What Factors Affect Midazolam Dosage?

Midazolam is an extremely potent and fast-acting benzodiazepine medication. Due to its extremely short half life within the body, it is not typically used as a treatment for clinical anxiety disorders as are most other benzodiazepine drugs. Midazolam is instead typically used for procedural sedation, pre-operative sedation and general anesthesia, particularly when the drug's side effect of anteretrograde amnesia is desired. Occasionally, the medication is used as an acute treatment for seizures in pediatric patients in the place of rectally administered diazepam. Each of these applications demand the administration of a different midazolam dosage, with additional adjustments required according to the patient's age, renal health, level of hepatic function, debility, susceptibility to respiratory depression, and existing drug regimen.

Adult patients that require pre-operative sedation should receive midazolam as an intramuscular injection of between 0.07 and 0.08 mg per 2.2 lbs (1 kg) of body weight approximately one hour prior to surgery. If the surgical procedure requires conscious sedation and the patient is receiving no other central nervous system depressants as pre-medication, then the appropriate midazolam dosage is between 1.0 and 2.5 mg intravenously over two minutes in a 1 mg/mL dilution in adults. The dose may be increased in 5.0 mg increments every two minutes or more.

Pediatric patients require a significantly lower midazolam dosage. An initial intramuscular injection for pre-operative sedation should be between 0.1 and 0.15 mg per 2.2 lbs (1 kg) of body weight, not to exceed 10 mg except in unique circumstances and with close monitoring. Pre-operative sedative doses have been given up to 0.5 mg per kg.

Patients between the ages of six and 12 who are receiving the drug to induce conscious sedation should receive an intravenous midazolam dosage of 0.025 to 0.05 mg per 2.2 lbs (1 kg) of weight up to a maximum 0.4 mg per 2.2 lbs (1 kg), or 10 mg in total. Those between six months and six years should instead be given 0.05 to 0.1 mg per 2.2 lbs (1 kg), up to a maximum of 0.6 mg per 2.2 lbs (1 kg), or 6 mg in total. Patients under six months of age should be given midazolam cautiously, starting with a low midazolam dosage, adjusting it carefully to achieve the desired level of sedation. Premature infants should not be given this medication intravenously, as this form of the medication contains benzyl alcohol, associated with fatal “gasping syndrome” in this population.

The dosage may need to be adjusted to accommodate patients with an impairment of renal function, as this may extend the half life of midazolam in the body, increasing the time required for recovery. Patients with diminished levels of hepatic function will require lower doses. As a consequence, it is essential that these patients receive an extremely low dose initially, with dosage only cautiously increased under close monitoring.