Methotrexate dosage and laboratory monitoring in patients with psoriasis and psoriatic arthritis: A retrospective analysis of prescription patterns and financial impact in dermatology and rheumatology settings.

Background Methotrexate (MTX) is a disease-modifying drug used for psoriasis (PsO) and psoriatic arthritis (PsA), but dermatology and rheumatology guidelines differ in dosing and monitoring recommendations. Objectives To compare methotrexate dosing and monitoring practices in dermatology and rheumatology, assess adverse drug reactions, and analyse the financial impact of rigorous monitoring. Methods This observational, electronic medical record-based retrospective chart review included psoriasis and psoriatic arthritis patients started on methotrexate at the dermatology and rheumatology departments at a tertiary care centre in 2020-2021. Patients with concurrent hepatotoxic/myelotoxic medications, inadequate follow-up, or abnormal baseline laboratory tests were excluded. Data regarding demographics, relevant medical histories, clinical variables, methotrexate dosing, frequency of laboratory monitoring, adverse events, and resource utilization were recorded and analysed. Descriptive statistics (means/percentages) and inferential tests (Chi-Square Test or Mann- Whitney Test) were used based on data normality (p<0.05 considered significant). Results The study included 100 psoriasis and psoriatic arthritis patients each. The psoriatic arthritis patients were given higher methotrexate doses initially but underwent less frequent laboratory monitoring compared to psoriasis patients. The incidence of hepatotoxicity was comparable between the two groups. However, leukopenia was observed more frequently in psoriatic arthritis patients. Methotrexate monitoring under dermatologists cost 44% more than that under rheumatologists over 6 months (Rs 4766.08± 1631.9 vs Rs 3290.32± 1207.8). Limitations The single centre, small sample size, retrospective chart review, and convenience sampling in this study may all limit the generalisability of the findings. Conclusion Current methotrexate guidelines in dermatology recommend lower doses and more frequent monitoring than rheumatology guidelines. Insights from this study and comparison with rheumatology practices and existing literature highlight the potential for designing large-scale, multicentric, non-inferiority studies that could eventually help develop more efficient and streamlined methotrexate monitoring protocols for dermatology and rheumatology, ultimately improving patient adherence, safety and affordability.