GPAtlas🧭 When to suspect toxicity (and the shared-care role)
Disease-modifying anti-rheumatic drugs (DMARDs) are specialist-initiated immunomodulators used in autoimmune and inflammatory disease:
• Rheumatoid arthritis
• Psoriatic arthritis
• Ankylosing spondylitis
• Systemic lupus erythematosus (SLE) and connective-tissue disease
• Vasculitis
• Juvenile idiopathic arthritis
• Psoriasis
• Inflammatory bowel disease
They control the disease process rather than just symptoms, but every one of them carries a risk of:
• Bone-marrow suppression
• Hepatotoxicity
• Infection
• Organ-specific toxicity (for some)
This is why structured monitoring is mandatory.
In primary care the GP almost always meets these drugs through a shared-care agreement: rheumatology (or dermatology/gastroenterology) initiates, stabilises and retains overall responsibility, then asks the GP to continue prescribing and to perform the agreed blood monitoring.
The single golden rule of that contract is simple – no satisfactory, up-to-date monitoring means no prescription. Never issue a repeat if the bloods are overdue, missing, or abnormal.
The two core GP skills are therefore safe shared-care monitoring and recognising toxicity.
Suspect an adverse effect whenever a patient on a DMARD presents with:
• Infection
• Signs of marrow suppression (unexplained bruising, bleeding, sore throat, mouth ulcers)
• Liver toxicity (jaundice, nausea)
• Respiratory symptoms (new cough or breathlessness)
| DMARD | Routine bloods (per local protocol) | Key toxicities & cautions |
|---|---|---|
| Methotrexate | FBC, U&E, LFT | • Myelosuppression, hepatotoxicity, pneumonitis. Once weekly • Co-prescribe folic acid • Never with trimethoprim/co-trimoxazole |
| Sulfasalazine | FBC, LFT | • Myelosuppression (esp. first months), hepatitis, rash • Not significantly immunosuppressive |
| Hydroxychloroquine | • No routine bloods • Annual eye review |
Long-term retinopathy. Not significantly immunosuppressive. |
| Leflunomide | FBC, LFT, BP, weight | • Hepatotoxicity, hypertension, diarrhoea/weight loss • Long half-life – needs cholestyramine washout |
| Azathioprine | • FBC, LFT • Check thiopurine methyltransferase (TPMT) before starting |
• Myelosuppression • Never full-dose with allopurinol (life-threatening toxicity) |
| Mycophenolate | FBC, LFT | • Myelosuppression, gastrointestinal (GI) upset • Strongly teratogenic (men and women) |
Source: BSR 2025 csDMARD guideline · MHRA
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