Non-adherence with antipsychotics is common in patients with a psychotic disorder and is associated with more relapses and higher healtcare costs. Penfluridol is a first generation antipsychotic drug and currently the only long-acting oral agent that can be taken once a week. Second generation oral antipsychotic drugs such as olanzapine and risperidone have to be taken daily. In addition, penfluridol is also cheaper than oral second-generation antipsychotics mostly used today (including olanzapine and risperidone). Since this agent can be administered on a weekly basis, we expect that penfluridol will enhance patient adherence and therefore lower healthcare costs . This multi-center open label randomized controlled trial will provide an initial insight into the (cost-) effectiveness of this agent as compared to second generation antipsychotics, and whether the clinical guidelines could be updated.