DMARDs (Disease-Modifying Anti-Rheumatic Drugs)

🔍 When to Suspect

A patient on a disease-modifying anti-rheumatic drug (DMARD) presents with new signs of infection (e.g., sore throat, fever), bone marrow suppression (e.g., bruising), or liver/lung toxicity

From the full topic in The Ocean Library: DMARDs (Disease-Modifying Anti-Rheumatic Drugs)

🧭 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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