Butabarbital

What it isAn intermediate-acting barbiturate sedative-hypnotic acting as a GABA-A positive allosteric modulator.

Why this oneIt survives as one of the last oral barbiturate hypnotics on the US market, where nearly all of that class has been retired.

What limits itTolerance develops within weeks, withdrawal can be life-threatening, and CYP induction plus a narrow therapeutic index make it a poor choice against modern hypnotics.