In this paragraph the treatment participation of patients will be described. Patients were defined as 'treatment completer' if they were still participating in the intended treatment condition in month 12 of the study as evidenced by the drug accountability data. Thus, patients in the control group A were considered to be treatment completer if they still received oral methadone in month 12. Similarly, patients in the experimental groups B and C were considered to be treatment completer if they still received medically co-prescribed heroin in month 12.

As is shown in Figure 19 all but one patients in the methadone group started their methadone treatment offer. This is because these patients were already taking part in a methadone maintenance treatment program at the time of randomization. In the 12th month after baseline, 17 additional patients were no longer receiving methadone maintenance treatment, i.e., 12.9% of the patients in the control condition had 'dropped out' the treatment regimen offered at the beginning of the trial. The remaining 87.1% of the control patients had completed treatment.
It can be seen from Figure 19 that six patients (5.1%) never started the co-prescribed heroin treatment for 12 months (group B). In the 12th month after baseline, 31 more patients (26.5%) were no longer treated with co-prescribed heroin. For almost half of the patients the termination of the heroin treatment was non-voluntary. They were expelled from the program (six patients), had become incarcerated (two patients), or were forced to stop the treatment for medical reasons (three patients) or because of problems with the alcohol policy of the treatment site (one patient). Fifteen patients ended the treatment with co-prescribed heroin voluntary for various personal reasons and for four persons the reasons why they did not complete treatment is unknown. The remaining 80 patients in group B were still treated with co-prescribed heroin at the end of the study and hence were considered as 'treatment completer' (68.4%).

Figure 19. Disposition of randomized patients

In a similar way it can be seen that 21 patients in group C (17.7%), who were treated with oral methadone for the first six months, did not start the treatment with co-prescribed heroin six months after baseline. For a minority this was due to non-voluntary reasons (four patients). Twelve patients did not start the heroin treatment for a variety of personal reasons and for five patients it is unknown why they did not start the treatment with heroin. In addition, another 16 patients were no longer treated with heroin in the 12th month after baseline (13.5%). Again, for almost half of the patients the termination of the heroin treatment was non-voluntary. They were expelled from the program (two patients) or had become incarcerated (four patients). Seven patients ended the treatment with co-prescribed heroin voluntary for various personal reasons and for three persons the reasons why they did not complete treatment is unknown. The remaining 82 patients in group C were still treated with co-prescribed heroin at the end of the study and hence were considered as 'treatment completer' (68.9%).
The differences in treatment completion between on the one hand the 12 months methadone condition (87.1%) and on the other hand the 12 months co-prescribed heroin condition (68.4%) and the six months co-prescribed heroin condition (68.9%) are statistically significant (Treatment completion group A versus group B: Odds-Ratio=0.32; 95%-CI: 0.17-0.60; p=0.0004, and treatment completion group A versus group C: Odds-Ratio=0.33; 95%-CI: 0.17-0.61; p=0.0005).

Treatment completing patients in the control condition had been prescribed methadone on 330 days (median) during the experimental treatment year. The mean dosage of methadone prescribed to treatment completers in the control group was 67 mg (sd=23.2 mg).
The mean methadone dosage in the experimental group B was 57 mg (sd=18.1 mg), which is significantly lower compared to the control group (t-value=3.23; df=193; p=0.001). In addition, treatment completing patients in the experimental group B visited the heroin dispensing units on 353 days (median) and 2.1 times per day (median). The mean heroin dosage prescribed was 263 mg per visit (sd=59.0 mg) and 547 mg per day (sd=173.5 mg).
Similarly, for treatment completing patients in group C the mean methadone dosage prescribed amounted to 66 mg (sd=27.4 mg) during the six months that co-prescribed heroin was offered. This methadone dosage does not differ from the dosage prescribed in the methadone control condition (67 mg) (t-value=0.26; df=201; p=0.80). In addition in this six months period, treatment completers in group C visited the heroin dispensing units on 169 days (median) and 2.1 times per day (median). The average heroin dosage prescribed was 252 mg per visit (sd=68.0 mg) and 539 mg per day (sd=151.2 mg).