This dissertation examines the unintended public health consequences of several supply- and demand-side drug control policies in the United States. The first paper examines whether the introduction of an abuse-deterrent formulation of OxyContin increased the homicide rates. This paper makes three main contributions related to the literature on the unintended consequences of OxyContin reformulation, and more broadly, of policies addressing prescription opioid use. First, it provides new evidence that the rise in homicides linked to pre-reformulation abuse was transitory, contrasting with prior findings. Second, it documents how reformulation affected homicide victims across age groups, revealing that the pattern mirrored homicides among individuals in their late teens and early twenties, consistent with gang-related violence. Third, it finds that medical marijuana legalization helped mitigate suicide risk in this context. Together, these findings further confirm the connection between OxyContin reformulation and homicide and demonstrate the potential effectiveness of indirect interventions. The second paper examines how suicide rates among the general population evolved following OxyContin reformulation in the context of tightening opioid prescribing practices. It finds that variation in pre-reformulation dispensing patterns between different types of retail pharmacies, introduced as a novel measure of local availability of pain medications, was negatively associated with suicide rates in the general population, while pre-reformulation exposure to OxyContin abuse was positively associated. These effects appear largely independent, suggesting that tapering may help reduce suicide among former abusers of OxyContin, but that preserving adequate access to pain treatment remains critical. The third paper investigates the impact of the Safe Neighborhoods and Schools Act, commonly known as Proposition 47, on California's prevalence of HIV, Chlamydia, and Gonorrhea. While regularized synthetic control estimates show little evidence that the reform increased sexually transmitted infections in the general population, they document a significant rise in HIV prevalence attributable to injection drug use among older males, a group disproportionately affected by housing instability and substance use. These findings underscore the importance of considering public health spillovers when assessing efforts to reduce incarceration.