Which drug is a conventional disease-modifying antirheumatic drug (csDMARD)?

• A. MTX
• B. Infliximab
• C. Tofacitinib
• D. Adalimumab

Answer: (A)

Conventional DMARDs are the traditional drugs used to slow joint damage in rheumatoid arthritis, usually started early and taken regularly to dampen the overall immune response. Methotrexate is the quintessential csDMARD because it’s the classic, widely used agent with a well-established role as first-line therapy. At low doses, it acts as a folate antagonist that reduces immune cell proliferation and inflammatory signaling, with additional anti-inflammatory effects such as increased extracellular adenosine. This profile fits the traditional category of csDMARDs used to modify disease course.

Infliximab and adalimumab are biologic DMARDs; they are monoclonal antibodies that target and neutralize tumor necrosis factor-alpha, usually administered by injection and often used in combination with methotrexate. Tofacitinib is a targeted synthetic DMARD (tsDMARD), a small-molecule JAK inhibitor taken orally that disrupts signaling in several cytokine pathways. These differ from conventional csDMARDs in mechanism, administration, and classification, which is why methotrexate stands out as the conventional csDMARD.