A study by Guay and colleagues evaluated the effects of orally administered cimetidine and ranitidine on gastric pH and gastric residual volume in children scheduled for elective surgery.

The study included 60 children, aged 2-6 years, who were randomly allocated to four groups – Group 1 received 7.5 mg/kg cimetidine, Group 2 was given ranitidine 1.5 mg/kg, Group 3 received ranitidine 2.0 mg/kg, and Group 4 was given a placebo.

• Both cimetidine and ranitidine given 1-2 h before induction of anesthesia were effective in increasing gastric pH - 5.47 +85 in group 1, 4.92 + 2.1 in group 2, 5.30 + 1.82 in group 3, compared to 1.75 + 0.58 in group 4 (P < 0.001).
• A single dose of ranitidine 1.5 mg/kg appeared to be as effective as ranitidine 2.0 mg/kg and cimetidine 7.5 mg/kg.
• Volume > 0.4 ml/kg and pH < 2.5 was noted in 33% of patients in the placebo group. However, no patients in any of the treatment groups had a combination of volume > 0.4 ml/kg and pH < 2.5 (P < 0.001).

Both ranitidine and cimetidine increased gastric pH in children.

A single ranitidine dose of 1.5 mg/kg was as effective as cimetidine 7.5 mg/kg.

Source: Guay J, Santerre L, Gaudreault P, et al. Effects of oral cimetidine and ranitidine on gastric pH and residual volume in children. Anesthesiology. 1989 Oct;71(4):547-9.