Design Study has a double-blind placebo-controlled crossover design: following signing informed consent and initial assessment 20 subjects who meet eligibility criteria will be randomized into one of two groups: group A will receive combination of methadone and naloxone in a ratio of 50:1 shown to be safe and effective in other trials during week 1 of the study and methadone only during week 2 of the study. Group B will receive methadone only during week 1 of the study and combination of methadone and naloxone in a ratio of 50:1 during week 2 of the study. Thus, all participants will receive combination of methadone and naloxone for one week and methadone alone for one week. Neither study participants, nor the pharmacists observing the doses, nor study personnel will know if naloxone is added to subjects' methadone preparations. Allocation to Group A or Group B will be done by random assignment. The pharmacy research medication management service will prepare the randomization code such that there will be a balanced assignment after every 4 subjects. Bowel functioning will be assessed quantitatively primarily using the Bowel Function Index (BFI) at initial assessment and at the end of weeks one (day 8) and two of the study (day 15). Also data on the number of complete spontaneous bowel movements (CSBMs), their temporal relationship to medication administration and outcome will be collected every day prior to administration of the next dose of methadone. In addition to parameters of bowel functioning Subjective Opiate Withdrawal Scale (SOWS) will be administered daily in order to assess potential opioid withdrawal symptoms.