Objectives: The mechanism of action of drugs that depress the central nervous system (CNS) was unknown until molecular pharmacology discovered each drug's exact role. The benefit of knowing the mechanism of action is to design a new drug that could have the same efficacy as the prototype drug but with fewer side effects. Some of the available CNS depressant drugs that were abused or illegally used could be modified to make them used medically. Methods: We reviewed various published articles in PubMed and Google Scholar that focused on CNS depressants' molecular pharmacology.Results: It was clear that at specific plasma concentrations of ethyl alcohol showed almost same mode of action of propofol by targeting the extrasynaptic GABA-A receptors, which causes tonic GABAergic inhibition. Besides, the High affinity of some benzodiazepines (e.g., midazolam) to α1 subunit of GABA-A receptor causes sedative, hypnotic, amnesic, and some antiepileptic effects; however, some other benzodiazepines (e.g., diazepam) have high affinity to α3 subunits, which causes anxiolytic, muscle relaxant, and strong antiepileptic effects. The CB1 receptor partial agonism effect of tetrahydrocannabinol has a sedative advantage over full agonism due to desensitization of CB1 receptors. Conclusion: From the molecular pharmacology prospect, it is possible to design new drugs with more specific CNS depressants effect and fewer side effects by targeting particular receptors with a precise reaction.