Iron poisoning is one of the most potentially serious forms of poisoning seen in the UK by the NPIS. There is little data available on the most appropriate dose and duration of treatment with the antidote desferrioxamine (DFO). The NPIS, therefore, set up a prospective study collecting data on iron poisoning cases presenting to hospital between 1 February 2014 and 17 January 2016. Inclusion criteria were: ingestion of a potentially toxic dose of iron (≥20 mg/kg), symptomatic patient, raised serum iron concentration (greater than or ≥55 micromoles/L), or patient being treated with DFO.
Over the period, NPIS received 1,210 calls relating to iron exposures, the majority (502, 54.5%) from hospitals. Following exclusions (skin/eye contact; exposure to rust, fertiliser, moss killer, weed killer or slug bait; asymptomatic late presentation; and patients who were followed up but did not meet inclusion criteria), there were 397 patients in hospital who met the criteria for follow-up, including 16 patients aged 15 or younger and four patients under five years.
At the time of the enquiry, most patients were asymptomatic or had minor features (36.0% and 50.4%, respectively). Moderate and severe features were present in only 10.1% and 2.5% of patients, respectively. Features were not known for 1.1% of cases. The maximum poisoning severity score for each patient was recorded as follows: asymptomatic 22.2%; minor features 58.9%; moderate features 13.4% and severe features 2.8%. Features were not known in 1.6% of cases. At follow-up, four deaths were recorded, although none were considered likely to be caused by the iron content of the overdose; three were mixed overdoses which included cardiovascular agents in unknown amounts and the fourth was an elderly patient with pre-existing chronic heart failure.
Forty eight patients received DFO following iron overdose and one patient was discussed with the NPIS following an overdose of DFO in error during the treatment of thalassemia. In 28 of these cases (57.1%), iron was ingested alone. At the time of presentation, the patients were: asymptomatic 12.2%; minor features 49.0%; moderate features: 26.5% and severe features 8.16%. Features were not known for 4.1% of cases.
The total dose/kg of DFO administered was known for 15 (30.6%) patients and could be estimated for a further three patients (80 mg/kg, 80 mg/kg, >75 mg/kg). Median total dose was 70 mg/kg (IQR 41 to 79), with a maximum dose of 260 mg/kg. Four patients received doses greater than the current recommendation before reassessment (83, 85, 90, and 260 mg/kg), which is 80 mg/kg but no adverse events were recorded. The patient receiving the highest dose was an 18-year-old man with a blood iron concentration of 79 µmol/L at 3.5 h who received 15 mg/kg/h for 17.5 hours.
This study showed that enquiries about iron poisoning are an important part of NPIS’s workload but that fewer cases are severe and relatively few patients need antidotes (compared for example with the 40% to 50% of paracetamol poisoned patients who receive the antidote acetylcysteine).
Information from the NPIS Annual Report 2015/16.
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