Abstract
To clarify the hemodynamic effects of the newly introduced analgesic, pentazocine, 30 dogs were studied with a right heart bypass preparation using an isovolumetric balloon technique. Heart rate and coronary artery perfusion pressure were held constant. After the rapid intravenous administration of 2.5 mg. per kilogram of pentazocine the left ventricular pressure (LVP) increased by 28 per cent, LV dp dt max. increased by 46 per cent, and the forcevelocity curve was shifted upward and to the right indicating a positive inotropic effect. The increase in contractility was noted 5 to 10 minutes after pentazocine injection and was sustained for 45 to 60 minutes. This reaction was blocked by the prior administration of propranolol, but was unaffected by previous catecholamine depletion with reserpine. All animals exhibited a transient fall in peripheral vascular resistance of 42.5 per cent within 2 minutes after pentazocine administration, but resistance returned to baseline levels within 3 minutes. Coronary blood flow and myocardial oxygen consumption were unaltered. These data indicate that pentazocine has a beta-stimulating inotropic effect, and, therefore, it may be particularly useful for providing analgesia in patients with impaired myocardial contractility. The usefulness of the drug in such patients must, however, be assessed in appropriate clinical studies.
Published Version
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