Irbesartan/lubiprostone Hypovolaemic hyponatraemia and watery diarrhoea: case report A 72-year-old man developed hypovolaemic hyponatraemia and watery diarrhoea during treatment with lubiprostone and exacerbation of hypovolaemic hyponatraemia during treatment with irbesartan [not all routes and durations of treatments to reactions onsets stated]. The man, who had trauma, underwent left nephrectomy and received blood transfusion at the age of 21 years. Since 35 years of age, he had glomerulonephritis and chronic hepatitis. At 69 years of age, he visited the hospital due with high BP, serum creatinine and proteinuria. Initially, he received treatment with irbesartan 100mg. Although his BP was controlled by irbesartan, the proteinuria persisted. He also had hepatitis C and had received asunaprevir and daclatasvir. Six months later, he recovered from hepatitis C, but his proteinuria still persisted. Later, at 71 years of age, he developed renal anaemia and received methoxy polyethylene glycol epoetin beta [epoetin beta pegol]. At 72 years of age, a decrease in his serum sodium concentration was noted. Although his abdominal CT revealed no ascites, he was instructed to reduce water intake to less than 1 L/day. A week prior to his admission, he received methoxy polyethylene glycol epoetin beta and complained constipation, for which he was administered bisacodyl. He was unsatisfied despite having bowel movement. Five days afterwards, he presented to the clinic and was administered oral lubiprostone 24µg. This medication induced frequent watery diarrhoea. On day 1 of admission, bowel movement was 7/day and his weight was 68.4kg. Next morning, he visited the hospital (current presentation) because of consciousness disturbance. Physical examination revealed dehydration and laboratory data showed hypovolaemic hyponatremia. Although the man was infused with sodium chloride [saline], his consciousness did not recover. Syndrome of inappropriate secretion of antidiuretic hormone was doubtful, as acute reductions in his body weight suggested dehydration and plasma osmolality was higher than urine osmolality at the time of admission. After hospitalisation, therapy with lubiprostone was stopped, and to correct electrolyte disturbance and dehydration, he was initiated on sodium chloride. In the morning of day 3 of admission, he regained consciousness with no neurological sequels. On day 5 of admission, no diarrhoea was observed. On day 6, sodium chloride was discontinued, but only by day 7, his serum sodium concentration recovered. On day 7, bowel movement was 1 /day and his weight was 72.3kg. Subsequently, he was discharged. As he did not agree, therapy with lubiprostone was not recommenced.
