Global supply chains for active pharmaceutical ingredients (APIs) are highly centralized in certain countries and are susceptible to supply-chain shocks. However, there is no systematic monitoring or global coordination to manage risk and ensure equitable supply continuity during public health emergencies. In this study, we applied quasi-experimental methods on shipment-level customs data to determine how prices and export volume for APIs exported from India were affected by the COVID-19 pandemic. We found that API prices for key essential medicines not used for COVID-19 did not change significantly in the year after the World Health Organization pandemic declaration, but volume decreased by 80 percent. Prices for medicines speculatively repurposed for COVID-19, such as hydroxychloroquine and ivermectin, increased by as much as 250 percent compared with prices for nonrepurposed medicines, but only ivermectin saw a decrease in volume. Systematic monitoring of API markets, investments to promote supply diversification, and legal and political reforms to disincentivize price speculation could support supply-chain resilience and safeguard access to medicines.