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Pharmacokinetics and pharmacodynamics of famotidine in children
L P James1, J D Marshall, M J Heulitt
1Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, USA.
Insights
This study investigated intravenous famotidine in children for stress ulcer prevention. Pediatric famotidine pharmacokinetics and pharmacodynamics are similar to adults, with no age-related differences observed.
Area of Science:
- Pharmacology
- Pediatric Gastroenterology
Background:
- Stress ulceration is a risk in critically ill children.
- Famotidine is used for stress ulcer prophylaxis.
Purpose of the Study:
- To evaluate the pharmacokinetics and pharmacodynamics of intravenous famotidine in pediatric patients.
- To compare pediatric famotidine parameters with adult data.
Main Methods:
- 12 children (1.1-12.9 years) received a 0.5-mg/kg intravenous famotidine infusion.
- Blood, urine samples, and intragastric pH were monitored.
- Pharmacokinetic parameters (Cmax, t1/2, Vdss, Cl, ClR, Fel) and pharmacodynamic parameters (EC50) were calculated.
Main Results:
- Mean Cmax: 527.6 ng/mL, t1/2: 3.2 hours, Vdss: 2.4 L/kg.
- Plasma clearance (Cl): 0.70 L/hr/kg, Renal clearance (ClR): 0.43 L/hr/kg.
- 73% of the dose excreted unchanged; EC50: 26.0 ng/mL. No significant age-related parameter differences were found.
Conclusions:
- Pediatric pharmacokinetics and pharmacodynamics of famotidine are comparable to adults.
- Famotidine efficacy is dependent on baseline intragastric pH.
Abstract:
The pharmacokinetics and pharmacodynamics of intravenous famotidine were studied in 12 children (1.1-12.9 years of age; mean weight +/- standard deviation = 27.6 +/- 21.2 kg) who were given the drug for prophylactic management of stress ulceration. After a 0.5-mg/kg infusion of famotidine, timed blood (n = 10) and urine (n = 6) samples and repeated evaluations of intragastric pH (n = 13) were obtained from each subject. Pharmacokinetic parameters were determined from curve fitting of serum concentration data. The mean (+/- SD) maximum serum concentration (Cmax) was 527.6 +/- 281.2 ng/mL, the elimination half-life (t1/2) was 3.2 +/- 3.0 hours, and the apparent steady-state volume of distribution (Vdss) was 2.4 +/- 1.7 L/kg. Plasma clearance (Cl) and renal clearance (ClR) were 0.70 +/- 0.34 L/hr/kg and 0.43 +/- 0.24 L/hr/kg, respectively. Over 24 hours, 73.0 +/- 27.3% of the dose was excreted unchanged in the urine (Fel). Pharmacodynamic analysis of gastric pH data using the sigmoid Emax model predicted that 50% of the maximal effect of famotidine (EC50) occurs at a serum concentration of 26.0 +/- 13.2 ng/mL. Children who did not have an initial intragastric pH < or = 4 did not have a significant response in pH after receiving famotidine. Although Vdss and Cl were higher in these children than those seen in adults, statistically significant relationships between these parameters and age were not observed in the study population. The pharmacodynamics and pharmacokinetics of famotidine in children older than one year of age appear to be similar to those noted in adults.