Drug-induced haemolysis: another reason to be cautious with nitrofurantoin

In conjunction with BMJ Case Reports, DTB will feature occasional drug-related cases that are likely to be of interest to readers. These will include cases that involve recently marketed drugs for which there is limited knowledge of adverse effects and cases that highlight unusual reactions to drugs that have been marketed for several years. We report the case of a previously healthy woman in her 60s who presented to the emergency department with acute confusion, vomiting and fever. She was recently diagnosed with a urinary tract infection as an outpatient and had completed the fifth day of a 7-day course of treatment with nitrofurantoin. We maintained a wide differential diagnosis including infectious, metabolic, autoimmune and medication-related causes. She developed an acute normocytic anaemia in hospital with a haemoglobin drop from 121 g/L to 89 g/L. Further investigation revealed evidence of haemolysis with an elevated bilirubin, lactate dehydrogenase, reticulocyte count and decreased haptoglobin. She was worked up for both inherited and acquired causes of haemolysis and found to have glucose-6-phosphate dehydrogenase deficiency. Her presentation was thought to be secondary to nitrofurantoin-induced haemolysis and she recovered completely with conservative management through intravenous fluids and discontinuation of nitrofurantoin. Nitrofurantoin is recommended by both the Canadian and American Urological Association as a first-line antibiotic for uncomplicated urinary tract infections (UTIs),1 even though it only exerts bactericidal effects in the urine when reacting with susceptible bacteria at therapeutic doses.2 As a commonly prescribed antibiotic, clinicians should be aware of its broad side effect profile. Nitrofurantoin is frequently associated with nausea, vomiting, diarrhoea and loss of appetite.2 It has also been associated with severe adverse events such as pulmonary toxicity, hepatotoxicity and peripheral neuropathy. Haemolytic anaemia in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency is another possible side effect, which may be easily overlooked, …