RT Journal Article SR Electronic T1 The effect of ingestion of ferrous sulfate on the absorption of oral methotrexate in patients with rheumatoid arthritis. JF The Journal of Rheumatology JO J Rheumatol FD The Journal of Rheumatology SP 1948 OP 1950 VO 30 IS 9 A1 Sean F Hamilton A1 Norman R c Campbell A1 Mohamedtaki Kara A1 Jocelyn Watson A1 Margaret Connors YR 2003 UL http://www.jrheum.org/content/30/9/1948.abstract AB OBJECTIVE: To investigate if ingestion of ferrous sulfate, 300 mg twice daily, will reduce the urinary excretion of unmetabolized methotrexate (MTX) in patients with rheumatoid arthritis (RA) who ingest 2 drugs concurrently, and determine if ferrous sulfate interferes with the absorption of oral MTX. METHODS: In this randomized double-blind placebo controlled crossover study, we compared the urinary excretion of unmetabolized MTX in 10 patients with RA who ingested 7.5 mg MTX as their weekly dose and took either ferrous sulfate 300 mg twice daily or placebo. RESULTS: Ten patients with RA taking 7.5 mg MTX orally once weekly had an average 24 h urine excretion of MTX (while taking 300 mg ferrous sulfate twice daily for one week) of 8.44 micromoles compared to 7.65 micromoles for patients taking placebo. The difference was not statistically significant (p = 0.50). CONCLUSION: Our results showed no less absorption of MTX for the placebo group compared to the group that took ferrous sulfate. These results do not support the hypothesis that ferrous sulfate interferes with the absorption of oral MTX.