Caution with use of cimetidine in tolazoline induced upper gastrointestinal bleeding.

A 2-day-old newborn was treated with tolazoline for persistent pulmonary hypertension due to meconium aspiration syndrome. Hypoxemia improved during continuous tolazoline infusion, but gastrointestinal bleeding occurred. After treatment with cimetidine, there was a rapid deterioration with decreased oxygen saturation and arterial PO2 values. Tolazoline induces a dilatation of the pulmonary vascular system by stimulating H2 receptors. Cimetidine, an H2 blocker, may partially abolish the effect of tolazoline. However, given the clinically significant result to the interaction between tolazoline and cimetidine we report, the use of cimetidine in tolazoline induced upper gastrointestinal hemorrhage should deserve more attention.