Low-Dose (17.5 mg/Day) Acitretin: Comparable Efficacy Without the Side Effects?

Inclusion Criteria: * Male or female subjects 18 years of age or older. * Surgically sterile females. Females who have had a hysterectomy or oophorectomy or completed menopause (post-menopausal for at least 1 year) are allowed. Men must agree to use 2 forms of birth control (eg condoms, spermicide). * Stabilized on a phototherapy regimen for 4 weeks. * Compliant with acitretin dosing at 25 mg/day and experiencing retinoid-related adverse events which, in the clinical judgement of the investigator, may benefit from a reduction in dose to 17.5 mg/day. * Able to complete the study and to comply with the study instructions. * Adherence to alcohol avoidance during acitretin therapy and for 2 months after discontinuation of acitretin. * Subjects must be willing to not donate blood during the study as well as 3 years following completion of this study. * Capable of understanding and willing to provide signed and dated written voluntary informed consent (and any local or national authorization requirements) before any protocol specific procedures are performed. Exclusion Criteria: * Uncontrolled hypertriglyceridemia. * Guttate, erythrodermic, or pustular psoriasis. * Severely impaired hepatic function, \> 3 times the upper limit of normal and the clinical investigator's judgment. * Use of systemic immunosuppressant agents (eg. Methotrexate, cyclosporine, thioguanine, azathioprine, alefacept, egalizumab, corticosteroids) within 4 weeks of baseline and throughout the study. * Topical vitamin A, vitamin D or analogue preparations, or anthralin within 2 weeks of study initiation. * History of known or suspected intolerance to any of the ingredients of the investigational study product. * Used over the counter (non-prescription) medications or herbal remedies within 2 weeks of dosing, unless agreed upon as not clinically relevant by the principal investigator. * Participated in a previous study of the same study product. * Currently using any medication which, in the opinion of the investigator, may affect the evaluation of the study product or place the subject at undue risk. * Currently suffering from any disease or condition which, in the opinion of the investigator, may affect the evaluation of the study product or place the subject at undue risk. * Any major illness within 30 days before screening examination. * Considered immunocompromised. * A clinically relevant history of or current evidence of abuse of alcohol or other drugs. * Use of any investigational drugs or treatments during the study or within 4 weeks of the baseline visit. * Women of child-bearing potential (see inclusion criteria).