For adults with diarrhea in whom the origin is felt to be infectious, antibiotics (500 mg of ciprofloxacin by mouth as a single dose for onset of travelers' diarrhea or twice daily for 3 days) shorten the duration of illness by approximately 24 hours, regardless of the causative agent. Trimethoprim/sulfamethoxazole (one tablet of Bactrim DS by mouth as a single dose or twice daily for 3 days) also shortens the duration of infectious diarrhea in adults but is inferior to ciprofloxacin. Regardless of the causative agent, all patients (even those with negative Wright stain and negative stool culture) improve on ciprofloxacin. Combination treatment with Bactrim and loperamide is both safe and effective in treating traveler's diarrhea. Lomotil, a combination of diphenoxylate and atropine, was first approved by the FDA in 1960. Diphenoxylate is an oral, synthetic opiate agonist structurally related to meperidine. Atropine is added in small quantities to discourage deliberate abuse or overdosage of diphenoxylate. Despite its long-term availability, there is little data about comparative safety of Lomotil, although some experts suggest that it should be avoided in patients with a history of cardiac disease.