Comparison of pirenzepine, ranitidine, and pirenzepine-ranitidine combination for reducing preoperative gastric fluid acidity and volume in children.

We conducted a two-part controlled study to evaluate the efficacy of preoperative oral pirenzepine (muscarinic receptor antagonist known to inhibit gastric secretion), ranitidine, and the combination pirenzepine-ranitidine in controlling gastric fluid pH and volume in 210 ASA I children, aged 2-14 yr, undergoing elective surgery. In the first part of the study (n = 90), the proportion of children considered at risk for aspiration pneumonitis was reduced with pirenzepine 25 mg (P < 0.05) but not with 12.5 mg. In the second part of the study, the other 120 children were allocated randomly to one of four groups: pirenzepine 25 mg with placebo; ranitidine 75 mg with placebo; pirenzepine 25 mg with ranitidine 75 mg; and placebo and placebo. These medications were administered 1 h before anaesthesia. After tracheal intubation, volume and pH of the gastric fluid aspiration via a multiorifice orogastric tube were measured. Pirenzepine 25 mg decreased gastric fluid volume (P < 0.05) but failed to increase gastric pH. Ranitidine 75 mg increased gastric pH (P < 0.05) but failed to decrease fluid volume. The pirenzepine-ranitidine combination reduced gastric fluid acidity and volume (P < 0.05).