OBJECTIVES: To describe policies of drug cost sharing in health insurance schemes and how the authors have assessed the effects where available. METHODS: A systematic review was conducted in 2009 and updated in 2013. RESULTS: Totally 28 studies were included. 1) Some insurance schemes introduced a new drug cost sharing program, the increase rates of total number of prescriptions were smaller compared with the non cost-sharing group; At the same time, prescription drug cost sharing also decreased use of essential drugs or adherence to medications which induced adverse effects on vulnerable population such as the poor, the elderly and patients with chronic diseases. Average prescription cost increase rate was lower in the cost sharing group than the non cost-sharing group. 2) For Different Tiers of Prescription Copayment System, there were some positive effects showing that the consumption of generic drugs increased in both single-tired and three-tiered groups, especially higher proportion in the three-tiered system. Higher levels of prescription drug cost sharing actually decrease inappropriate drug use with a relatively inelastic price elasticity of demand. For the patients with chronic diseases such as heart failure or diabetes, lower adherence of medication followed by higher copayment would increase risk of hospitalization. Different levels of copayment could control moral hazard of the patients with decreased rates of switching to a relatively more expensive drug and an increased rate of switching to drugs of equal or lesser cost. 3) Increasing cost sharing level was followed by decreasing the utilization of prescription drugs and increasing in out of pocket especially for the vulnerable population.  CONCLUSIONS: To increase or decrease the level of cost sharing could change the beneficiaries’ behavior, the vulnerable population were more sensitive than the general. Different levels of cost sharing method seem as one of the successful tools to control moral hazard.