Methohexital: a practical review for outpatient dental anesthesia.

Methohexital is an ultrashort-acting barbiturate widely used in dentistry because of its rapid onset, predictable effects, and short duration of action. Like other barbiturates, methohexital exerts its effects through the gamma-aminobutyric acid (GABA) receptor complex. By binding to its own receptor on the complex, methohexital augments the inhibitory effect of GABA on neurons and additionally can exert a similar effect independent of GABA. After intravenous injection, maximal brain concentrations are achieved within 30 sec and then quickly fall as the drug is redistributed to other tissues, yielding a duration of action after a single dose of 4 to 7 min. Hepatic metabolism accounts for elimination of the drug. Methohexital at conventional doses in healthy individuals is a mild respiratory depressant with modest cardiovascular effects. Adverse effects, however, can include apnea, cardiovascular depression, laryngospasm, hiccough, and allergic-like reactions. Although more recently introduced drugs, such as midazolam, etomidate, and propofol, have specific advantages, methohexital remains a drug of choice for dental outpatient anesthesia because of its low cost, rapid onset, short duration, lack of secretory or emetic properties, and proven history.