Methadone treatment for HIV prevention-feasibility, retention, and predictors of attrition in Dar es Salaam, Tanzania: a retrospective cohort study

Background: People who inject drugs (PWID) in Dar es Salaam, Tanzania, have an estimated human immunodeficiency virus (HIV) prevalence of 42%-50% compared with 6.9% among the general population. Extensive evidence supports methadone maintenance to lower morbidity, mortality, and transmission of HIV and other infectious diseases among PWID. In 2011, the Tanzanian government launched the first publicly funded methadone clinic on the mainland of sub-Saharan Africa at Muhimbili National Hospital.

Methods: We conducted a retrospective cohort study of methadone-naive patients enrolling into methadone maintenance treatment. Kaplan-Meier survival curves were constructed to assess retention probability. Proportional hazards regression models were used to evaluate the association of characteristics with attrition from the methadone program.

Results: Overall, 629 PWID enrolled into methadone treatment during the study. At 12 months, the proportion of clients retained in care was 57% (95% confidence interval [CI], 53%-62%). Compared with those receiving a low dose (<40 mg), clients receiving a medium (40-85 mg) (adjusted hazard ratio [aHR], 0.50 [95% CI, .37-.68]) and high (>85 mg) (aHR, 0.41 [95% CI, .29-.59]) dose of methadone had a lower likelihood of attrition, adjusting for other characteristics. Older clients (aHR, 0.53 per 10 years [95% CI, .42-.69]) and female clients (aHR, 0.50 [95% CI, .28-.90]) had a significantly lower likelihood of attrition, whereas clients who reported a history of sexual abuse (aHR, 2.84 [95% CI, 1.24-6.51]) had a significantly higher likelihood of attrition.

Conclusions: Patient retention in methadone maintenance is comparable to estimates from programs in North America, Europe, and Asia. Future implementation strategies should focus on higher doses and flexible dosing strategies to optimize program retention and strengthened efforts for clients at higher risk of attrition.