The six months effectiveness was investigated in the trial on injectable heroin by comparing the percentage responders among the patients in the co-prescribed heroin and methadone alone group halfway their intended treatment period, i.e. six months after baseline. The underlying study question pertained to the six months effectiveness of ongoing treatment with co-prescribed heroin, compared to that of ongoing methadone alone treatment. Analogous to the investigations into the month 12 effects described in the previous paragraph, the analysis was conducted in the intention-to-treat population, applying LOCF, and using a logistic regression model.

Effectiveness of co-prescribed heroin versus methadone alone treatment after six months
At the month 6 assessment-point, 43.4% of the participants in the heroin group were responders, compared to 27.6% in the methadone group (see Figure 11: left-hand bars). Compared to the response percentages which were reported earlier for month 12 (right-hand bars), the difference in response between the heroin and methadone group increased from 15.8% after six months to 25.0% after twelve months.

Figure 11. Effectiveness of co-prescribed injectable heroin versus methadone alone treatment after six and twelve months (n =174)

Adjusted for differences in response between the treatment sites, the Odds-Ratio corresponding with this difference of 15.8% was 2.03 (95%-CI: 1.07-3.85; p=0.0296). Treatment response at month 6 was not significantly related to either treatment site or treatment-by-site interactions. According to the Hosmer and Lemeshow goodness-of-fit test, the data fitted the regression model (X²=2.55; df=7; p=0.92).