Endocrine Abstracts

Tolvaptan (a V2 receptor antagonist) is licensed for correction of hyponatraemia in patients with SIADH at an initial dose of 15 mg od. Data in oncology patients with SIADH suggest 7.5 mg can safely and effectively increase sodium levels where 15 mg can on occasion lead to too rapid a correction. Recommendations suggest a repeat sodium taken at 4–6 h. We retrospectively assessed the safety and efficacy of intermittent out-patient dosing with 7.5 mg tolvaptan. Pharmacy records and casenotes were interrogated to find all patients given out-patient prescriptions for tolvaptan between April 12 and January 15. 15 doses were administered in a total of four patients (three men, one female; mean age 63 years). All had biochemically confirmed SIADH secondary to small cell lung cancer, had received fluid restriction and demeclocycline prior to tolvaptan as inpatients and were euvolaemic. All patients were also receiving therapy for the primary malignancy concurrently. Indications for treatment were symptomatic hyponatraemia or downward trending sodium. Mean pre-out-patient tolvaptan sodium was 126 mmol/l (range 122–128). Mean first sodium post-tolvaptan was 133.6 mmol/l (range 128–139), with mean increase 7.6 mmol/l. Timing of repeat sodium ranged from 6 h to 6 days. On eight occasions a repeat sodium was done at 6 h – mean sodium rose from 125.75 (122–128) to 132 mmol/l (128–137). The largest rise was 10 mmol/l at 6 h. No adverse events were encountered. One patient died due to progressive malignancy.