Dose Tapering Study of Adalimumab in Psoriasis

Patients will be included after signing informed consent and randomized in either a standard dose arm or a concentration based arm based on prior Ctrough measurements. In the concentration based arm, dosing frequency will be lowered to once every 3 weeks. If patients still have supratherapeutic Ctroughs of adalimumab, these patients will continue adalimumab self-administration every 4 weeks. In the standard based arm, patients will continue on standard dosing schedule. During each study visit blood will be taken in order to quantify Ctroughs. In addition, Psoriasis Area and Severity Index (PASI) and Investigator's Global Assessment (IGA) score will be evaluated by a physician. Patients complete the Dermatology Life Quality Index (DLQI) and European quality of life EQ-5D instrument at each visit. In addition, in a subset of patients in each treatment arm, additional sampling will be collected by dried blood spot sampling in order to build a PK(PD) model for adalimumab.