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Aminosalicylate / Disease-Modifying Antirheumatic Drug (DMARD) Pregnancy: Compatible — widely used in IBD and RA during pregnancy. Supplement folic acid 5mg/day. Avoid in neonates (risk of haemolytic anaemia and neonatal jaundice from sulphapyridine — stop at 36 weeks or switch to mesalazine).

Sulfasalazine

Brand names: Salazopyrin, Salazopyrin EN-Tabs

Adult dose

Dose: Ulcerative colitis — active disease: 1–2g QDS until remission. Maintenance: 500mg–1g QDS. Crohn's disease (colonic): 1–2g QDS. Rheumatoid arthritis: 500mg OD, increasing by 500mg weekly to 2–3g/day in divided doses.
Route: Oral
Frequency: Four times daily (IBD); two to three times daily (RA)
Max: 4g/day (IBD active phase); 3g/day (RA)
Contains sulphapyridine + 5-aminosalicylic acid. Check for sulphonamide allergy — contraindicated if allergic. EN-Tabs (enteric-coated) preferred to reduce GI side effects. Take with food. TPMT testing not required (unlike azathioprine) but monitor FBC.

Paediatric dose

Dose: 10 mg/kg
Route: Oral
Frequency: Three to four times daily
Max: 40mg/kg/day or 4g/day
BNF for Children: ≥2 years (specialist supervision): UC — initially 10–15mg/kg TDS–QDS (max 40mg/kg/day). RA (≥5 years, specialist): initially 5mg/kg OD, increasing to 10–15mg/kg BD (max 2g/day). Source: BNF for Children 2024.

Dose adjustments

Renal

Avoid in severe renal impairment (risk of crystalluria, nephrotoxicity). Reduce dose in moderate impairment.

Hepatic

Use with caution — hepatotoxicity risk; avoid in severe hepatic impairment.

Paediatric weight-based calculator

BNF for Children: ≥2 years (specialist supervision): UC — initially 10–15mg/kg TDS–QDS (max 40mg/kg/day). RA (≥5 years, specialist): initially 5mg/kg OD, increasing to 10–15mg/kg BD (max 2g/day). Source: BNF for Children 2024.

Clinical pearls

  • Orange urine/tears: warn patients — harmless sulphapyridine metabolite. Can stain soft contact lenses permanently.
  • Male infertility: causes reversible oligospermia in up to 70% of men — reverses within 3 months of stopping. Counsel male patients planning fatherhood.
  • Folic acid supplementation: 5mg/day recommended (folate antagonism) — important especially in women of childbearing age.
  • EN-Tabs (enteric-coated): significantly reduce GI side effects (nausea) — prescribe enteric-coated formulation in preference to plain tablets.

Contraindications

  • Sulphonamide hypersensitivity
  • Salicylate hypersensitivity
  • Severe renal or hepatic impairment
  • Porphyria
  • Infants <2 years

Side effects

  • Nausea, vomiting, dyspepsia (most common — use EN-Tabs to reduce)
  • Headache, dizziness
  • Myelosuppression (leukopenia, thrombocytopenia)
  • Hepatotoxicity (LFT elevation)
  • Orange discolouration of urine and tears (harmless — sulphapyridine metabolites)
  • Male infertility (reversible oligospermia — dose-dependent)
  • Hypersensitivity reactions (rash, Stevens-Johnson syndrome — rare)

Interactions

  • Azathioprine / mercaptopurine: inhibits TPMT enzyme — increased thiopurine toxicity risk
  • Methotrexate: increased methotrexate levels (folate antagonism) — monitor toxicity
  • Digoxin: reduced absorption
  • Folic acid: reduced absorption — supplement folic acid 5mg/day during treatment

Monitoring

  • FBC (baseline, then every 2 weeks for first 3 months, then every 3 months)
  • LFTs (same schedule as FBC)
  • Renal function (annually)
  • Symptoms of IBD or RA

Reference: BNFc; BNF 90; BSG UC Guidelines 2019; NICE NG130 IBD; NICE NG100 RA. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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