Individuals with intellectual and developmental disability (IDD) can have a high prevalence of pain, which can be managed with prescription opioids. However, the prevalence of substance use disorder is also high in this population, raising concern about opioid-related adverse events.

To assess the risk of opioid-related adverse events following opioid initiation among adults with versus without IDD.

We conducted a population-based, propensity score matched cohort study on all adults starting prescription opioid therapy in Ontario, Canada, between January 2013 and December 2018. The outcomes of interest were opioid toxicity, new opioid use disorder (OUD) diagnosis and dose escalation (≥90 mg morphine or equivalent) in the year after opioid initiation. We used Cox proportional hazards models to assess the association between IDD diagnosis and each outcome.

The hazards of opioid toxicity and OUD were significantly higher in those with IDD compared with those without IDD in unmatched analyses (opioid toxicity hazard ratio 3.19, 95% CI 2.81–5.18; OUD hazard ratio 2.36, 95% CI 2.10–2.65), whereas the hazard of dose escalation was significantly lower (hazard ratio 0.76, 95% CI 0.66–0.88). Findings were no longer significant in propensity score matched models for opioid toxicity and dose escalation, whereas the hazard of OUD diagnosis was attenuated substantially in those with IDD (hazard ratio 0.79, 95% CI 0.68–0.91).

IDD diagnosis is not a driver of opioid-related harm. The increased risk we observed is likely driven by various risk factors often present in this population.

Differences in patient adherence to various disease-modifying drugs (DMDs) in the treatment of multiple sclerosis (MS) are not well understood. The goal of this study was to evaluate adherence of adult MS patients in Ontario with public drug plan coverage to various DMDs: intramuscular interferon beta-1a (i.m. IFNβ-1a, Avonex), subcutaneous interferon beta-1a (s.c. IFNβ-1a, Rebif), subcutaneous interferon beta-1b (IFNβ-1b, Betaseron) or glatiramer acetate (Copaxone).

In this retrospective cohort study, Ontario Public Drug Plan beneficiaries aged 15 or older who were newly treated with i.m. IFNβ-1a, s.c. IFNβ-1a, IFNβ-1b or glatiramer acetate between April 2006 and March 2008 were followed forward until treatment discontinuation, switch to another DMD or a maximum two year follow-up period. Cumulative persistence rates were analyzed by the Kaplan-Meier method. The proportion of patients reaching the study endpoints after the two year follow-up period was also calculated.

Cumulative persistence rates for all four DMDs were similar over time (p=0.80), ranging from 73.6-79.1% at six months, 59.1-63.1% at one year and 41.5-47.4% at two years. After two years, the proportion of patients who had discontinued treatment, switched to another DMD or died was similar among DMDs (p=0.79, Fisher's exact test). Switching between DMD types was low and occurred in 3.4-6.5% of new DMD users.

Adherence to DMDs in adult MS patients in Ontario is poor, which is consistent with previously reported adherence rates to MS DMDs in other regions. No significant differences in adherence exist between the DMDs evaluated in this study.

Differences in Multiple sclerosis (MS) disease-modifying therapy (DMT) prescribing patterns between different groups of neurologists have not been explored.

To examine concentrations of prescribing patterns and to assess if MS-specialists use a broader range of DMTs relative to general neurologists.

We conducted a cross-sectional study using administrative claims databases in Ontario, Canada to link neurologists to 2009 DMT prescription data. MS specialization was defined using both practice location and prescription patterns. Lorenz curves and Gini coefficients were constructed to examine prescribing patterns, separating neurologist characteristics dichotomously and separating Avonex from the other standard DMTs (Betaseron, Rebif and Copaxone). Gini coefficient 95% confidence intervals (CIs) were derived using jack-knife statistical techniques.

Prescriptions were highly concentrated with 12% of Ontario neurologists prescribing 80% of DMTs. There was a trend towards Avonex being more commonly prescribed relative to the other DMTs. When MS specialization was defined by DMT prescribing, high-volume prescribing neurologists showed a broader range of DMT prescribing (Gini 0.38-0.44) in comparison to low-volume prescribers (Gini 0.57-0.66).

The majority of DMTs are prescribed by a small subset of neurologists. High-volume prescribing MS-specialists show more variability in DMT use while low-volume prescribers tend to individually focus on a narrower range of DMTs.