Midazolam IM Dosing for a 46.3 kg Patient
For a patient weighing 46.3 kg, the appropriate intramuscular midazolam dose is 0.07-0.08 mg/kg, which calculates to approximately 3.2-3.7 mg IM.
Dosing Calculation
The FDA-approved dosing for intramuscular midazolam follows a weight-based approach:
- Standard adult dosing (under 60 years): 0.07-0.08 mg/kg IM 1
- For a 46.3 kg patient: 46.3 kg × 0.07-0.08 mg/kg = 3.2-3.7 mg IM
This dose should be administered deep into a large muscle mass, with onset occurring within 15 minutes and peak effect at 30-60 minutes 1.
Important Considerations
Patient-Specific Factors
- Age: If the patient is over 60 years, reduce the dose by at least 20% (to approximately 2.6-3.0 mg) 2
- Respiratory status: Patients with chronic obstructive pulmonary disease require dose reduction 1
- Concomitant medications: If the patient is receiving opioids or other CNS depressants, reduce the dose due to synergistic effects 2, 1
Administration Guidelines
- Inject deep into a large muscle mass for optimal absorption 1
- Monitor for onset of action, which typically begins within 15 minutes 1
- Peak effect occurs at 30-60 minutes post-administration 1
- Duration of effect is approximately 30-60 minutes 2
Monitoring Requirements
- Continuous pulse oximetry is essential to monitor for respiratory depression 2
- Regular blood pressure measurements should be performed 2
- Assess respiratory rate and level of sedation frequently 2
- Have flumazenil available as a reversal agent in case of severe respiratory depression 2
Special Populations
Pediatric Patients
For pediatric patients, different dosing applies:
- Children 6 months to 5 years: 0.05-0.1 mg/kg IV 2, 3
- Children 6-12 years: 0.025-0.05 mg/kg IV 2, 3
- For preoperative sedation: 0.5-0.75 mg/kg (max 20 mg) 2
High-Risk Patients
- Elderly patients (>60 years): Reduce dose by at least 20% 2, 1
- Patients with hepatic or renal impairment: Reduced clearance requires lower dosing 2, 4
- Patients receiving concomitant opioids: Reduce dose due to increased risk of respiratory depression 2, 1
Safety Precautions
- The most serious adverse events include hypoventilation, decreased oxygen saturation, apnea, and hypotension 3
- Midazolam has a rapid onset but short duration of action compared to other benzodiazepines 4, 5
- Have reversal agents (flumazenil for benzodiazepines) immediately available 2
- Common side effects include hiccups, cough, nausea, and vomiting 4
By following these guidelines, midazolam can be safely administered intramuscularly to provide effective sedation, anxiolysis, and amnesia in appropriate clinical scenarios.