OBJECTIVES: Opioid induced constipation (OIC) is the most common, persistent and debilitating side effect reported in patients receiving opioids to manage pain. Laxatives are commonly prescribed to treat OIC but in some patients they provide inadequate response. Movantik is a peripherally acting mu-opioid receptor antagonist used to treat patients with inadequate response to laxative(s) (LIR). A cost effectiveness model was constructed from the UK payer perspective to compare Movantik 25mg with placebo, rescue laxatives, Relistor and Targin in LIR patients. METHODS: Two Phase III 12-week placebo-controlled RCTs, KODIAC 4 and 5, provided data on response rates, transition probabilities and EQ-5D inputs for the model for Movantik, placebo and rescue laxatives. Tolerability data in the model is generated from both these studies and KODIAC 8, a 52-week safety study. The model comprises a decision tree for the first 4 weeks of treatment, followed by a Markov model with a 4-week cycle length and the following states: non-OIC on treatment, OIC, non-OIC not on treatment and death. A mixed treatment comparison provides data on OIC status for Relistor and Targin. Resource utilization data used in the model were gathered from a UK-based burden of illness study and physician surveys. RESULTS: Movantik has an ICER of £10,849 vs. placebo, of £12,639 vs. placebo & rescue laxatives and is dominant vs Relistor over a 5 year time horizon in LIR patients. The probabilistic sensitivity analyses indicates that for these comparisons, based on a threshold of £20,000, Movantik has a respective probability of 91%, 83% and 100% of being cost effective. In a population of LIR patients who are taking step 3 opioids, Movantik is dominant vs. Targin over a 5 year time horizon. CONCLUSIONS: Movantik is a cost-effective treatment option for patients with OIC who have experienced inadequate response to laxative(s).