Differences in treatment outcomes by frequency and drug preference for dual users of heroin and crack in opiate substitution therapy – a pilot study
Felicia Heidebrecht, Mary Bell Macleod and Lynne Dawkins
Research evidence shows that dual users of heroin and crack/cocaine have poorer treatment outcomes. In the UK, national statistics on drug use document an increase in the prevalence of dual use of heroin and crack/cocaine among drug users in opiate substitution therapy (OST). Clinical treatment guidelines recommend that the crack use needs to be addressed in addition to the pharmacological treatment for heroin dependency. However, dual users are frequently regarded as a homogeneous group.
The aim of this study was to compare retention, and heroin and crack use in OST among heroin users with different patterns of dual use.
Participants: Drug users starting OST between November 2014 and March 2015 in one community drug service in London, UK (N=42, mean age 39.3 ± 8.8 years, 78.6% male).
Data collection: Clinical records, questionnaires assessing drug use and preference before OST start and drug use at three months follow-up, urine drug screens.
Patterns of drug use before OST start: Participants were divided into four groups: heroin-only (no crack use), occasional crack use, daily dual use with preference for crack, daily dual use with no particular preference (All participants used heroin daily).
Statistical analyses: Descriptive statistics, Kendall’s tau.
The retention in treatment at three months was highest for heroin-only users (100%), followed by daily dual users with preference for crack (80%), and lowest for the occasional users of crack (50%). The retention at six months was lower for all groups, however it followed the same trend.
From the participants still in treatment at three months, the highest rate of heroin abstinence was achieved by the daily dual users with preference for crack (90%), and the lowest by the occasional crack users (7%). The highest rate of crack abstinence was achieved by occasional users (35.7%) and the lowest for daily dual users with preference for crack (20%). Daily dual users with no particular preference were either abstinent for both drugs at 3 months (23.5%) or continued using both of them. Because of the low numbers due to high drop-out rate and unequal group sizes it was not possible to conduct statistical analyses.
The correlation between the number of days using crack and heroin at three months was found significant only for the daily dual users with no particular preference (τ(11)=.949, p<0.001).
When on OST medication, daily dual users with preference for crack were able to stop using heroin while continuing using crack, while dual users with no particular preference could not separate the two drugs. These results suggest that daily dual users might not be a homogeneous group.
Studies with higher numbers are needed to assess significance, to further segment the group of occasional users, and to define clear outcome patterns which could inform the development of tailored interventions for subgroups of dual users.