Hyponatraemia, fever, vomiting, severe abdominal pain, and weight loss associated with omeprazole

Case report A 60-year-old Caucasian female was admitted to hospital on 29 December 2003 complaining of nausea, vomiting, anorexia, severe abdominal pain, and significant weight loss. [...]in the case reported by Landray et al, pyrexia, anaemia, and acute renal failure were present--but gastrointestinal symptoms or hyponatraemia did not feature.4 Hyponatraemia has been reported on at least eight occasions5,8 and there are three cases reported in the CARM database.6 Interestingly, Rosholm et al noted in a population study that omeprazole usage was associated with a lower median serum sodium concentration (difference 3 mmol/L), although they felt that this was not clinically relevant.9 The question arises whether this lady's adverse events were due to idiosyncrasy or prolonged exposure to a higher dose range of omeprazole. Whatever the mechanism (idiosyncrasy is perhaps the most likely), this patient appeared to have had a life-threatening complex of signs and symptoms (fever, hyponatraemia, vomiting, weight loss, and abdominal pain) associated with exposure to omeprazole--a combination of adverse effects not hitherto reported in association with this drug.