2.1 Recommended Dosage

Table 1 shows the recommended dosage of famotidine 20 mg and 40 mg tablets in adult and pediatric patients weighing 40 kg and greater with normal renal function. The use of famotidine 20 mg and 40 mg tablets is not recommended in pediatric patients weighing less than 40 kg because the lowest available strength (20 mg) exceeds the recommended dose for these patients. Use another famotidine formulation for pediatric patients weighing less than 40 kg.

2.2 Dosage in Renal Impairment

Dosage adjustments of famotidine tablets are recommended for patients with moderate to severe renal impairment (creatinine clearance less than 60 mL/min) [see Use in Specific Populations (8.6)]. Table 2 shows the recommended maximum dosage of famotidine 20 mg or 40 mg tablets for patients with renal impairment, by indication. Use the lowest effective dose. Some dosage adjustments may require switching to other formulations of famotidine (e.g., oral suspension, lower dose tablet).

2.3 Administration Instructions

• Take famotidine tablets once daily before bedtime or twice daily in the morning and before bedtime, as recommended.
• Famotidine tablets may be taken with or without food [see Clinical Pharmacology (12.3)].
• Famotidine tablets may be given with antacids.

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 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.

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.

Famotidine was studied in 7 U.S. and international placebo- and active-controlled trials in approximately 2,500 patients [see Clinical Studies (14)]. A total of 1,442 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 gender and race; however, the predominant race treated was Caucasian.

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

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 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. If concomitant use is necessary, monitor for hypotension, bradycardia or excessive drowsiness. Refer to the full prescribing information for tizanidine.

8.1 Pregnancy

8.2 Lactation

8.4 Pediatric Use

The safety and effectiveness of famotidine have been established in pediatric patients for the treatment of peptic ulcer disease (i.e., duodenal ulcer, gastric ulcer) and GERD (i.e., symptomatic nonerosive GERD, erosive esophagitis as diagnosed by endoscopy). The use of famotidine and the recommended dosage of famotidine in these pediatric patients is supported by evidence from adequate and well-controlled studies of famotidine in adults and published pharmacokinetic and pharmacodynamic data in pediatric patients [see Dosage and Administration (2.1), Clinical Pharmacology (12.2, 12.3)]. In pediatric patients, the safety and effectiveness for the treatment of pathological hypersecretory conditions and reduction of risk of duodenal ulcer recurrence have not been established.

Famotidine 20 and 40 mg tablets are not recommended for use in pediatric patients weighing less than 40 kg because these tablet strengths exceed the recommended dose for these patients [see Dosage and Administration (2.1)]. For pediatric patients weighing less than 40 kg, consider another famotidine formulation (e.g., oral suspension, lower dose tablet).

8.5 Geriatric Use

Of the 1,442 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 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 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 patients with mild renal impairment (creatinine clearance greater than or equal to 60 mL/minute). Dosage reduction is recommended in adult and pediatric patients greater than or equal to 40 kg with moderate or severe renal impairment (creatinine clearance less than 60 mL/minute) [see Dosage and Administration (2.2)].

12.1 Mechanism of Action

Famotidine is a competitive inhibitor of histamine-2 (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

12.3 Pharmacokinetics

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 2,000 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 2,000 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.

14.1 Active 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.

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

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.

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 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.

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 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 showed a significantly greater percentage of healing of erosive esophagitis for famotidine 40 mg twice daily at Weeks 6 and 12 (Table 7).

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 8). 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/hour; initial dosages were titrated to the individual patient need and subsequent adjustments were necessary with time in some patients.

14.6 Risk Reduction of Duodenal Ulcer 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 one year.

Storage

Store at 25°C (77°F); excursions permitted to 15° to 30°C (59° to 86°F) [see USP Controlled Room Temperature]. Dispense in a USP tight, light-resistant container.

Central Nervous System (CNS) Adverse Reactions Advise elderly patients and those with moderate and severe renal impairment of the risk of CNS adverse reactions, including confusion, delirium, hallucinations, disorientation, agitation, seizures, and lethargy [see Warnings and Precautions (5.1)]. Report symptoms immediately to a healthcare provider.

QT Prolongation Advise patients with moderate and severe renal impairment of the risk of QT interval prolongation [see Use in Specific Populations (8.6)]. Report new cardiac symptoms, such as palpitations, fainting and dizziness or lightheadedness immediately to a healthcare provider.

Administration

Advise patients:

• Take famotidine tablets once daily before bedtime or twice daily in the morning and before bedtime, as recommended.
• Famotidine tablets may be taken with or without food.
• Famotidine tablets may be given with antacids.