Absorption of phenobarbital after the intramuscular administration of single doses in infants

Area of Science:

• Pharmacology
• Pediatric Medicine
• Clinical Pharmacy

Background:

• Phenobarbital is a widely used anticonvulsant medication.
• Understanding its pharmacokinetics in infants is crucial for safe and effective dosing.
• Intramuscular administration is a common route for medication delivery in pediatric care.

Purpose of the Study:

• To determine the blood concentration profile of phenobarbital after intramuscular administration in infants.
• To assess the time to reach peak serum concentrations.
• To compare blood phenobarbital levels with cerebrospinal fluid concentrations.

Main Methods:

• A single large dose of phenobarbital (approximately 10 mg/kg) was administered intramuscularly to 39 infants.
• Blood samples were collected at various time points to measure phenobarbital concentrations.
• Cerebrospinal fluid samples were analyzed in a subset of patients.

Main Results:

• Rapid absorption was observed, with mean blood phenobarbital concentrations reaching 9.30 mug/ml at 30 minutes and 12.76 mug/ml at 90 minutes.
• The mean peak blood concentration was 13.28 mug/ml, typically achieved within 2 hours post-injection.
• Cerebrospinal fluid phenobarbital concentrations averaged approximately 50% of concurrent blood concentrations.

Conclusions:

• Intramuscular administration of phenobarbital leads to rapid and significant blood level attainment in infants.
• The pharmacokinetic profile suggests efficient absorption via the intramuscular route in this population.
• The observed ratio of cerebrospinal fluid to blood concentrations has implications for phenobarbital's central nervous system penetration and therapeutic efficacy.