[Interaction of tolazoline and cimetidine in persistent fetal circulation of the newborn infant].

A newborn was treated with tolazoline for persistent pulmonary hypertension. Oxygenation improved during continuous infusion of the drug, but gastrointestinal bleeding occurred. Therefore, cimetidine was given. After this there was a rapid deterioration with decrease of oxygen saturation and arterial pO2 values. Tolazoline induces a dilatation of the pulmonary vascular system by stimulating H1 and H2 receptors. Blocking of H2 receptors by cimetidine abolishes the effect of tolazoline at least partially. Our case shows that the interaction between tolazoline and cimetidine is of clinical significance. The recommendation to use cimetidine as prophylaxis against gastrointestinal side-effects induced by tolazoline can no longer be maintained.