INTRODUCTION
Methotrexate (MTX) is a commonly used agent in the treatment of moderate to severe chronic plaque psoriasis
(CPP). Its effectiveness has been established in the dermatological literature.1-4 Even though the use of parenteral MTX was first described in the 1960’s,5-9 it was not a routine treatment modality for the next 40 years. Initially, parenteral MTX was given as an intra-muscular injection, which was difficult to self-administer and therefore needed medical input on a weekly basis. Pharmacies were also reluctant to dispense this formulation as it was difficult to produce and carried the risk of toxicity with even a slight deviation in dose. Subcutaneous (SC) and intramuscular injections deliver bioequivalent doses of MTX, with the former more convenient and less painful compared to the latter.10 The development of a patient-administered SC MTX was therefore an innovation that has helped popularise this therapy.
There is good evidence of the efficacy of SC MTX in the rheumatological
literature,11,12 SC MTX has a better bioavailability compared to oral MTX and is also known to cause fewer gastro-intestinal side-effects.13 It is also documented to be more effective than oral MTX at the same dose in rheumatoid arthritis. 14,15 Even though a recent review has recommended the use of SC MTX in CPP, there is no published clinical series evaluating its role in psoriasis.16 This study aimed to collect data from three UK dermatology centres to assess the effectiveness of SC MTX in CPP, focusing on those who had