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The Effect of Ingestion of Ferrous Sulfate on the Absorption of Oral Methotrexate in Patients with Rheumatoid Arthritis
SEAN F. HAMILTON, NORMAN R.C. CAMPBELL, MOHAMEDTAKI KARA, JOCELYN WATSON, and MARGARET CONNORS
ABSTRACT.
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 µmoles compared to 7.65 µmoles 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. (J Rheumatol 2003;30:1948-50) Key Indexing Terms:
RHEUMATOID ARTHRITIS
From the Division of Rheumatology, Memorial University of Newfoundland, St. John's, Newfoundland; Departments of Medicine, Pharmacology and Therapeutics, University of Calgary, Calgary, Alberta; School of Pharmacy, Memorial University of Newfoundland; Patient Research Center, Health Care Corporation of St. John's, St. John's, Newfoundland, Canada. Supported by the Research and Development Fund, Faculty of Medicine, Memorial University of Newfoundland. S.F. Hamilton, MD, FRCPC, Associate Professor of Medicine, Discipline of Medicine, Division of Rheumatology, Memorial University of Newfoundland; N.R.C. Campbell, FRCPC, Professor of Medicine, Departments of Medicine, Pharmacology and Therapeutics, University of Calgary; M. Kara, BPharm, PhD, Associate Professor of Pharmacy; M. Connors, MSc, Pharmacy Laboratory Instructor, Memorial University of Newfoundland School of Pharmacy; J. Watson, BN, Patient Research Center, Health Care Corporation of St. John's. Address reprint requests to Dr. S.F. Hamilton, St. Clare's Mercy Hospital, St. John's, Newfoundland A1C 5B8, Canada. Submitted October 4, 2002; revision accepted January 23, 2003. |