2.1 Recommended Dosage in Adults

The recommended dosage and duration of Famotidine for Oral Suspension in adults with normal renal function is shown in Table 1.

• After preparation, the concentration of Famotidine for Oral Suspension is 8 mg/mL [see Dosage and Administration (2.3)].

2.2 Recommended Dosage in Pediatric Patients

The recommended dosage and duration of Famotidine for Oral Suspension in pediatric patients with normal renal function is shown in Table 2.

• After preparation, the concentration of Famotidine for Oral Suspension is 8 mg/mL [see Dosage and Administration (2.3)].

2.3 Recommended Dosage in Adults with Renal Impairment

Recommended dosage adjustments for adults with moderate to severe renal impairment (creatinine clearance less than 60 mL/min) by indication are shown in Table 3. Use the lowest effective dosage [see Use in Specific Populations (8.6)].

A safe and effective dosage has not been established in pediatric patients with renal impairment.

2.4 Preparation and Administration Instructions

Preparation of Reconstituted Suspension by a Healthcare Provider Prior to Dispensing

• Prior to dispensing, constitute Famotidine for Oral Suspension by slowly adding 46 mL of purified water to the bottle.
• Shake vigorously for 5 to 10 seconds immediately after adding the water.
• The bottle of constituted suspension contains 55 mL (40 mg of famotidine per 5 mL), and should be an off-white, homogeneous suspension.

Administration and Storage of Constituted Suspension

• Shake the bottle of constituted Famotidine for Oral Suspension vigorously for 5 to 10 seconds prior to each use.
• Take Famotidine for Oral Suspension once daily before bedtime or twice daily in the morning and before bedtime, as recommended.
• Famotidine for Oral Suspension may be taken with or without food [see Clinical Pharmacology (12.3)].
• Famotidine for Oral Suspension may be given with antacids.
• Store the constituted suspension at 25°C (77°F); excursions permitted to 15°C to 30°C (59°F to 86°F) [see USP Controlled Room Temperature]. Protect from freezing. Discard unused constituted suspension after 30 days.

5.1 Central Nervous System Adverse Reactions

Central nervous system (CNS) adverse reactions, including confusion, delirium, hallucinations, disorientation, agitation, seizures, and lethargy, have been reported in elderly patients and patients with moderate and severe renal impairment treated with famotidine. Since famotidine blood levels are higher in patients with renal impairment than in patients with normal renal function, dosage adjustments are recommended in patients with renal impairment [see Dosage and Administration (2.2), Clinical Pharmacology (12.3)].

5.2 Concurrent Gastric Malignancy

In adults, symptomatic response to therapy with Famotidine for Oral Suspension does not preclude the presence of gastric malignancy. Consider evaluation for gastric malignancy in adult patients who have a suboptimal response or an early symptomatic relapse after completing treatment with Famotidine for Oral Suspension.

6.1 Clinical Trial Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

The safety of Famotidine for Oral Suspension has been established based on adequate and well-controlled studies of another oral famotidine product [see Clinical Studies (14)]. The following is a summary of the adverse reactions reported in those studies.

Oral famotidine was studied in 7 U.S. and international placebo- and active-controlled trials in approximately 2500 patients [see Clinical Studies (14)]. A total of 1442 patients were treated with famotidine, including 302 treated with 40 mg twice daily, 456 treated with 20 mg twice daily, 461 treated with 40 mg once daily, and 396 treated with 20 mg once daily. The population was 17 to 91 years old, fairly well distributed between sex and race; however, the predominant race was White.

The following adverse reactions occurred in greater than or equal to 1% of famotidine-treated patients: headache, dizziness and constipation.

The following other adverse reactions were reported in less than 1% of patients in clinical trials:

Body as a Whole: fever, asthenia, fatigue

Cardiovascular: palpitations

Gastrointestinal: elevated liver enzymes, vomiting, nausea, abdominal discomfort, anorexia, dry mouth

Hematologic: thrombocytopenia

Hypersensitivity: orbital edema, rash, conjunctival injection, bronchospasm

Musculoskeletal: musculoskeletal pain, arthralgia

Nervous System/Psychiatric: seizure, hallucinations, depression, anxiety, decreased libido, insomnia, somnolence

Skin: pruritus, dry skin, flushing

Special Senses: tinnitus, taste disorder

Other: impotence

Pediatric Patients Less Than 1 Year of Age

In a clinical study in 35 pediatric patients less than 1 year of age with GERD symptoms, two patients discontinued due to adverse reactions. Agitation observed in 5 patients resolved when famotidine was discontinued [see Use in Specific Populations (8.4)].

6.2 Postmarketing Experience

The following adverse reactions have been identified during post-approval use of famotidine. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Cardiovascular: arrhythmia, AV block, prolonged QT interval

Gastrointestinal: cholestatic jaundice, hepatitis

Hematologic: agranulocytosis, pancytopenia, leukopenia

Hypersensitivity: anaphylaxis, angioedema, facial edema, urticaria

Musculoskeletal: rhabdomyolysis, muscle cramps

Nervous System/Psychiatric: confusion, agitation, paresthesia

Respiratory: interstitial pneumonia

Skin: toxic epidermal necrolysis/Stevens-Johnson syndrome

7.1 Drugs Dependent on Gastric pH for Absorption

Famotidine can reduce the absorption of other drugs due to its effect on reducing intragastric acidity, leading to loss of efficacy of the concomitant drug.

Concomitant administration of Famotidine for Oral Suspension with dasatinib, delavirdine mesylate, cefditoren, and fosamprenavir is not recommended.

See the prescribing information for other drugs dependent on gastric pH for absorption for administration instructions, including atazanavir, erlotinib, ketoconazole, itraconazole, ledipasvir/sofosbuvir, nilotinib, and rilpivirine.

7.2 Tizanidine (CYP1A2 Substrate)

Although not studied clinically, famotidine is considered a weak CYP1A2 inhibitor and may lead to substantial increases in blood concentrations of tizanidine, a CYP1A2 substrate. Avoid concomitant use with Famotidine for Oral Suspension. If concomitant use is necessary, monitor for hypotension, bradycardia or excessive drowsiness. Refer to the full prescribing information for tizanidine.

8.1 Pregnancy

Risk Summary

Available data with H2-receptor antagonists, including famotidine, in pregnant women are insufficient to establish a drug-associated risk of major birth defects, miscarriage or adverse maternal or fetal outcomes. In animal reproduction studies, no adverse development effects were observed with oral administration of famotidine at doses up to approximately 243 and 122 times, respectively, the recommended human dose of 80 mg/day for the treatment of erosive esophagitis (see Data).

The estimated background risk for major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively.

Data

Animal Data

Reproductive studies have been performed in rats and rabbits at oral doses of up to 2000 and 500 mg/kg/day, respectively, and in both species at intravenous doses of up to 200 mg/kg/day, and have revealed no significant evidence of impaired fertility or harm to the fetus due to famotidine. While no direct fetotoxic effects have been observed, sporadic abortions occurring only in mothers displaying marked decreased food intake were seen in some rabbits at oral doses of 200 mg/kg/day (about 49 times the recommended human dose of 80 mg/day, based on body surface area) or higher. There are, however, no adequate or well-controlled studies in pregnant women. Because animal reproductive studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed.

8.2 Lactation

Risk Summary

There are limited data available on the presence of famotidine in human breast milk. There were no effects on the breastfed infant. There are no data on famotidine effects on milk production. Famotidine is present in the milk of lactating rats (see Data).

The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for famotidine and any potential adverse effects on the breastfed child from Famotidine for Oral Suspension or from the underlying maternal condition.

Data

Animal Data

Transient growth depression was observed in young rats suckling from mothers treated with maternotoxic doses of famotidine at least 600 times the usual human dose.

8.4 Pediatric Use

Peptic Ulcer Disease and GERD With or Without Esophagitis and Ulcerations

Pediatric Patients 1 Year to Less Than 17 Years of Age

The safety and effectiveness of Famotidine for Oral Suspension have been established in pediatric patients 1 year to less than 17 years of age for the treatment of peptic ulcer disease and GERD with or without esophagitis and ulcerations. Use of Famotidine for Oral Suspension in this age group is supported by evidence from adequate and well-controlled studies of famotidine in adults with additional pharmacokinetic and pharmacodynamic data in pediatric patients 1 year to less than 17 years of age [see Dosage and Administration (2.2), Clinical Pharmacology (12.2, 12.3)]. The safety and effectiveness of Famotidine for Oral Suspension for the treatment of peptic ulcer disease in pediatric patients less than 1 year of age have not been established.

GERD

Pediatric Patients Less Than 1 Year of Age

The safety and effectiveness of Famotidine for Oral Suspension have been established in pediatric patients from birth to less than 1 year of age for the treatment of GERD. The use of Famotidine for Oral Suspension in this age group is supported by evidence from adequate and well-controlled studies of famotidine in adults and with supportive data in pediatric patients from birth to less than 1 year of age [see Dosage and Administration (2.2), Clinical Pharmacology (12.2, 12.3), Clinical Studies (14.7)].

Other Conditions

The safety and effectiveness for the treatment of pathological hypersecretory conditions and reduction of risk of DU recurrence have not been established in pediatric patients.

A safe and effective dosage has not been established in pediatric patients with renal impairment.

8.5 Geriatric Use

Of the 1442 famotidine-treated patients in clinical studies, approximately 10% were 65 and older. In these studies, no overall differences in safety or effectiveness were observed between elderly and younger patients. In postmarketing experience, CNS adverse reactions have been reported in elderly patients with and without renal impairment receiving famotidine [see Warnings and Precautions (5.1)].

Famotidine is known to be substantially excreted by the kidney, and the risk of adverse reactions to Famotidine for Oral Suspension may be greater in elderly patients, particularly those with impaired renal function [see Use in Specific Populations (8.6)].

In general, use the lowest effective dose of Famotidine for Oral Suspension for an elderly patient and monitor renal function [see Dosage and Administration (2.2)].

8.6 Renal Impairment

CNS adverse reactions and prolonged QT intervals have been reported in patients with moderate and severe renal impairment [see Warnings and Precautions (5.1)]. The clearance of famotidine is reduced in adults with moderate and severe renal impairment compared to adults with normal renal function [see Clinical Pharmacology (12.3)]. No dosage adjustment is needed in adults with mild renal impairment (creatinine clearance greater than or equal to 60 mL/min). Dosage reduction is recommended in adults with moderate or severe renal impairment (creatinine clearance less than 60 mL/min) [see Dosage and Administration (2.3)]. Data are not available to establish a safe and effective dosage in pediatric patients with renal impairment.

12.1 Mechanism of Action

Famotidine is a competitive inhibitor of H2-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.

12.2 Pharmacodynamics

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 1 hour; the maximum effect was dose-dependent, occurring within 1 to 3 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 a pH level of 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 Emax 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 4).

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.

12.3 Pharmacokinetics

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/min, 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, CLTotal was 0.13 ± 0.06 L/hr/kg, 0.21 ± 0.06 L/hr/kg, and 0.49 ± 0.17 L/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 pediatric patients 11 years to 15 years is compared to infants from birth to 12 months in Table 5.

Patients with Renal Impairment

In adult patients with severe renal impairment (creatinine clearance less than 30 mL/min), 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/min), 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 AUC0-10h of famotidine increased from 424 to 768 ng•hr/mL and the maximum serum concentration (Cmax) 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.

13.1 Carcinogenesis, 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/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/day) fertility and reproductive performance were not affected.

14.1 Active Duodenal Ulcer (DU)

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 6, 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.

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.

14.2 Active Gastric Ulcer (GU)

In both a U.S. and an international multicenter, double-blind trials in patients with endoscopically confirmed active 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 7, 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.

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).

14.3 Symptomatic 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 8, patients treated with famotidine 20 mg twice daily had greater improvement in symptomatic GERD than patients treated with 40 mg at bedtime or placebo.

14.4 Erosive Esophagitis Due to GERD

Healing of endoscopically verified erosion and symptomatic improvement were studied in a U.S. and an international double-blind trial. 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 showed a significantly greater percentage of healing of erosive esophagitis for famotidine 40 mg twice daily at Weeks 6 and 12 (Table 9).

As compared to placebo, patients in the U.S. trial who received famotidine had faster relief of daytime and nighttime heartburn, and a greater percentage of famotidine-treated patients experienced complete relief of nighttime heartburn. These differences were statistically significant.

In the international trial, when orally administered famotidine 40 mg twice daily was compared to orally administered ranitidine 150 mg twice daily, a statistically significantly greater percentage of healing of erosive esophagitis was observed with famotidine 40 mg twice daily at Week 12 (Table 10). There was, however, no significant difference in symptom relief among treatment groups.

14.5 Pathological Hypersecretory Conditions

In trials of patients with pathological hypersecretory conditions such as Zollinger-Ellison syndrome with or without multiple endocrine neoplasias, famotidine significantly inhibited gastric acid secretion and controlled associated symptoms. Orally administered famotidine dosages from 20 mg to 160 mg every 6 hours maintained basal acid secretion below 10 mEq/hr; initial dosages were titrated to the individual patient need and subsequent adjustments were necessary with time in some patients.

14.6 Risk Reduction of DU Recurrence

Two randomized, double-blind, multicenter trials in patients with endoscopically confirmed healed DUs demonstrated that patients receiving treatment with orally administered famotidine 20 mg at bedtime had lower rates of DU recurrence, as compared with placebo:

• In the U.S. trial, DU recurrence within 12 months was 2.4 times greater in patients treated with placebo than in the patients treated with famotidine. The 89 famotidine-treated patients had a cumulative observed DU recurrence rate of 23%, compared to a 57% in the 89 patients receiving placebo (p<0.01).
• In the international trial, the cumulative observed DU recurrence within 12 months in the 307 famotidine-treated patients was 36%, compared to 76% in the 325 patients who received placebo (p<0.01).

Controlled trials have not extended beyond 1 year.

14.7 GERD in Pediatric Patients Less Than 1 Year of Age

In a double-blind, randomized, treatment-withdrawal study, 35 pediatric patients less than 1 year of age who were diagnosed with GERD, primarily by history of vomiting (spitting up) and irritability (fussiness), were treated for up to 4 weeks with famotidine for oral suspension 0.5 mg/kg or 1 mg/kg administered once daily for patients less than 3 months of age and administered twice daily for patients 3 months to less than 12 months of age. Caregivers were instructed to provide conservative treatment including thickened feedings. After 4 weeks of treatment, patients were randomly withdrawn from the treatment and followed an additional 4 weeks for vomiting (spitting up), irritability (fussiness) and global assessments of improvement. The study patients ranged in age at entry from 1.3 to 10.5 months (mean 5.6 ± 2.9 months), 57% were female, 91% were white and 6% were black. Most patients (27/35) continued into the treatment-withdrawal phase of the study. Most patients improved during the initial treatment phase of the study. Results of the treatment-withdrawal phase were difficult to interpret because of small numbers of patients.