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Plasma concentration following oral and intramuscular atropine in children and their clinical effects
H W Gervais1, M el Gindi, P R Radermacher
1Department of Anaesthesiology, Johannes Gutenberg University Mainz, Germany.
Insights
Intramuscular atropine (20 mcg/kg) provided higher M2-cholinoceptor occupancy and antisialogogue effects in children compared to oral atropine (30 mcg/kg), indicating different potencies.
Area of Science:
- Pharmacology
- Pediatric Anesthesiology
Background:
- Atropine is commonly used for premedication in pediatric anesthesia.
- The efficacy of different administration routes (intramuscular vs. oral) and their corresponding plasma concentrations are not fully elucidated.
Purpose of the Study:
- To compare the efficacy of intramuscular (i.m.) versus oral atropine premedication in a pediatric population.
- To determine atropine plasma concentrations (APC) and M2-cholinoceptor occupancy following different administration routes.
- To assess the impact of atropine administration on heart rate, body temperature, and salivation.
Main Methods:
- A randomized controlled trial involving 45 children assigned to three groups: i.m. atropine (20 mcg/kg), oral atropine (30 mcg/kg), or no atropine.
- Measurements included atropine plasma concentrations (APC), M2-cholinoceptor occupancy, heart rate, rectal temperature, and salivation at various time points post-administration.
Main Results:
- Intramuscular atropine resulted in 60-70% M2-cholinoceptor occupancy peaking at 25 minutes, while oral atropine achieved only 10-20% occupancy peaking at 90 minutes.
- Antisialogogue effects were observed only with i.m. atropine.
- Heart rate changes and temperature variations were not significantly different from baseline across all groups.
Conclusions:
- A dosage of 30 mcg/kg oral atropine is not equipotent to 20 mcg/kg i.m. atropine in pediatric patients.
- Intramuscular administration leads to more rapid and sustained M2-cholinoceptor occupancy and superior antisialogogue effects.
Abstract:
In a paediatric population, we compared i.m. v oral atropine premedication to a control group without atropine and determined atropine plasma concentrations (APC). Forty-five children were randomly assigned to one of three groups. Group I received atropine, 20 micrograms.kg-1 i.m., 15 min prior to induction. Group II received atropine, 30 micrograms.kg-1 orally, group III received no atropine. APC (expressed as percent of muscarine-2 receptor subtype occupancy), heart rate, rectal temperature, and salivation were determined before atropine, and 15, 25, 45, 60, 90, 120 (no APC), and 150 min following atropine. Only 10-20% of the M2-cholinoceptors were occupied after oral atropine with a peak at 90 min compared to 60-70% occupancy with a peak 25 min after i.m. atropine. The peak in M2-cholinoceptor occupation in group I was paralleled by a peak percentage change in heart rate of 15% from baseline. The peak in receptor occupation in group II did not correspond to the peak increase in heart rate. The percentage change of heart rate over time was not significantly different from baseline values in any of the groups. Bradycardia or temperature changes did not occur in any of the groups. Antisialogogue effects were observed only in group I. We conclude that atropine; 30 micrograms.kg-1 orally is not an equipotent dosage to atropine, 20 micrograms.kg-1 i.m.