Preliminary evidence shows that folic acid fortification of the food supply is associated with higher methotrexate dosing in patients with rheumatoid arthritis.
BACKGROUND
Fortification of the diet with folate has been used in the United States since 1997 to prevent neural tube defects in newborn babies. However, an increase in dietary folate intake could theoretically reduce the effectiveness of the anti-folate medication, methotrexate (MTX) in treating rheumatoid arthritis (RA) and other inflammatory diseases.


OBJECTIVE
To investigate whether dietary fortification with folic acid interferes with MTX function in patients with RA.


METHODS
We computed MTX dose per patient per year for the years 1988 to 1999 and plotted these against time, comparing the overall mean MTX dose before and after 1997, when dietary fortification with folic acid was instituted in the USA. Thirty-six subjects met eligibility criteria.


RESULTS
Mean annual MTX dose was stable between 1988 and 1996 (12.4 +/- 4.0mg), but then rose linearly from 1997 to 1999 (16.6 +/- 5.1 mg, p < 0.001).


CONCLUSIONS
This preliminary study suggests that folic acid supplementation may contribute to higher MTX dosing in patients with RA.
Arabelovic
Senada
S
US Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, Boston, Massachusetts 02111, USA.
Sam
Gina
G
Dallal
Gerard E
GE
Jacques
Paul F
PF
Selhub
Jacob
J
Rosenberg
Irwin H
IH
Roubenoff
Ronenn
R
D000328:Adult; D000368:Aged; D018501:Antirheumatic Agents / Q000627:therapeutic use*; D001172:Arthritis, Rheumatoid / Q000188:drug therapy*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage* / Q000009:adverse effects; D005523:Food Supply; D005527:Food, Fortified / Q000009:adverse effects; D006801:Humans; D008297:Male; D008727:Methotrexate / Q000627:therapeutic use*; D008875:Middle Aged; D012189:Retrospective Studies
D018501:Antirheumatic Agents; D005492:Folic Acid; D008727:Methotrexate