Patterns of adherence to oral methadone: implications for prescribers

We investigated patterns of nonadherence to substitute treatment among patients attending an inner London community drug dependency unit and explored factors associated with nonadherence. We undertook 91 face-to-face confidential interviews with methadone-maintained patients attending community pharmacies. Thirty-eight patients (42%) had been either partial or poor adherers to their prescribed methadone regime in the past month. Multinomial logistic regression revealed that compared to full adherers, both poor adherers and partial adherers were more likely to be prescribed by unsupervised consumption. Poor adherers were also more likely to have less frequent pickups. There were seven types of nonadherent behavior detected, with dose splitting being the most prevalent (34%), followed by dose storage (28%) and missed pickups from the pharmacy (18%). We suggest that prescribers include an assessment of medication adherence at regular patient reviews as supervised consumption does not solve all adherence problems with methadone. New approaches to encouraging adherence, including a more systematic monitoring of adherence to improve the effectiveness of methadone programs, are needed.