Reactions Weekly | 2021
Esomeprazole/fluconazole interaction
Abstract
Hypokalaemia, hypocalcaemia, hypomagnesaemia: case report A 65-year-old man developed hypokalaemia, hypocalcaemia and hypomagnesaemia following pharmacokinetic interaction of fluconazole for oropharyngeal infection and esomeprazole that led to esomeprazole intoxication [not all dosages and indications stated; routes and duration of treatments to reaction onsets not stated]. The man presented to the emergency department with diffuse abdominal pain, vomiting and general weakness experienced for several days. He had a medical history of pulmonary embolism. Two months ago, he had undergone a repeat autologous stem cell transplantation due to recurrent multiple myeloma. His ongoing medications included fluconazole, rivaroxaban and esomeprazole. He was recently prescribed fluconazole for an oropharyngeal infection 10 days prior to current presentation. Upon admission, he was not able to converse. His wife reported that his epigastric pain developed 5 days earlier along with vomiting for 2 days. He also appeared disoriented and moderately ill. Physical examination with deep palpation revealed mild diffuse abdominal tenderness. Neurological analysis revealed tremor, confusion and aphasia. His ECG findings reported a right bundle branch block and a prolonged QT-interval. A point-of-care blood gas and blood analysis indicated metabolic alkalosis, hypokalaemia, hypomagnesaemia and hypocalcaemia. A working diagnosis of severe hypocalcaemia was considered with severe neurologic and GI symptoms. The man was treated with calcium gluconate. Following calcium supplementation, his confusion, nausea and aphasia resolved within minutes and a normal QT-interval was observed. Urinary potassium excretion was high and magnesium excretion was low. Profuse vomiting had reportedly worsened the electrolyte disturbances. A significant rise in plasma concentrations of esomeprazole was also seen. Thus, he was diagnosed with hypokalaemia, secondary hypocalcaemia and severe hypomagnesaemia secondary to pharmacokinetic interaction of esomeprazole and fluconazole. The interaction of esomeprazole and fluconazole led to increased plasma levels of esomeprazole causing its intoxication. He was admitted and initiated on calcium, potassium and magnesium supplementation. His therapy with esomeprazole was stopped and he was discharged after 3 days in a good condition.