Long-term gastrointestinal adverse effects of doxycycline

Introduction: Doxycycline is an antibiotic with known gastrointestinal (GI) adverse effects. Esophagitis is the most pronounced among these effects, and might be associated with a prolonged duration of therapy. The aim of this study is to evaluate the incidence of esophagitis and other GI side effects in adults who received doxycycline for at least a month.

Methodology: This retrospective descriptive study included adults who received oral doxycycline for at least one month between 2016 and 2018. The primary outcome was the frequency of esophagitis. The secondary outcomes were frequency of and discontinuation due to GI adverse effects.

Results: A total of 189 subjects were included with a median age of 32 years. The median duration of doxycycline use was 44 days (interquartile range 30-60). Twelve patients (6.3%) reported having GI adverse effects resulting in doxycycline discontinuation in five of them (2.6%), and three patients (1.6%) had esophagitis. The incidence of GI adverse effects was significantly higher in patients who were ≥ 50 years than < 50 years old (8/50 vs. 4/139; p = 0.003) and in those who received a daily dose of 200 mg than 100 mg (12/93 vs. 0/96; p < 0.001).

Conclusions: GI adverse events, including esophagitis, are not rare with long-term use of oral doxycycline, particularly in older age and a higher dose of 200 mg/day. Future large and randomized studies are needed to compare the efficacy and safety of different doxycycline doses.