Antibiotics increase functional abdominal symptoms

Data suggest that subjects with irritable bowel syndrome are more likely to report a recent course of antibiotics. This study tests the hypothesis that a course of antibiotics is a risk factor for an increase in the number of functional bowel complaints over a 4-month period in a general population sample.

We initiated a prospective case-control study in three general practices in South London. Consecutive patients aged 16-49 attending their general practitioner with non-GI complaints and given a prescription for antibiotics were invited to participate. Comparison subjects who had not had antibiotics for 1 yr were identified from the practice records by age group, gender, and previous general practitioner visits. Fifty-eight antibiotic and 65 control patients agreed to participate. Questionnaires covering demographic, GI, and psychological data were sent at recruitment and at 4 months. Seventy-four percent of subjects completed the study. The number of symptoms at follow-up compared to that at recruitment.

Twenty of 42 antibiotic subjects (48%) versus 11/49 control subjects (22%) demonstrated one or more additional functional bowel symptoms at 4 months (unadjusted odds ratio = 3.14 [1.27-7.75]) (chi2 = 6.4, p = 0.01). Ten of 42 antibiotic subjects (24%) versus 3/49 control subjects (6%) demonstrated two or more additional functional bowel symptoms at 4 months (unadjusted odds ratio = 4.79 [1.22-18.80]) (chi2 = 5.8, p = 0.02).

Functional bowel symptoms come and go, but subjects who are given a course of antibiotics are more than three times as likely to report more bowel symptoms 4 months later than controls.