Iatrogenic nephrogenic diabetes insipidus secondary to demeclocycline misuse


A Stevenson, K Gill, A Robbins, K Yoganathan, S A Qureshi, West Middlesex University Hospital


We present the case of an 84 year old male who was admitted to the acute medical ward following a fall and increasingly agitated behaviour. During a previous admission he was persistently hyponatraemic (ranging 119-130mmol/L) and diagnosed with SIADH of unknown aetiology. Fluid restriction failed to normalise his sodium so he was discharged on 300mg demeclocycline. Upon re-attendance he was found to be profoundly hypernatraemic (162mmol/L) with a GCS score of 7/15. Clinically he was profoundly hypovolaemic, but despite this he was passing 2-3 litres of dilute urine per day. He was hypernatraemic at 162mmol/L with a serum osmolality of 397mosm/kg (275-295mosm/kg), a urine osmolality of 408mosom/kg (50-1200mosm/kg) and urinary sodium of 36mmol and a significant acute kidney injury.


A diagnosis of diabetes insipidus was made secondary to inappropriate use of demeclocycline. He was managed with 5% dextrose replacement as well as intravenous antibiotics for sepsis. His sodium rose to 177mmol/L but given his poor baseline and co-morbidities it was decided he was not for escalation to intensive care or the high dependency unit. Unfortunately he remained persistently drowsy and he continued to pass 2-3 litres of dilute urine. His renal function did not improve, his sepsis failed to respond to antibiotics, so the decision was made to withdraw care and the patient passed away the following day.



Figure 1: Serum sodium. Black arrow demonstrates when discharged with demeclocycline. Red arrow shows when readmitted two weeks later.













Learning Points:

1.     This case highlights how inappropriate prescription and monitoring of demeclocycline can have serious adverse effects, in this case with severe, symptomatic hypernatraemic, volume depletion and acute kidney injury.

2.     Our case highlights how great care should be taken when commencing a patient on demeclocycline as it typically takes days to weeks to take effect. It should be reserved for persistent severe hyponatraemia, should be undertaken under specialist endocrine supervision and should be monitored regularly on an endocrine ward.