Sulfasalazine
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Dosing and administration[3]
Oral enteric-coated (EN) tablets, swallowed whole with food. Start low and titrate weekly to reduce gastrointestinal intolerance.
| Indication | Starting dose | Titration and maximum |
|---|---|---|
| Rheumatoid arthritis and psoriatic arthritis | Start 500 mg daily and increase by 500 mg weekly to a usual maintenance of 2 g/day in 2 divided doses. | May increase to 3 g/day in divided doses if response is inadequate after about 12 weeks; monitor more closely above 2 g/day. |
Onset. Onset over about 6 to 12 weeks.
Renal adjustment. Use with caution in renal impairment; maintain adequate hydration.
Hepatic. Use with caution in hepatic impairment; monitor liver function.
Monitoring
- CBC and liver function at baseline, then every 2 to 4 weeks for the first 3 months, then periodically.
- Watch for myelosuppression (including agranulocytosis), hepatotoxicity, and hypersensitivity reactions.
- Consider G6PD status (hemolysis risk).
Contraindications
- Hypersensitivity to sulfonamides or salicylates.
- Porphyria.
- Intestinal or urinary tract obstruction.
Key interactions
- Reduces folate absorption (folate supplementation may be needed).
- Reduces digoxin absorption.
- Additive myelosuppression with other marrow-suppressing agents.
Clinical notes
Common side effects
Nausea, headache, and rash are common early and often dose-related; harmless orange discolouration of body fluids can occur. Cytopenias and transaminitis are less common. Not sourced on this draft.
Tests and monitoring
Baseline complete blood count, liver transaminases, and serum creatinine. On treatment, check CBC, transaminases, and creatinine every 2 to 4 weeks for the first 3 months, every 8 to 12 weeks from 3 to 6 months, and every 12 weeks beyond 6 months, testing more often after a dose increase. This is the ACR conventional-DMARD monitoring schedule, defined for rheumatoid arthritis.[1, 2]
Important cautions
Caution with sulfonamide or salicylate hypersensitivity and G6PD deficiency; reversible oligospermia can occur in men. Reproductive-health guidance is on the pregnancy record. To confirm from primary sources.
References
- Saag KG, Teng GG, Patkar NM, et al. American College of Rheumatology 2008 recommendations for the use of nonbiologic and biologic disease-modifying antirheumatic drugs in rheumatoid arthritis. Arthritis Rheum. 2008;59(6):762-784. doi:10.1002/art.23721 https://doi.org/10.1002/art.23721
- Singh JA, Saag KG, Bridges SL Jr, et al. 2015 American College of Rheumatology Guideline for the Treatment of Rheumatoid Arthritis. Arthritis Care Res. 2016;68(1):1-25. doi:10.1002/acr.22783 (published simultaneously in Arthritis & Rheumatology) https://doi.org/10.1002/acr.22783
- SALAZOPYRIN EN-tabs (sulfasalazine enteric-coated tablets) Product Monograph. Health Canada authorized product monograph. https://pdf.hres.ca/dpd_pm/00058401.PDF