Extracellular adenosine is increased by which of the following DMARDs?: (A) Leflunomide, (B) Sulphasalazine, (C) Methotrexate, (D) Hydroxychloroquine
Answer is C. Methotrexate: Methotrexate inhibits an enzyme 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) transformylase leading to accumulation of AICAR, which blocks adenosine deaminase. Thus adenosine accumulates and it decreases inflammation by acting on adenosine receptors.