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 tablets. 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)].
In adults, symptomatic response to therapy with famotidine tablets 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 tablets.
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 tablets was studied in 7 US and international placebo- and active-controlled trials in approximately 2500 patients
[see Clinical Studies (
. A total of 1442 patients were treated with famotidine tablets, 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 17-91 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 tablets-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
Gastrointestinal: elevated liver enzymes, vomiting, nausea, abdominal discomfort, anorexia, dry mouth
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
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
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 tablets 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.
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 tablets. If concomitant use is necessary, monitor for hypotension, bradycardia or excessive drowsiness. Refer to the full prescribing information for tizanidine.
Available data with H
2 -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 per day for the treatment of erosive esophagitis
(se e 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.
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 tablets. 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 per 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.
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
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 tablets or from the underlying maternal condition.
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.
The safety and effectiveness of famotidine tablets 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 tablets and the recommended dosage of famotidine tablets in these pediatric patients is supported by evidence from adequate and well-controlled studies of famotidine tablets in adults and published pharmacokinetic and pharmacodynamic data in pediatric patients [s ee 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 (
. For pediatric patients weighing less than 40 kg, consider another famotidine formulation (e.g., oral suspension, lower dose tablet).
Of the 1442 famotidine tablets-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 tablets [ see Warnings and Precautions ( 5.1)] .
Famotidine is known to be substantially excreted by the kidney, and the risk of adverse reactions to famotidine tablets may be greater in elderly patients, particularly those with impaired renal function
[ see Use in Specific Populations (
In general, use the lowest effective dose of famotidine tablets for an elderly patient and monitor renal function
[see Dosage and Administration (
CNS adverse reactions and prolonged QT intervals have been reported in patients with moderate and severe renal impairment
[see Warnings and Precautions (
The clearance of famotidine is reduced in adults with moderate and severe renal impairment compared to adults with normal renal function
[see Clinical Pharmacology (
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 (
The types of adverse reactions in overdosage of famotidine tablets are similar to the adverse reactions encountered with use of recommended dosages [ see Adverse Reactions ( 6.1)] .
In the event of overdosage, treatment should be symptomatic and supportive. Unabsorbed material should be removed from the gastrointestinal tract, the patient should be monitored, and supportive therapy should be employed.
Due to low binding to plasma proteins, famotidine is eliminated by hemodialysis. There is limited experience on the usefulness of hemodialysis as a treatment for famotidine tablets overdosage.
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