A randomized double blind study was designed by Bala and colleagues to ascertain if a combination of erythromycin with ranitidine is more effective than erythromycin alone or ranitidine-metoclopramide combination in reducing the gastric aspirate acidity and volume.

A total of 80 patients with ASA physical status I and II, aged between 18 and 60 years, who were undergoing elective surgery, were included in the study. Patients were segregated into 4 groups; each group had 20 patients. All the patients were administered the drug 60 to 90 minutes prior to surgery. PP group was given two placebo tablets; EP group was administered erythromycin 250 mg and placebo; ER group was given erythromycin 250 mg and ranitidine 150 mg; while RM group received ranitidine 150 mg and metoclopramide 10 mg.

Findings of the study –

• There was significantly higher gastric volume in PP group, compared to EP, ER, or RM groups (P < 0.001) (Table).
• No differences in volume of gastric aspirate were noted among EP, ER, and RM groups.
• Significantly lower gastric pH was noted in PP and EP groups, compared to ER and RM groups (P < 0.001) (Table).
• Considering both pH <2.5 and volume > 0.4 mL/kg, 45% of the patients in PP group were at risk for aspiration pneumonitis compared with zero patients in the other three groups (P < 0.001).

Table. Gastric pH and volume in study groups (mean + SD)

To conclude, erythromycin and ranitidine appears to be more effective in decreasing the acidity and volume of gastric fluid in comparison with erythromycin.

There seems to be no difference between erythromycin-ranitidine and ranitidine-metoclopramide combination.

Source: Bala I, Prasad K, Bhukal I, et al. Effect of preoperative oral erythromycin, erythromycin-ranitidine, and ranitidine-metoclopramide on gastric fluid pH and volume. J Clin Anesth. 2008 Feb;20(1):30-4.