Use of midazolam hydrochloride in anesthesia

The chemistry, pharmacology, pharmacokinetics, clinical efficacy, adverse effects, drug interactions, dosage, and cost and availability of midazolam hydrochloride are reviewed. The anxiolytic, sedative, hypnotic, anticonvulsant, muscle-relaxant, and amnesic properties of midazolam are similar to those of other injectable benzodiazepines. Midazolam is approximately two to four times as potent as diazepam. Midazolam hydrochloride is water soluble (resulting in fewer local adverse reactions after injection), has a rapid onset and short duration of action, and causes relatively mild cardiovascular and respiratory effects. The drug generally is well tolerated. Midazolam is a good premedicant for general or regional anesthesia. Its greatest use will probably be for conscious sedation during surgical or diagnostic procedures performed under local or regional anesthesia. Induction of anesthesia with midazolam alone is somewhat unpredictable; opiate pretreatment makes induction more consistent. Midazolam is a less reliable induction agent than thiopental, but because it produces fewer adverse cardiovascular and respiratory effects than thiopental, midazolam appears to be a safer induction agent for elderly patients or patients with cardiovascular disease. The recommended dose of midazolam for preoperative sedation is 0.07-0.1 mg/kg given by intramuscular injection one hour before surgery. For conscious sedation, 0.1-0.15 mg/kg intravenously in divided doses is usually adequate. Lower doses of midazolam are recommended for elderly or debilitated patients and patients who have severe liver disease. The costs of equipotent doses of midazolam and injectable diazepam are similar. An oral dosage form is under investigation in the United States. Midazolam's pharmacologic and pharmacokinetic profile makes it an attractive alternative to other injectable benzodiazepines used in anesthesia.