FAMOTIDINE 40 mg/5mL Powder, For Suspension, 50 mL — NDC 31722-063-31 (Billing 31722-0063-31)

12 CLINICAL PHARMACOLOGY

12.1Mechanism of Action Famotidine is a competitive inhibitor of histamine-2 (H 2 ) receptors. The primary clinically important pharmacologic activity of famotidine is inhibition of gastric secretion. Both the acid concentration and volume of gastric secretion are suppressed by famotidine, while changes in pepsin secretion are proportional to volume output.

12.2Pharmacodynamics Adults Famotidine inhibited both basal and nocturnal gastric secretion, as well as secretion stimulated by food and pentagastrin. After oral administration of famotidine, the onset of the antisecretory effect occurred within one hour; the maximum effect was dose-dependent, occurring within one to three hours. Duration of inhibition of secretion by doses of 20 mg and 40 mg was 10 to 12 hours.

Single evening oral doses of 20 mg and 40 mg inhibited basal and nocturnal acid secretion in all subjects; mean nocturnal gastric acid secretion was inhibited by 86% and 94%, respectively, for a period of at least 10 hours. The same doses given in the morning suppressed food-stimulated acid secretion in all subjects. The mean suppression was 76% and 84%, respectively, 3 to 5 hours after administration, and 25% and 30%, respectively, 8 to 10 hours after administration.

In some subjects who received the 20 mg dose, however, the antisecretory effect was dissipated within 6 to 8 hours. There was no cumulative effect with repeated doses. The nocturnal intragastric pH was raised by evening doses of 20 mg and 40 mg of famotidine to mean values of 5.0 and 6.4, respectively.

When famotidine was given after breakfast, the basal daytime interdigestive pH at 3 and 8 hours after 20 mg or 40 mg of famotidine was raised to about 5. Famotidine had little or no effect on fasting or postprandial serum gastrin levels. Gastric emptying and exocrine pancreatic function were not affected by famotidine.

In clinical pharmacology studies, systemic effects of famotidine in the CNS, cardiovascular, respiratory or endocrine systems were not noted. Also, no anti-androgenic effects were noted. Serum hormone levels, including prolactin, cortisol, thyroxine (T4), and testosterone, were not altered after treatment with famotidine.

Pediatric Patients Pharmacodynamics of famotidine, assessed by gastric pH, were evaluated in 5 pediatric patients 2 years to 13 years of age using the sigmoid E max model. These data suggest that the relationship between serum concentration of famotidine and gastric acid suppression is similar to that observed in adults (see Table 3). Table 3: Serum Concentrations of Famotidine Associated with Gastric Acid Reduction in Famotidine-Treated Pediatric and Adult Patients a EC 50 (ng/mL) a Pediatric Patients 26 ± 13 Adults Healthy adult subjects 26.5 ±

10.3Adult patients with upper GI bleeding 18.7 ± 10.8 a Using the Sigmoid E max model, serum concentrations of famotidine associated with 50% maximum gastric acid reduction are presented as means ± SD. In a study examining the effect of famotidine on gastric pH and duration of acid suppression in pediatric patients, four pediatric patients ages 11 to 15 years of age using the oral formulation at a dose of 0.5 mg/kg, maintained a gastric pH above 5 for 13.5 ± 1.8 hours.

12.3Pharmacokinetics Absorption Famotidine is incompletely absorbed. The bioavailability of oral doses is 40 to 45%. Bioavailability may be slightly increased by food, or slightly decreased by antacids; however, these effects are of no clinical consequence.

Peak famotidine plasma levels occur in 1 to 3 hours. Plasma levels after multiple dosages are similar to those after single doses. Distribution Fifteen to 20% of famotidine in plasma is protein bound.

Elimination Metabolism Famotidine undergoes minimal first-pass metabolism. Twenty-five to 30% of an oral dose was recovered in the urine as unchanged compound. The only metabolite identified in humans is the S-oxide.

Excretion Famotidine has an elimination half-life of 2.5 to 3.5 hours.… [Excerpted — this section continues on DailyMed.]

12.1Mechanism of Action Famotidine is a competitive inhibitor of histamine-2 (H 2 ) receptors. The primary clinically important pharmacologic activity of famotidine is inhibition of gastric secretion. Both the acid concentration and volume of gastric secretion are suppressed by famotidine, while changes in pepsin secretion are proportional to volume output.

12.3Pharmacokinetics Absorption Famotidine is incompletely absorbed. The bioavailability of oral doses is 40 to 45%. Bioavailability may be slightly increased by food, or slightly decreased by antacids; however, these effects are of no clinical consequence.

Peak famotidine plasma levels occur in 1 to 3 hours. Plasma levels after multiple dosages are similar to those after single doses. Distribution Fifteen to 20% of famotidine in plasma is protein bound.

Elimination Metabolism Famotidine undergoes minimal first-pass metabolism. Twenty-five to 30% of an oral dose was recovered in the urine as unchanged compound. The only metabolite identified in humans is the S-oxide.

Excretion Famotidine has an elimination half-life of 2.5 to 3.5 hours. Famotidine is eliminated by renal (65 to 70%) and metabolic (30 to 35%) routes. Renal clearance is 250 to 450 mL/minute, indicating some tubular excretion.

Specific Populations Pediatric Patients Infants from birth to 12 Months After a single oral dose administration of 0.5 mg/kg orally in patients from birth to 12 months, the bioavailability is approximately 42%. The AUC increased 1.4-fold after single oral dose of 1 mg/kg compared to 0.5 mg/kg and 2.7-fold after multiple oral doses of 1 mg/kg compared to 0.5 mg/kg. Plasma clearance is reduced and elimination half-life is prolonged in pediatric patients from birth to 3 months of age compared to older pediatric patients.

Following intravenous administration of 0.5 mg/kg, CL Total was 0.13 ±

0.06L/hr/kg, 0.21 ±

0.06L/hr/kg, and 0.49 ±

0.17L/hr/kg in pediatric patients <1 month of age, <3 months of age, and >3 to 12 months of age, respectively. Elimination half-life was 10.5 hours, 8.1 hours, and 4.5 hours in pediatric patients <1 month of age, <3 months of age, and >3 to 12 months of age, respectively. Patients 11 Years to 15 Years The mean bioavailability in 8 pediatric patients was 50% compared to adult values of 42% to 49%.

Pharmacokinetic parameters in pediatrics 11 years to 15 years is compared to infants from birth to 12 months in Table 4. Table 4: Mean Pharmacokinetic Parameters Following a Single Oral Dose of 0.5 mg/kg in Infants and Pediatric Patients Infants from Birth to 12 Months (N=5) Pediatric Patients 11 Years to 15 Years (N=8) AUC 0-∞ (ng*hr/mL) a 645 ± 249 580 ± 60 C max (ng/mL) 79.2

97.3T max (hr) b 2.0 (1.0, 4.1) c 2.3 (2.1, 2.9) d T 1/2 (hr) 5.82 2.13 a arithmetic mean ± S.D. b median c observed minimum and maximum values d reported minimum and maximum values Patients with Renal Impairment In adult patients with severe renal impairment (creatinine clearance less than 30 mL/minute), the systemic exposure (AUC) of famotidine increased at least 5-fold. In adult patients with moderate renal impairment (creatinine clearance between 30 to 60 mL/minute), the AUC of famotidine increased at least 2-fold [see Dosage and Administration (2.3) , Use in Specific Populations (8.6) ].

Drug Interaction Studies Human Organic Anion Transporter (OAT) 1 and 3: In vitro studies indicate that famotidine is a substrate for OAT1 and OAT3. Following coadministration of probenecid (1500 mg), an inhibitor of OAT1 and OAT3, with a single oral 20 mg dose of famotidine in 8 healthy subjects, the serum AUC 0 to 10h of famotidine increased from 424 to 768 ng.hr/mL and the maximum serum concentration (C max ) increased from 73 to 113 ng/mL. Renal clearance, urinary excretion rate and amount of famotidine excreted unchanged in urine were decreased.

The clinical relevance of this interaction is unknown. Multidrug and Toxin Extrusion Protein 1 (MATE-1): An in vitro study showed that famotidine is an inhibitor of MATE-1. However, no clinically significant interaction with metformin, a substrate for MATE-1, was observed.

CYP1A2 : Famotidine is a weak CYP1A2 inhibitor.

12.2Pharmacodynamics Adults Famotidine inhibited both basal and nocturnal gastric secretion, as well as secretion stimulated by food and pentagastrin. After oral administration of famotidine, the onset of the antisecretory effect occurred within one hour; the maximum effect was dose-dependent, occurring within one to three hours. Duration of inhibition of secretion by doses of 20 mg and 40 mg was 10 to 12 hours.

Single evening oral doses of 20 mg and 40 mg inhibited basal and nocturnal acid secretion in all subjects; mean nocturnal gastric acid secretion was inhibited by 86% and 94%, respectively, for a period of at least 10 hours. The same doses given in the morning suppressed food-stimulated acid secretion in all subjects. The mean suppression was 76% and 84%, respectively, 3 to 5 hours after administration, and 25% and 30%, respectively, 8 to 10 hours after administration.

In some subjects who received the 20 mg dose, however, the antisecretory effect was dissipated within 6 to 8 hours. There was no cumulative effect with repeated doses. The nocturnal intragastric pH was raised by evening doses of 20 mg and 40 mg of famotidine to mean values of 5.0 and 6.4, respectively.

When famotidine was given after breakfast, the basal daytime interdigestive pH at 3 and 8 hours after 20 mg or 40 mg of famotidine was raised to about 5. Famotidine had little or no effect on fasting or postprandial serum gastrin levels. Gastric emptying and exocrine pancreatic function were not affected by famotidine.

In clinical pharmacology studies, systemic effects of famotidine in the CNS, cardiovascular, respiratory or endocrine systems were not noted. Also, no anti-androgenic effects were noted. Serum hormone levels, including prolactin, cortisol, thyroxine (T4), and testosterone, were not altered after treatment with famotidine.

Pediatric Patients Pharmacodynamics of famotidine, assessed by gastric pH, were evaluated in 5 pediatric patients 2 years to 13 years of age using the sigmoid E max model. These data suggest that the relationship between serum concentration of famotidine and gastric acid suppression is similar to that observed in adults (see Table 3). Table 3: Serum Concentrations of Famotidine Associated with Gastric Acid Reduction in Famotidine-Treated Pediatric and Adult Patients a EC 50 (ng/mL) a Pediatric Patients 26 ± 13 Adults Healthy adult subjects 26.5 ±

10.3Adult patients with upper GI bleeding 18.7 ± 10.8 a Using the Sigmoid E max model, serum concentrations of famotidine associated with 50% maximum gastric acid reduction are presented as means ± SD. In a study examining the effect of famotidine on gastric pH and duration of acid suppression in pediatric patients, four pediatric patients ages 11 to 15 years of age using the oral formulation at a dose of 0.5 mg/kg, maintained a gastric pH above 5 for 13.5 ± 1.8 hours.

14 CLINICAL STUDIES The safety and effectiveness of famotidine for oral suspension have been established based on adequate and well-controlled studies of another oral famotidine product. The following is a summary of the efficacy results reported in those studies.

14.1Active Duodenal Ulcer In a U.S. multicenter, double-blind trial in adult outpatients with endoscopically confirmed duodenal ulcer (DU), orally administered famotidine was compared to placebo. As shown in Table 4, 70% of patients treated with famotidine 40 mg at bedtime were healed by Week 4. Most patients’ DU healed within 4 weeks.

Patients not healed by Week 4 were continued in the trial. By Week 8, 83% of patients treated with famotidine had healed DU, compared to 45% of patients treated with placebo. The incidence of DU healing with famotidine was greater than with placebo at each time point based on proportion of endoscopically confirmed healed DUs.

Trials have not assessed the safety of famotidine in uncomplicated active DU for periods of more than 8 weeks. Table 4: Patients with Endoscopically Confirmed Healed Duodenal Ulcers Famotidine 40 mg at bedtime (N=89) Famotidine 20 mg twice daily (N=84) Placebo at bedtime (N=97) Week 2 32% a 38% a 17% Week 4 70% a 67% a 31% a p<0.001 vs. placebo In this study, time to relief of daytime and nocturnal pain was shorter for patients receiving famotidine than for patients receiving placebo; patients receiving famotidine also took less antacid than patients receiving placebo.

14.2Active Gastric Ulcer In both a U.S. and an international multicenter, double-blind trials in patients with endoscopically confirmed active gastric ulcer (GU), orally administered famotidine 40 mg at bedtime was compared to placebo. Antacids were permitted during the trials, but consumption was not significantly different between the famotidine and placebo groups. As shown in Table 5, the incidence of GU healing confirmed by endoscopy (dropouts counted as unhealed) with famotidine was greater than placebo at Weeks 6 and 8 in the U.S. trial, and at Weeks 4, 6 and 8 in the international trial.

In these trials, most famotidine-treated patients healed within 6 weeks. Trials have not assessed the safety of famotidine in uncomplicated active GU for periods of more than 8 weeks. Table 5: Patients with Endoscopically Confirmed Healed Gastric Ulcers U.S.

Study (N=149) International Study (N=294) Famotidine 40 mg at bedtime (N=74) Placebo at bedtime (N=75) Famotidine 40 mg at bedtime (N=149) Placebo at bedtime (N=145) Week 4 45% 39% 47% a 31% Week 6 66% a 44% 65% a 46% Week 8 78% b 64% 80% a 54% a p≤0.01 vs. placebo b p≤0.05 vs. placebo Time to complete relief of daytime and nighttime pain was statistically significantly shorter for patients receiving famotidine than for patients receiving placebo; however, neither trial demonstrated a statistically significant difference in the proportion of patients whose pain was relieved by the end of the trial (Week 8).

14.3Symptomatic Gastroesophageal Reflux Disease (GERD) Orally administered famotidine was compared to placebo in a U.S. trial that enrolled patients with symptoms of GERD and without endoscopic evidence of esophageal erosion or ulceration. As shown in Table 6, patients treated with famotidine 20 mg twice daily had greater improvement in symptomatic GERD than patients treated with 40 mg at bedtime or placebo. Table 6: Patients with Improvement of Symptomatic GERD (N=376) Famotidine 20 mg twice daily (N=154) Famotidine 40 mg at bedtime (N=149) Placebo at bedtime (N=73) Week 6 82% a 69% 62% a p≤0.01 vs. placebo

14.4Erosive Esophagitis due to GERD Healing of endoscopically verified erosion and symptomatic improvement were studied in a U.S. and an international double-blind trials. Healing was defined as complete resolution of all erosions visible with endoscopy. The U.S. trial comparing orally administered famotidine 40 mg twice daily to placebo and orally administered famotidine 20 mg twice daily show… [Excerpted — this section continues on DailyMed.]

13 NONCLINICAL TOXICOLOGY

13.1Carcinogenesis, Mutagenesis, Impairment Of Fertility Carcinogenic potential of famotidine was assessed in a 106-week oral carcinogenicity study in rats and a 92-week oral carcinogenicity study in mice. In the 106-week study in rats and the 92-week study in mice at oral doses of up to 2000 mg/kg/day (approximately 243 and 122 times, respectively, based on body surface area, the recommended human dose of 80 mg per day for the treatment of erosive esophagitis), there was no evidence of carcinogenic potential for famotidine.

Famotidine was negative in the microbial mutagen test (Ames test) using Salmonella typhimurium and Escherichia coli with or without rat liver enzyme activation at concentrations up to 10,000 mcg/plate. In in vivo studies in mice, with a micronucleus test and a chromosomal aberration test, no evidence of a mutagenic effect was observed. In studies with rats given oral doses of up to 2000 mg/kg/day (approximately 243 times, based on body surface area, the recommended human dose of 80 mg per day) fertility and reproductive performance were not affected.