SUMMARYCell-specific pharmaceutical technologies promise mechanistic insight into clinical drugs―those that treat, and often define, human disease. In particular,DART(drug acutely restricted by tethering) achieves genetically programmable control of drug concentration over cellular dimensions. The method is compatible with clinical pharmaceuticals and amenable to studies in behaving animals. Here, we describeDART.2, comprising three advances. First, we improve the efficiency of chemical capture, enabling cell-specific accumulation of drug to ∼3,000-times the ambient concentration in 15 min. Second, we develop tracer reagents, providing a behavior-independent measure of cellular target engagement in each animal. Third, we extend the method to positive allosteric modulators and outline design principles for this clinically significant class. We showcase the platform with four pharmaceuticals―two that weaken excitatory (AMPAR) or inhibitory (GABAAR) chemical neurotransmission, and two that strengthen these forms of synaptic communication. Across four labs, we tested reagents in the mouse cerebellum, basal ganglia, visual cortex, and retina. Collectively, we demonstrate robust, bidirectional editing of chemical neurotransmission. We provide for distribution of validated reagents, community design principles, and synthetic building blocks for application to diverse pharmaceuticals.