Long-term gastric pH monitoring for determining optimal dose of ranitidine for critically ill preterm and term neonates.

AIM To determine the optimal doses of ranitidine for both preterm and term infants. METHOD The effect of ranitidine treatment was measured from the long-term intraluminal gastric pH in 16 preterm (gestational age under 37 weeks) and term infants treated in neonatal intensive care. The infants received three different bolus doses of ranitidine: 0.5 mg, 1.0 mg, and 1.5 mg per kilogram of body weight to keep the intraluminal gastric pH above 4 on a 24 hour basis. RESULTS Critically ill neonates, including very low birth weight infants, were capable of gastric acid formation, and ranitidine treatment increased the intraluminal gastric pH. The effect of a single dose lasted longer in preterm than in term infants. The time needed for reaching the maximum gastric pH was significantly longer in preterm than in term infants. The ranitidine given correlated with the duration of increased gastric pH in a dose dependent manner both in preterm and term infants. CONCLUSION Preterm infants need significantly smaller doses of ranitidine than term neonates to keep their intraluminal gastric pH over 4. The required optimal dose of ranitidine for preterm infants is 0.5 mg/kg/body weight twice a day and that for term infants 1.5 mg/kg body weight three times a day.