Interleukin (IL)-17 and IL-23 inhibitors have transformed psoriasis care, delivering high clearance rates and quality-of-life gains. Nevertheless, inadequate response or adverse events can lead to treatment discontinuation or biologic switching. Dose modifications are also commonly implemented in routine practice to optimize efficacy, safety, and cost. The objective of this study is to characterize real-world outcomes of dose adjustment and switching of IL-17 and IL-23 inhibitors in Thai patients with psoriasis. We retrospectively reviewed 173 treatment courses with IL-17 inhibitors (secukinumab, ixekizumab, and brodalumab) and the IL-23 inhibitor guselkumab, documenting loading regimens, maintenance dosing, efficacy to Week 52, and switching events. At Week 12, full loading and standard maintenance dosing were associated with higher response rates in most cases. Ixekizumab was least often given with a full loading dose or standard maintenance dosing. By Weeks 24 and 52, reduced-dose regimens achieved comparable or better outcomes, suggesting careful patient selection. Thirty courses underwent biologic switching, predominantly for secondary failure. Intraclass switching among IL-17 inhibitors predominated. Switching from IL-23 to IL-17 inhibitors potentially outperformed both intraclass IL-17 switching or IL-17-to-IL-23 transitions. Erythrodermic psoriasis and higher baseline disease severity predicted switching, whereas incomplete loading doses and dose reductions did not. In conclusion, full loading and standard maintenance regimens facilitate early treatment response, while dose reduction in carefully selected patients can sustain long-term disease control without increasing the risk of switching.
