Possible aescin–rowachol interaction presenting as acute watery diarrhea: a case report and proposed mechanism

Background Drug-induced acute diarrhea is a common adverse effect, but its occurrence due to interaction between herbal medicinal products is rarely documented. We describe a case of acute watery diarrhea developed shortly after Reparil ® (aescin) was added to chronic Rowachol ® (terpene-based) therapy in a patient with cholelithiasis, raising the possibility of a drug interaction. Case presentation A male patient in his thirties, who had been receiving Rowachol ® for symptomatic cholelithiasis for three months, developed watery acute diarrhea within hours of initiating aescin (for acute hemorrhoidal attack). Vital signs were within normal limits. Routine stool testing was unremarkable except for the presence of mucus, and fecal calprotectin was within normal limits. Fecal bile acids were not measured. Given the suspicion of a drug interaction, the Drug Interaction Probability Scale (DIPS) was applied, yielding a score of 4, corresponding to a possible interaction. Symptomatic treatment was provided, and the diarrhea resolved after aescin was discontinued, while Rowachol ® was continued unchanged. The following day, Daflon ® (diosmin/hesperidin) was initiated, and no further gastrointestinal complaints were reported. Conclusions This case describes acute watery diarrhea shortly after the addition of aescin to chronic Rowachol therapy, with rapid resolution following aescin withdrawal. The temporal relationship and DIPS assessment support a possible interaction; however, causality and the proposed bile-acid-mediated mechanism remain unconfirmed. Further pharmacovigilance observations are required to determine whether this represents a reproducible and clinically relevant interaction.