💊 Sulfasalazine

Sulfasalazine is an aminosalicylate derivative, often classified as a disease-modifying antirheumatic drug (DMARD) or an anti-inflammatory agent.

It is a prodrug, metabolised in the colon by bacteria into sulfapyridine and 5-aminosalicylic acid (5-ASA). 5-ASA exerts local anti-inflammatory effects by inhibiting prostaglandin and leukotriene synthesis, and scavenging free radicals. Sulfapyridine is thought to be responsible for systemic effects in rheumatic conditions.

In the UK, sulfasalazine is primarily used for inflammatory bowel disease (IBD), particularly ulcerative colitis, to induce and maintain remission. It is also a common first-line DMARD for rheumatoid arthritis and other inflammatory arthropathies like psoriatic arthritis.

Absolute contraindications include hypersensitivity to salicylates, sulfonamides, or sulfasalazine itself. It is also contraindicated in porphyria, severe renal or hepatic impairment, and in children under two years old due to the risk of kernicterus.

Common side effects include nausea, vomiting, abdominal pain, headache, and skin rashes. More serious but less common adverse effects include bone marrow suppression (leukopenia, thrombocytopenia, agranulocytosis), hepatotoxicity, and hypersensitivity reactions (e.g., Stevens-Johnson syndrome).

Baseline and regular monitoring of full blood count (FBC), liver function tests (LFTs), and renal function tests (U&Es) are essential. FBC and LFTs should be checked frequently in the initial months of treatment, then less often once stable.

Always check for allergies to sulfonamides or salicylates before prescribing. Counsel patients on the importance of reporting fever, sore throat, or unexplained bruising/bleeding immediately. Advise patients that urine and contact lenses may turn orange/yellow.

A classic DMARD and IBD drug, remember its prodrug nature and the two active metabolites. High yield for its broad range of side effects, especially haematological and hepatic. Often used when methotrexate is contraindicated or not tolerated in rheumatology.

SBAs often test recognition of its use in both IBD and rheumatoid arthritis. Questions may focus on key adverse effects like bone marrow suppression or hypersensitivity reactions, and the importance of regular blood monitoring. Another common theme is its contraindication in sulfa allergy.