Intervention, Group Assignment, and Concealment

The intervention consisted of chewable tablets each containing 262 mg of BSS (Pepto-Bismol InstaCool Peppermint; Procter & Gamble). Placebo, produced by the manufacturer of the intervention drug, was identical in appearance, flavor, and packaging but did not contain BSS. Each patient received 32 tablets of the study drug. We instructed participants to take 2 tablets every 30 to 60 minutes as needed for diarrhea, not to exceed 8 doses (16 tablets) per day during the first 48 hours after enrollment. Patients were asked to discontinue the medication when stools became formed. Study staff administered the initial dose of the study medication as directly observed therapy at enrollment; participants were given verbal, written, and pictorial instructions and self-administered subsequent doses as outpatients. All participants also received 2 sachets of oral rehydration solution and instructions for how to prepare and use it.

Participants were randomized 1:1 to BSS or placebo. One of us (A.B.) assigned the allocation sequences, stratified by clinic, using an Excel spreadsheet (Microsoft Corp) to generate random numbers. This investigator labeled masked vials of BSS and placebo by clinic according to the allocation sequence and did not participate in patient selection, data collection, or data entry. We enrolled 20 patients per clinic. Group assignment was triple masked, or concealed from participants, physicians and data collectors, and the principal statistician (B.P.), until primary analysis was complete. While study physicians were asked not to provide antibiotics to participants during the enrollment visit, neither they nor the participants were told the precise purpose of the study.