Esomeprazole induced galactorrhea: a novel side effect

Proton pump inhibitors (PPIs) are one of the most frequently prescribed medications across the globe. Esomeprazole is the S-isomer of omeprazole, and it is currently the most widely prescribed PPI. The safety profile of esomeprazole is extremely favorable with only minor side effects, like headache and diarrhea, that are encountered in day to day practice. We report a case of a young female with symptoms of gastroesophageal reflux disease who developed galactorrhea after starting esomeprazole therapy. Resolution of galactorrhea after stopping the drug and self-rechallenge by the patient herself with reappearance of galactorrhea confirmed the culprit to be esomeprazole only. We postulate that esomeprazole may have a mild inhibitory effect on CYP3A4, which leads to decreased metabolism of estrogen, thereby increasing serum estrogen levels. Estrogen causes stimulation and production of prolactin release, which results in development of galactorrhea. This is the first case of esomeprazole induced galactorrhea, to the best of our knowledge.