Background & Objective: Drug abuse causes severe gastrointestinal, neurological problems and dependency. For maintenance therapy of opiate addiction, long-acting opioids like methadone are used. Since incorrect use of methadone, leads to serious complications, this study aimed to evaluate the prevalence of methadone.

Materials & Methods: This cross-sectional study was done with a sample size of 151 patients in addiction treatment centers Fasa Shariati Hospital, during 6 months. After reviewing the cases of patients who were taking methadone for addiction and completed their demographic information, check list of questions about the different effects of methadone was completed for each patient. The data was statistically analyzed by Mann-Whitney test.

Results: The average age of participants in the scheme was 31/71. The results showed that the most common side effects of methadone, is gastrointestinal complications (77/5 percent). In addition, between the effects and duration of methadone there is a significant relationship. However, other effects were not associated with duration of use.

Conclusion: According to the results, the need for continuous follow-up of patients undergoing methadone treatment for drug complications and such findings can even be transferred to the relevant authorities, in order to add assessment side effects of treatment is necessary in the case of defined. The patients’ need to medication may cause endurance of bothersome symptoms. While it can affect their quality of life.