Patterns of physician prescribing for opioid maintenance treatment in Ontario, Canada in 2014

Background: Despite concerns surrounding high patient volumes in methadone clinics, little is known about the practice patterns of opioid maintenance therapy (OMT) providers in Ontario. We examined the distribution of these services and how physician characteristics differ based on prescribing volume. Methods: We conducted a cross-sectional study among prescribers of methadone or buprenorphine to Ontario public drug beneficiaries in 2014 by stratifying physicians into low- (lower 50%), moderate- (51-89%) and high volume (top 10%) prescribers. We summarized the distribution of OMT prescription days dispensed and urine drug screens (UDS) ordered using Lorenz curves and examined physician characteristics using descriptive statistics. Results: We identified 893 OMT prescribers in 2014. Physicians were mostly male (67.5%; N = 603), and middle-aged (median was 50). High-volume methadone providers (N = 57) prescribed approximately 56% (N = 4,115,322) of the total days of methadone (Gini coefficient = 0.76, 95% CI 0.74-0.79) while high-volume buprenorphine providers (N = 64) prescribed 61% (N = 589,463) of the total days of buprenorphine (Gini coefficient = 0.78, 95% CI 0.75-0.80). On average, each high-volume methadone prescriber treated 435 OMT patients and billed 43 UDS per patient, while each high-volume buprenorphine prescriber treated 64 OMT patients and billed 22 UDS per patient. Daily OMT patient volume was on average 74 for high-volume methadone prescribers and 6 for high-volume buprenorphine prescribers. Conclusions: OMT services are highly concentrated among a small portion of OMT providers who carry high daily patient volumes. Future research should examine the quality of primary care received by their patients to better elucidate the possible consequences of this highly unequal distribution of services.