Prevention of neonatal hyperbilirubinemia in rhesus monkeys by tin-protoporphyrin.

Rhesus monkey infants were injected subcutaneously at birth with 12 to 100 mumol of tin-protoporphyrin IX, a competitive inhibitor of microsomal heme oxygenase. The elevated unconjugated serum bilirubin levels of the neonates receiving this metalloporphyrin rapidly declined to near adult levels by 24-30 h. Control neonates which received an injection of saline exhibited normal physiologic hyperbilirubinemias of from 3-6 mg/dl by 12-24 h as expected. These studies establish the effectiveness of tin-protoporphyrin IX in depressing bilirubin production and preventing physiologic hyperbilirubinemia in simian neonates. Two of six animals receiving the metalloporphyrin exhibited signs of toxicity.