Dynamic cost–benefit analysis of drug substitution programs

This paper studies optimal spending for drug substitution programs in the context of a dynamic epidemic model of both drug use and drug use-related infections. Two type of costs are considered in addition to control costs: social costs resulting from individuals being dependent on drugs; additional costs due to drug users being vulnerable to infections like hepatitis C or HIV. Analysis of the model demonstrates that the long-run equilibrium is not necessarily unique. Instead, there may be multiple equilibria. Which of these equilibria is optimal depends on the initial conditions for the number of drug addicts and the number of those who are infected. So, for a given set of epidemic parameters, it may be optimal to spend a lot on substitution programs that reduce the number of drug addicts or to spend little and to accept a high level of drug use.