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Pepcid

Clinical Pharmacology
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Clinical Pharmacology

Pepcid

In studies of patients with pathological hypersecretory conditions such as Zollinger-Ellison Syndrome with or without multiple endocrine adenomas, PEPCID significantly inhibited gastric acid secretion and controlled associated symptoms. Orally administered doses from 20 to 160 mg q 6 h maintained basal acid secretion below 10 mEq/hr; initial doses were titrated to the individual patient need and subsequent adjustments were necessary with time in some patients. PEPCID was well tolerated at these high dose levels for prolonged periods (greater than 12 months) in eight patients, and there were no cases reported of gynecomastia, increased prolactin levels, or impotence which were considered to be due to the drug.

In Pediatric Patients

Pharmacokinetics

Table 6 presents pharmacokinetic data from clinical trials and a published study in pediatric patients ( < 1 year of age; N=27) given famotidine I.V. 0.5 mg/kg and from published studies of small numbers of pediatric patients (1-15 years of age) given famotidine intravenously. Areas under the curve (AUCs) are normalized to a dose of 0.5 mg/kg I.V. for pediatric patients 1-15 years of age and compared with an extrapolated 40 mg intravenous dose in adults (extrapolation based on results obtained with a 20 mg I.V. adult dose).

Table 6
Pharmacokinetic Parametersa of Intravenous Famotidine


Age
(N=number
of patients)		 Area Under
the Curve (AUC)
(ng-hr/mL)		 Total
Clearance (Cl)
(L/hr/kg)		 Volume of
Distribution (Vd)
(L/kg)		 Elimination
Half-life (T½)
(hours)
0-1 monthc(N=10) NA 0.13 ± 0.06 1.4 ± 0.4 10.5 ± 5.4
0-3 monthsd(N=6) 2688 ± 847 0.21 ± 0.06 1.8 ± 0.3 8.1 ± 3.5
> 3–12 monthsd(N=11) 1160 ± 474 0.49 ± 0.17 2.3 ± 0.7 4.5 ± 1.1
1-11 yrs (N=20) 1089 ± 834 0.54 ± 0.34 2.07 ± 1.49 3.38 ± 2.60
11-15 yrs (N=6) 1140 ± 320 0.48 ± 0.14 1.5 ± 0.4 2.3 ± 0.4
Adult (N=16) 1726b 0.39 ± 0.14 1.3 ± 0.2 2.83 ± 0.99
a Values are presented as means ± SD unless indicated otherwise.
b Mean value only.
c Single center study.
d Multicenter study.

Plasma clearance is reduced and elimination half-life is prolonged in pediatric patients 0-3 months of age compared to older pediatric patients. The pharmacokinetic parameters for pediatric patients, ages > 3 months-15 years, are comparable to those obtained for adults.

Bioavailability studies of 8 pediatric patients (11-15 years of age) showed a mean oral bioavailability of 0.5 compared to adult values of 0.42 to 0.49. Oral doses of 0.5 mg/kg achieved AUCs of 645 ± 249 ng-hr/mL and 580 ± 60 ng-hr/mL in pediatric patients < 1 year of age (N=5) and in pediatric patients 11-15 years of age, respectively, compared to 482 ± 181 ng-hr/mL in adults treated with 40 mg orally.

Pharmacodynamics

Pharmacodynamics of famotidine were evaluated in 5 pediatric patients 2-13 years of age using the sigmoid Emax model. These data suggest that the relationship between serum concentration of famotidine and gastric acid suppression is similar to that observed in one study of adults (Table 7).

Table 7
Pharmacodynamics of famotidine using the sigmoid Emax model


  EC50(ng/mL)*
Pediatric Patients 26 ± 13
Data from one study
a) healthy adult subjects 26.5 ± 10.3
b) adult patients with upper GI bleeding 18.7 ± 10.8
*Serum concentration of famotidine associated with 50% maximum gastric acid reduction. Values are presented as means ± SD.
Brand Name: Pepcid
Generic Name: Famotidine
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