Disease-Modifying Antirheumatic Drugs

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DMARDs Overview - RheumaRiders Kickoff

  • DMARDs: Disease-Modifying Antirheumatic Drugs; aim to alter the underlying rheumatic disease process.
  • Goals of Therapy:
    • Achieve remission or low disease activity.
    • Prevent structural joint damage & long-term disability.
    • Improve Quality of Life (QoL).
  • General Principles:
    • Early diagnosis and prompt initiation.
    • Treat-to-target strategy.
    • Regular monitoring for efficacy and adverse effects.
  • Broad Classification:
    • csDMARDs (Conventional Synthetic)
    • bDMARDs (Biologic: original & biosimilars)
    • tsDMARDs (Targeted Synthetic) DMARD Classifications and FDA-Approved Drugs for RA

⭐ Methotrexate is the cornerstone DMARD for most Rheumatoid Arthritis patients, often initiated first-line unless contraindicated.

csDMARDs - Old Guard Allies

Methotrexate structure and mechanism

  • Methotrexate (MTX): 📌 'Mother Of All DMARDs'
    • MoA: Inhibits DHFR, AICAR transformylase → ↑adenosine.
    • Dose: Weekly.
    • Supplement: Folic acid (reduces ADRs).
    • ADRs: Oral ulcers, hepatotoxicity, myelosuppression, pneumonitis.
    • Contra: Pregnancy, liver disease.
  • Leflunomide:
    • MoA: Inhibits dihydroorotate dehydrogenase → ↓pyrimidine synthesis.
    • ADRs: Hepatotoxicity, teratogenicity, diarrhea.
    • Elimination: Cholestyramine wash-out.
  • Sulfasalazine (SSZ):
    • MoA: Prodrug → 5-ASA (anti-inflammatory) + sulfapyridine (antibacterial/immunomodulatory).
    • ADRs: GI upset, rash, oligospermia (reversible), yellow-orange skin/urine.
  • Hydroxychloroquine (HCQ):
    • MoA: ↑lysosomal pH, ↓TLR signaling.
    • ADRs: Retinal toxicity ('bull's eye maculopathy'), GI upset, skin pigmentation.
    • Monitor: Regular ophthalmologic exam.

⭐ MTX is the anchor drug for rheumatoid arthritis and is often the first csDMARD prescribed.

Table: Comparative Overview of csDMARDs

FeatureMethotrexateLeflunomideSulfasalazineHydroxychloroquine
MoADHFR inhibitor, ↑adenosineDihydroorotate dehydrogenase inhibitorProdrug (5-ASA + sulfapyridine)↑lysosomal pH, ↓TLR signaling
Key ADRsMyelosuppression, hepatotoxicity, oral ulcersHepatotoxicity, teratogenicity, diarrheaGI upset, rash, oligospermiaRetinal toxicity, GI upset
MonitoringCBC, LFTs, renal functionLFTs, BPCBC, LFTsOphthalmologic exam
PregnancyCategory XCategory XCategory B (folate needed)Generally considered safe (Cat C debated)

bDMARDs - BioLogic Blockers

  • Anti-TNF-α Agents: Infliximab (chimeric mAb), Etanercept (fusion protein), Adalimumab (human mAb), Golimumab (human mAb), Certolizumab pegol (pegylated Fab' fragment).
    • MoA: Neutralize TNF-α.
    • ADRs: Injection site/infusion reactions, ↑risk of infections (esp. TB reactivation, fungal), demyelination, worsening HF, drug-induced lupus.
    • Screening: TB, HBV, HCV.

    ⭐ Pre-treatment screening for TB (latent & active), HBV, and HCV is crucial before starting anti-TNF-α therapy due to risk of reactivation.

  • Rituximab (Anti-CD20 mAb):
    • MoA: Depletes B-cells.
    • Uses: RA refractory to anti-TNF agents.
    • ADRs: Infusion reactions, PML, HBV reactivation.
  • Abatacept (CTLA4-Ig):
    • MoA: T-cell co-stimulation modulator.
    • ADRs: ↑infections; ⚠️ avoid with TNF-α inhibitors.
  • Tocilizumab/Sarilumab (Anti-IL-6R mAb):
    • MoA: Block IL-6 receptor.
    • ADRs: ↑infections, dyslipidemia, ↑LFTs, neutropenia, GI perforation.
  • Anakinra (IL-1 receptor antagonist):
    • Less commonly used in RA.

Biologic DMARDs mechanisms of action

tsDMARDs & Combos - Tiny Targets, Team Tactics

JAK-STAT signaling pathways

  • JAK Inhibitors (tsDMARDs)
    • Oral: Tofacitinib, Baricitinib, Upadacitinib.
    • MoA: Inhibit Janus kinases (JAKs) → ↓cytokine signaling.
    • ADRs: ⚠️ ↑Serious infections (Herpes Zoster, TB), hyperlipidemia, cytopenias, ↑thrombosis, malignancy. FDA Boxed Warnings.
    • Monitoring: Lipids, CBC, LFTs (baseline & periodic).
  • Combination DMARDs
    • Strategy: MTX + bDMARD or MTX + other csDMARDs.
    • ⚠️ Avoid combining two bDMARDs (↑immunosuppression).
  • General DMARD Monitoring
    • Baseline: CBC, LFTs, renal fx, ESR/CRP, viral (HBV/HCV/TB) screen.
    • Periodic: For efficacy & toxicity.
  • DMARDs in Special Populations
    • Pregnancy:
      • Safer: HCQ, SSZ.
      • Contraindicated: MTX, Leflunomide.
    • Breastfeeding:
      • Generally compatible: HCQ, SSZ.
      • Avoid: MTX, Leflunomide.

⭐ Tofacitinib (a JAK inhibitor) carries FDA Boxed Warnings for serious infections, MACE, malignancy, and thrombosis.

High‑Yield Points - ⚡ Biggest Takeaways

  • Methotrexate (MTX): first-line DMARD for RA; folic acid supplementation is crucial.
  • Leflunomide: inhibits dihydroorotate dehydrogenase; an alternative to MTX.
  • Hydroxychloroquine (HCQ): monitor for retinal toxicity (bull's eye maculopathy).
  • Sulfasalazine: used in RA and IBD; side effects include hemolysis in G6PD deficiency.
  • TNF-α inhibitors (e.g., Infliximab, Adalimumab): screen for latent TB before starting.
  • Tofacitinib: an oral JAK inhibitor, for RA refractory to other DMARDs_._

Practice Questions: Disease-Modifying Antirheumatic Drugs

Test your understanding with these related questions

A patient of RA is taking methotrexate, steroids and NSAIDs since 4 months but activity of disease progression is same. What should be the next probable step?

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Flashcards: Disease-Modifying Antirheumatic Drugs

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_____ may be contraindicated during the 3rd trimester of pregnancy due to risk of premature closure of the ductus arteriosus

TAP TO REVEAL ANSWER

_____ may be contraindicated during the 3rd trimester of pregnancy due to risk of premature closure of the ductus arteriosus

NSAIDs

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