 6 months.
- Pindolol reduced calf vascular resistance and forearm vascular resistance at maximal vasodilation, suggesting peripheral vascular effects. Metoprolol primarily affected forearm vascular resistance at rest.
Conclusions:
- Pindolol lowers elevated blood pressure through peripheral vascular mechanisms.
- Metoprolol's antihypertensive effect is likely mediated by central cardiac mechanisms.
- Both drugs are effective in managing essential hypertension, but their distinct hemodynamic profiles suggest different therapeutic applications.
Abstract:
1 In a double-blind study, 36 patients with essential hypertension were randomly allocated to treatment with either metoprolol, 100--300 mg/day, or pindolol, 5--15 mg/day for 6 months. Haemodynamic investigations were made on three separate occasions. Blood flow in the calves and in the forearm was determined by venous occlusion plethysmography after 6 weeks of placebo, after 6 weeks and again after 6 months of active therapy. 2 Both drugs reduced blood pressure significantly, by 17.1/11.8 mm Hg with metoprolol and 21.9/10.9 mm Hg with pindolol after 6 weeks (P less than 0.005). No further changes were seen after 6 months. 3 Heart rate after 6 weeks was significantly reduced by metoprolol (10.7 +/- 2.4 beats/min, P less than 0.001) but not by pindolol (4.4 +/- 2.3 beats/min, NS). After 6 months a significant reduction was seen also in the pindolol group (5.2 +/- 2.1 beats/min, P less than 0.05). 4 The vascular resistance in the calves at rest was reduced by pindolol (P less than 0.05), whereas resistance tended to increase with metoprolol. 5 Resting vascular resistance in the forearm after 6 months was significantly reduced in the metoprolol group (P less than 0.001) as well as in the pindolol group (P less than 0.02). The increase in forearm vascular resistance seen during leg exercise was not influenced by either drug. 6 Vascular resistance at maximal vasodilatation was unchanged in the calves, but a significant reduction (-17.4 +/- 5.7%, P less than 0.01) in the forearm vascular bed was seen after 6 months of pindolol. No change was observed with metoprolol. 7 It is concluded that pindolol reduces elevated blood pressure partly through peripheral vascular mechanism. Metoprolol, on the other hand, probably acts mainly via central cardiac mechanisms.