Which medication is likely to have the most sedative effect with rapidly increasing dosage?

Barbiturates are well-known for their potent sedative effects and the phenomenon of dose-dependent sedation. As the dosage of barbiturates increases, their sedative properties become more pronounced, leading to increased levels of drowsiness and lethargy. They work by enhancing the activity of the neurotransmitter gamma-aminobutyric acid (GABA) in the brain, which contributes to their sedative effects.

The rapidity of their action also allows for swift onset of sedation, particularly at higher doses, making them more likely than other medications listed to produce significant sedation with increasing doses. Barbiturates have a relatively narrow therapeutic window, meaning that as dosages increase, the risk of severe sedation and potential respiratory depression also rises sharply.