Rate of retention and related factors on patients under methadone maintenance treatment in Beijing: a prospective cohort study

Abstract

To study the rates of retention and associated factors on patients under methadone maintenance treatment (MMT) in Beijing. A prospective cohort was conducted among 548 patients who enrolled in MMT clinics during 2004 - 2006 in Beijing. Log-rank method and Cox PH regression models were used to study related factors associated with long-term retention. Of the 548 patients, 463 (79.6%) were males, with 515 (94.0%) under Han ethnicity. 443 (80.8%) of them were unemployed with 449 (81.9%) as injecting drug users at the time of enrollment. The average age and duration of drug abuse at enrollment were 37.3 ± 6.7 and 9.1 ± 4.0 years, respectively. The median length of treatment was 2.1 years with five-year retention rate as 41.2%. The long-term retention rates between different dosages (Log-rank χ(2) = 10.527, P = 0.005), treatment ratio (Log-rank χ(2) = 19.027, P < 0.001) and illicit drug use (Log-rank χ(2) = 159.485, P < 0.001) showed significant differences, statistically. Factors as having high education level (HR = 0.76, P = 0.021), with daily dosage 60 mg/day or more (HR = 0.64, P = 0.002), having 1% - 9% times urine morphine positive result (HR = 0.32, P < 0.001) seemed to be able to predict the lower risk of dropout during the follow-up period. However, frequent illicit drug use (> 20%) (HR = 2.92, P < 0.001) could increase the risk of dropout. Treatment with higher dosage (≥ 60 mg/day) of methadone seemed to have decreased the possibility of dropout during the follow-up period, whereas frequent illicit drug use (≥ 20%) was important risk factor causing long-term retention.