Agonist Activity: Clinical Pharmacological Considerations

1 Pindolol is a ,B-adrenoceptor antagonist equally effective on land P2-adrenoceptors which has a relatively long duration of action. It is practically completely absorbed and, unlike most other P-adrenoceptor blockers, is only metabolized to a small extent during the first passage through the liver. 2 Pindolol possesses partial agonist activity (intrinsic sympathomimetic activity, ISA). This means that apart from blocking P-adrenoceptors it produces some stimulation. Pindolol therefore only slightly influences normal sympathetic drive at rest but effectively reduces the effects of elevated sympathetic activity. 3 Various therapeutic advantages have been attributed to the partial agonist activity of pindolol: no or only slight alterations in normal cardiac output, heart rate and peripheral blood flow occur. Peripheral resistance is reduced during chronic oral therapy. No alteration ofHDL/LDL cholesterol ratio has been observed. Rebound phenomena on sudden withdrawal of therapy and bronchoconstriction in susceptible patients are less likely than with drugs devoid of ISA.