Compliance in terms of PPC (or placebo) will be monitored by 4 methods: patient diary, pill count of the medication and monthly urine analysis for the presence of a riboflavin marker. Patients will consume 60 mg riboflavin per day. Riboflavin is rapidly excreted in the urine and is fluorescent when passed under an ultraviolet lamp. In addition, spot checks of blood levels of dilinoleoylphosphatidylcholine (DLPC, the main phosphatidylcholine species of PPC) will validate compliance.