Abstract
Tolazoline has been reported to reduce the elevated pulmonary vascular resistance found in some clinical conditions, including the syndrome of persistence of the fetal circulation in the newborn. Tolazoline, an ≥-adrenergic blocking agent, also has direct actions on cardiac and smooth muscle which are described as “histamine-like.” We evaluated the pulmonary vasodilator effect of tolazoline in newborn lambs before and after the administration of the specific histamine H1- and H2-receptor antagonists, diphenhydramine and metiamide, respectively. Lambs, 0-3 days old, were anesthetized and instrumented for measurement of pulmonary artery pressure, left atrial pressure and pulmonary blood flow. Pulmonary vascular resistance, PVR, was then calculated. Pharmacologic agents were administered in bolus form via the inferior vena cava in the following doses: tolazoline, 1 mg/kg; diphenhydramine, 5 mg/kg; and metiamide, 5 mg/kg. The mean change in pulmonary vascular resistance, %ΔPVR, produced by tolazoline after histamine receptor blockade is given below.
It is concluded that the pulmonary vasodilator action of tolazoline is entirely mediated by histamine H1- and H2 receptors.
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Goetzman, B., Milstein, J. & Wennberg, R. 1184 PULMONARY VASODILATOR ACTION OF TOLAZOLINE IN THE NEWBORN. Pediatr Res 12 (Suppl 4), 561 (1978). https://doi.org/10.1203/00006450-197804001-01190
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DOI: https://doi.org/10.1203/00006450-197804001-01190