Oral methotrexate overdose

Balit, C.R., Daly, F.F.S., Little, M., and Murray, L. (2006) Oral methotrexate overdose. Clinical Toxicology, 44 (4). 12. pp. 411-412.

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Background: Methotrexate (MTX) is a folate antagonist used in the management of rheumatoid arthritis and as an antimetabolite in cancer chemotherapy. MTX toxicity following parenteral administration is well described, predictable on the basis of timed serum concentrations, and preventable by the administration of folinic acid. Although MTX toxicity has never been reported fol- lowing single oral overdose, many authorities recommend treatment with folinic acid. The objective of this study was to describe the clinical course following acute MTX ingestion and the utilization of MTX levels in refining the risk assessment. Methods: Following institution of a standard management protocol for acute MTX ingestion at the NSW Poisons information Centre, data was prospectively collected on all acute intentional or unintentional ingestions of methotrexate reported to the centre. The proto- col withheld immediate administration of folinic acid for ingestion of < 500 mg in adults or < 5 mg/kg in children, provided results of timed plasma MTX concentrations could be obtained within 24 hours. Follow-up full blood count was recommended for all patients at 7 days. Results: Between March 2004 and November 2005, 13 patients were reported to the centre: three paedi- atric unintentional and 9 adult intentional ingestions. One patient was lost to follow-up. Accidental ingestions: doses ranged from 2.5–12.5 mg. No child developed symptoms or required any treatment. Intentional ingestions: median ingested dose was 300 mg (Range 40–1000 mg). Table 1 below demonstrates the MTX levels for the intentional ingestions. No patient demonstrated any symptoms and no patient had a serum MTX level greater than that predicting toxicity (5 micromoles/L at 6 hours post-ingestion). Many patients were given folinic acid by the treating physician despite PIC recommendations. Three patients had follow-up full blood counts at 7 days post ingestion; all were normal. Further cases are being recruited. Conclusions: Single acute overdose of MTX does not result in serum MTX concentrations associated with toxicity. It is likely that folinic acid therapy can be safely withheld for ingestions of less than 500 mg in adults.

Item ID: 38651
Item Type: Article (Abstract)
ISSN: 1556-9519
Additional Information:

Abstracts of the European Association of Poisons Centres and Clinical Toxicologists XXVI International Congress

Date Deposited: 08 Feb 2017 00:02
FoR Codes: 11 MEDICAL AND HEALTH SCIENCES > 1115 Pharmacology and Pharmaceutical Sciences > 111506 Toxicology (incl Clinical Toxicology) @ 100%
SEO Codes: 92 HEALTH > 9299 Other Health > 929999 Health not elsewhere classified @ 100%
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