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Bioavailability of intramuscular rocuronium in infants and children
1Department of Anesthesia, University of California, San Francisco 94143-0648, USA.
Insights
Intramuscular rocuronium in pediatric patients shows good bioavailability, with plasma concentrations peaking around 13 minutes after administration. This study quantifies the absorption rate and extent of rocuronium following intramuscular injection.
Area of Science:
- Pharmacology
- Anesthesiology
- Pediatric Medicine
Background:
- Rocuronium administered intramuscularly at specific doses achieves complete neuromuscular blockade in pediatric patients within minutes.
- Understanding the pharmacokinetic profile of intramuscular rocuronium is crucial for optimizing its clinical use in children.
Purpose of the Study:
- To determine the rate and extent of rocuronium absorption after intramuscular administration in pediatric patients.
- To analyze plasma concentrations (Cp) of rocuronium following both intramuscular and intravenous administration.
Main Methods:
- Twenty-nine pediatric patients (3 months to 5 years) received anesthesia with N2O and halothane.
- Rocuronium was administered intramuscularly (deltoid) or intravenously at doses of 1,000 µg/kg (infants) or 1,800 µg/kg (children).
- Plasma samples were collected 2-240 minutes post-administration, and pharmacokinetic analysis was performed.
Main Results:
- Intramuscular rocuronium demonstrated an average bioavailability of 82.6% with an absorption rate constant of 0.105 min⁻¹.
- Simulations predicted peak plasma concentrations (Cp) at approximately 13 minutes post-intramuscular injection.
- Less than 4% of the intramuscular dose remained unabsorbed 30 minutes after administration.
Conclusions:
- Rocuronium administered into the deltoid muscle results in peak plasma concentrations around 13 minutes.
- Approximately 80% of the systemically administered intramuscular rocuronium dose is absorbed.
Background:
Intramuscular rocuronium, in doses of 1,000 microg/kg in infants and 1,800 microg/kg in children, produces complete twitch depression in 5-6 min. To determine the rate and extent of absorption of rocuronium after intramuscular administration, blood was sampled at various intervals after rocuronium administration by both intramuscular and intravenous routes to determine plasma concentrations (Cp) of rocuronium.
Methods:
Twenty-nine pediatric patients ages 3 months to 5 yr were anesthetized with N2O and halothane. The trachea was intubated, ventilation was controlled, and adductor pollicis twitch tension was measured. When anesthetic conditions were stable, rocuronium (1,000 microg/kg for infants and 1,800 microg/kg for children) was injected either intramuscularly (in the deltoid muscle) or intravenously. Four venous plasma samples were obtained from each child 2-240 min after rocuronium administration. A mixed-effects population pharmacokinetic analysis was applied to these values to determine bioavailability, absorption rate constant, and time to peak Cp with intramuscular administration.
Results:
With intramuscular administration, rocuronium's bioavailability averaged 82.6% and its absorption rate constant was 0.105 min(-1). Simulation indicated that Cp peaked 13 min after rocuronium was given intramuscularly, and that 30 min after intramuscular administration, less than 4% of the administered dose remained to be absorbed from the intramuscular depot.
Conclusions:
After rocuronium is administered into the deltoid muscle, plasma concentrations peak at 13 min, and approximately 80% of the administered drug is absorbed systemically.