DMARDs
Exam Tips
- In UK exams, explicitly state that methotrexate is taken once weekly and should be co-prescribed with folic acid on a different day.
- For monitoring questions, mention both absolute thresholds and trend changes (for example progressive fall in WBC or rise in ALT).
- If a patient on DMARDs is acutely unwell with fever or breathlessness, prioritise sepsis/pulmonary toxicity assessment and seek urgent specialist advice about temporary treatment interruption.
- Vaccination point is high yield: inactivated vaccines are encouraged; live vaccines generally avoided while immunosuppressed unless specialist-directed.
- Shared-care model is commonly tested: initiation in secondary care, with possible GP prescribing/monitoring once stable under local protocol.
Definition
Disease-modifying anti-rheumatic drugs (DMARDs) are immunomodulatory or immunosuppressive medicines used to reduce inflammatory disease activity and prevent long-term structural damage, especially in rheumatoid arthritis and related immune-mediated conditions. They include conventional synthetic, biologic, and targeted synthetic agents, and they require structured blood and clinical monitoring because serious toxicity and infection can occur even when patients initially feel well.
Pathophysiology
Autoimmune inflammatory diseases are driven by dysregulated innate and adaptive immune pathways (including TNF, IL-6/IL-17 axes, T-cell co-stimulation, B-cell activation, and JAK-STAT signalling), causing persistent synovitis, cytokine release, and tissue damage (for example pannus-mediated cartilage and bone erosion in rheumatoid arthritis). Conventional DMARDs (for example methotrexate, sulfasalazine, leflunomide, hydroxychloroquine, azathioprine) dampen immune-cell proliferation or mediator production more broadly, while biologics and targeted synthetic DMARDs block specific cytokines/cells/signalling proteins and therefore often act faster (typically within weeks). Toxicity mechanisms include marrow suppression, hepatotoxicity, nephrotoxicity, drug-induced lung injury, and infection susceptibility due to immune suppression. See standard rheumatology pathway figures showing cytokine targets and pannus formation (for example Kumar & Clark, Rheumatology chapter figures).
Risk Factors
- Older age and frailty
- Renal impairment (higher risk of drug accumulation and toxicity)
- Pre-existing liver disease or excess alcohol intake
- Baseline cytopenias or low albumin
- Pre-existing interstitial lung disease/chronic lung disease (relevant for methotrexate pneumonitis differential)
- Intercurrent sepsis or acute illness with dehydration
- Polypharmacy and interacting drugs (for example trimethoprim with methotrexate)
- Lack of vaccination or high infectious exposure risk
- TPMT deficiency/low activity before azathioprine
Clinical Features
Symptoms
- Nausea, abdominal pain, diarrhoea, or oral ulceration
- Fatigue, recurrent infections, sore throat, fever, or bruising (possible myelosuppression/infection)
- Breathlessness or dry cough (possible pulmonary toxicity, including methotrexate pneumonitis)
- Rash, pruritus, or alopecia
- Visual disturbance (hydroxychloroquine retinal toxicity warning symptoms)
- Peripheral neuropathic symptoms (numbness/tingling)
Signs
- Pallor, petechiae, ecchymoses, or signs of sepsis
- Jaundice or right upper quadrant tenderness suggesting hepatotoxicity
- Reduced oxygen saturation, fine crackles, or respiratory distress
- Active synovitis if inflammatory disease remains uncontrolled
- Weight loss or cachexia in severe chronic inflammation
Investigations
Management
Lifestyle Modifications
- Shared-care education: give written safety advice, monitoring schedule, and clear contact route for urgent toxicity symptoms.
- Vaccination optimisation: annual influenza, pneumococcal, and COVID-19 vaccines; ideally update before starting treatment.
- Avoid live vaccines while immunosuppressed unless specialist advice confirms safety.
- Infection avoidance counselling, including urgent advice after chickenpox/shingles exposure.
- Alcohol moderation and adherence support for blood-test monitoring.
Pharmacological Treatment
Conventional synthetic DMARDs (csDMARDs)
- Methotrexate 7.5 mg once weekly PO/SC initially, titrated (commonly up to 20-25 mg once weekly) + folic acid 5 mg once weekly on a different day
- Sulfasalazine 500 mg daily then increased gradually to 1 g twice daily (usual range up to 2-3 g/day)
- Hydroxychloroquine 200-400 mg daily (keep within recommended mg/kg limits to reduce retinal risk)
- Leflunomide 10-20 mg once daily
- Azathioprine typically 1-3 mg/kg/day in divided doses after TPMT assessment
Usually initiated in secondary care; methotrexate must be prescribed as ONCE WEEKLY only (major safety point). Contraindications/cautions include pregnancy for methotrexate and leflunomide (teratogenic), significant hepatic disease, severe cytopenia, severe infection, and important drug interactions (for example trimethoprim with methotrexate).
Biologic DMARDs (bDMARDs)
- Adalimumab 40 mg SC every other week
- Etanercept 50 mg SC once weekly
- Infliximab 3 mg/kg IV at weeks 0, 2, 6 then every 8 weeks
- Rituximab 1 g IV, repeated after 2 weeks (with specialist protocol)
Used when disease remains active despite csDMARDs or in specific indications. Screen for TB/hepatitis before treatment; avoid in active serious infection; monitor for infusion/injection reactions and opportunistic infection.
Targeted synthetic DMARDs (tsDMARDs)
- Tofacitinib 5 mg twice daily
- Baricitinib 4 mg once daily (dose reductions in renal impairment/older patients per SPC)
- Apremilast 30 mg twice daily after dose titration
Rapid onset compared with many csDMARDs; check interaction profile and infection risk. JAK inhibitors require careful VTE/cardiovascular/malignancy risk assessment in line with current MHRA/BNF safety advice.
Complications
- Serious infection, including opportunistic infection and sepsis
- Myelosuppression (neutropenia, anaemia, thrombocytopenia)
- Drug-induced liver injury
- Renal function deterioration
- Pulmonary toxicity (for example methotrexate pneumonitis/interstitial changes)
- Hypersensitivity reactions and severe rash
- Retinal toxicity with hydroxychloroquine
- Disease flare and progressive joint/organ damage if therapy is interrupted or ineffective
Prognosis
With early specialist initiation, tight monitoring, and treat-to-target escalation, many patients achieve low disease activity or remission and reduced long-term disability. Prognosis worsens with delayed treatment, poor adherence, recurrent infection forcing treatment interruption, or unrecognised toxicity. Regular review of blood trends and rapid response to red-flag symptoms improves safety outcomes.
Sources & References
✅NICE Guidelines(1)
- DMARDs[overview]