Lengthening the time intervals between doses of biological agents in psoriatic arthritis patients: A single-center retrospective study.

Anti-tumor necrosis factor (TNF) alpha therapy has changed the course of psoriatic arthritis (PsA), but clinical experience about lengthening of time intervals between drug administrations is still limited. The aims of the study were to evaluate: (1) the long-term efficacy (over a 4-year period) of etanercept/adalimumab in a subset of PsA patients who did not require switches; and (2) the progressive lengthening of time intervals between treatments in patients who achieved minimal disease activity (MDA). PsA outpatients attending the Rheumatology Clinic-University of Padova who took a single anti-TNF agent (etanercept/adalimumab) for a 4-year period were studied. Therapy efficacy was assessed using clinical, biochemical, and disease activity (DA) indexes. The intervals between treatments were empirically and progressively lengthened after MDA was reached and maintained. One hundred and forty-one patients (mean age, 51.22 ± 12.34 years; mean disease duration, 12.1 ± 8.42 years) treated with etanercept/adalimumab (47.5% and 52.5%, respectively) were studied. DA indexes showed a marked, persistent improvement in all the patients throughout 4 years. The interval between injections could be extended in 46.1% of the patients (35% for adalimumab, 58% for etanercept) without provoking relapses. The mean therapy interval at the end of the study period was 3.12 weeks for adalimumab 40 mg (with respect to 2 weeks) and 2.75 weeks for etanercept 25 mg (with respect to 0.5 weeks). The new therapy timetable also led to cost savings. In conclusion, lengthening the time intervals between injections of anti-TNF agents in PsA patients who reach MDA is safe, effective, cost-effective, and facilitates patient compliance.