Plasma propranolol levels in adults With observations in four children

Abstract

Plasma levels of the f3‐adrenergic‐blocking drug, propranolol, have been measured fluorometrically in man after oral and intravenous administration. Following oral administration, peak plasma levels in 5 sub/ects varied sevenfold, while, after intravenous administration, levels in the same sub/ects varied only twofold, indicating considerable variability among individuals in the amount of drug reaching the systemiC circulation after oral administration. However, plasma levels were relatively constant in sub/ects given repeated, single doses. The plasma half‐life of the drug was 2.3 hours after intravenous administration. A plasma half‐life of 3.2 hours was found after oral administration; its greater duration was attributed to continuing absorption. After intravenous administration, the rate of decline of the levels of propranolol in the plasma was biexponential, and the volume of distribution during the late phase of elimination was found to be about 150 liters, indicating concentration of the drug in the tissues. The drug was administered orally to 4 children at dose levels calculated on the basis of body weight and on the basis of body surface area. It was found that a dose intermediate to the two tested would be required to obtain plasma levels approximating the average level in adults given an equivalent dose.