The use of serum methotrexate level as an assessment of biochemical drug adherence in psoriasis

Psoriasis is a common inflammatory skin condition affecting approximately 2–3% of people worldwide. Methotrexate (MTX) is a cheap and effective drug that is often recommended as the first-choice systemic agent for psoriasis. Around 40–50% of patients achieve a good response; however, mechanisms of nonresponse are poorly understood. It is not known whether biochemical MTX adherence in patients with psoriasis is suboptimal and requires intervention. Our aim was to audit biochemical MTX adherence using a sensitive liquid chromatography–tandem mass spectrometry in patients prescribed oral MTX for the treatment of psoriasis at our tertiary dermatology centre. Ethical approval for this audit was not required as confirmed by the Health Research Authority.