NutriStack
Sulfasalazine and Vitamin B9, a synergy.
Sulfasalazine can reduce folate absorption and inhibit folate-dependent enzymes. Most people do not develop severe deficiency, but risk rises with long-term therapy, low dietary folate intake, pregnancy, anemia, or other antifolate medicines. Vitamin B9 supplementation helps offset this depletion risk during sulfasalazine therapy.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
Same shape as the other 1,729 pairs in the public database.
From the interaction database
What the row says.
Every entry follows the same shape: what is happening, the mechanism, the recommendation, and the primary literature.
At a glance
- Substances
- Sulfasalazine and Vitamin B9
- Pair type
- Synergy
- Evidence (highest tier)
- Moderate
- Source citations
- 3 sources
- Stack Score effect
- +2 to your Stack Score (per scored synergy row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Synergy · Moderate evidence
Synergy
What is happening. Sulfasalazine can reduce folate absorption and inhibit folate-dependent enzymes. Most people do not develop severe deficiency, but risk rises with long-term therapy, low dietary folate intake, pregnancy, anemia, or other antifolate medicines. Vitamin B9 supplementation helps offset this depletion risk during sulfasalazine therapy.
Mechanism. Sulfasalazine competitively inhibits intestinal folate transport and can inhibit folate-dependent enzymes, including dihydrofolate reductase-related pathways. Supplemental Vitamin B9 replenishes folate pools needed for one-carbon metabolism and blood-cell production.
Recommendation. Ask your prescriber whether you should take daily folate while using sulfasalazine, especially if you are pregnant, planning pregnancy, anemic, or taking another antifolate drug. Do not use folate to ignore new mouth sores, severe fatigue, bruising, or worsening anemia; those symptoms need lab review.
Sources (3)
- Halsted CH, Gandhi G, Tamura T. Sulfasalazine inhibits the absorption of folates in ulcerative colitis. N Engl J Med. 1981;305(25):1513-1517. PMID 6117796
- Selhub J, Dhar GJ, Rosenberg IH. Inhibition of folate enzymes by sulfasalazine. J Clin Invest. 1978;61(1):221-224. PMID 22555
- Schoeman M, Bezuidenhout DJ. Folate levels in patients with ulcerative colitis receiving sulphasalazine. S Afr Med J. 1984;66(11):415. PMID 6148790
Stack Score
How this pair moves the number.
Effect on the composite score
If both Sulfasalazine and Vitamin B9 are in the same stack, this pair applies +2 to your Stack Score (per scored synergy row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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