Factors associated with drug shortages in Canada: a retrospective cohort study

BACKGROUND: To monitor the magnitude of the drug shortage problem in Canada, since 2017, Health Canada has required manufacturers to report drug shortages. This study aimed to identify the factors associated with drug shortages in Canada. METHODS: We conducted a retrospective cohort study of all prescription drugs available on the market between Mar. 14, 2017, and Sept. 12, 2018, in Canada. All drugs of the same active ingredient, dosage form, route of administration and strength were grouped into a "market." Our main outcome was shortages at the market level, determined using the Drug Shortages Canada database. We used logistic regression to identify associated factors such as market structure, route or dosage form, and Anatomic Therapeutic Chemical (ATC) classification. RESULTS: Among the 3470 markets included in our analysis, 13.3% were reported to be in shortage. Markets with a single generic manufacturer were more likely to be in shortage than other markets. Markets with oral nonsolid route or dosage form were more likely to be in shortage than those that were oral solid with regular release (odds ratio [OR] 1.66, 95% confidence interval [CI] 1.11 to 2.49). Markets for sensory organs were more likely to be in shortage than most other ATC classes. Markets with a higher proportion of drugs covered by public insurance programs were more likely to be in shortage (OR 1.03, 95% CI 1.00 to 1.05 per 10% increase). INTERPRETATION: Markets with a single generic manufacturer were most likely to be in shortage. To ensure the security of drug supply, governments should be vigilant in monitoring markets with a single generic manufacturer, with complex manufacturing processes, with higher demand from public programs or those that are in certain ATC classes.