Both ranitidine and cimetidine are effective drugs for reducing gastric acidity. However, ranitidine may be a better agent.

A study by Mahachai et al assessed the 24-hour intragastric pH and serum gastrin profiles of 6 asymptomatic men who previously had esophagitis, confirmed by endoscopy and biopsy. The study participants were administered cimetidine 300 mg qid, ranitidine 150 mg bid, or placebo for one week each. The mean basal acid output (BAO) was 0.4±0.2 mmol/hr, and the mean maximal acid output (MAO) in response to pentagastrin was 21.2±3.2 mmol/hr.

• Among the patients treated with placebo, the pH varied between 1.8 and 3.5. More than 90% of the readings were below pH 4.
• In comparison with placebo, treatment with cimetidine and ranitidine led to a significant suppression of H⁺ post breakfast, overnight, and over the entire 24-hr period.
• The mean post lunch pH was found to be significantly higher with ranitidine compared with placebo.
• Over the 24-hr period, a higher percentage of the values were greater than pH 4.0 with ranitidine compared to cimetidine.
• During nighttime, 50% of the pH values were above pH 4.0 with ranitidine and cimetidine, while with placebo, 50% of the pH readings were below pH 2.0.
• The integrated gastrin responses after every meal were similar with ranitidine and cimetidine, but greater than placebo.
• The biphasic response of the ratio of H+ and gastrin (H+/G) after each meal was suppressed by both the drugs, with lower values seen with ranitidine than with cimetidine.

The study concluded that ranitidine 150 mg twice a day is better than cimetidine 300 mg four times a day for suppression of 24-hr intragastric acidity.

Source: Mahachai V, Walker K, Thomson ABR, et al. Comparison of cimetidine and ranitidine on 24-hour intragastric acidity and serum gastrin profile in patients with esophagitis. Digest Dis Sci. 1985;30:321–328.