Aspiration prophylaxis in patients undergoing anesthesia (off-label use): Note: May be considered in patients at high risk for aspiration (Ref):
IV: 20 mg as a single dose ~40 to 90 minutes prior to induction of anesthesia; may be given with a rapid-acting nonparticulate antacid (eg, oral sodium citrate and citric acid) and/or metoclopramide (Ref).
Chronic spontaneous urticaria (alternative agent) (adjunct) (off-label use): Note: Use as additional therapy if insufficient response to full-dose H1 antihistamine.
Oral: 20 mg twice daily given in combination with H1 antihistamine; a trial of 2 to 4 weeks is suggested to assess response (Ref).
Gastroesophageal reflux disease, treatment:
Initial therapy:
Mild and intermittent symptoms (<2 episodes/week), and no evidence of erosive esophagitis: Note: For more severe or frequent initial symptoms, with or without evidence of erosive esophagitis, a proton pump inhibitor (PPI) as initial therapy is recommended.
Oral: 10 mg twice daily as needed; if symptoms persist after 2 to 4 weeks, increase to 20 mg twice daily for 2 weeks; if symptoms improve, may continue therapy as needed (Ref).
Note: If symptoms persist after 2 weeks of 20 mg twice daily, discontinue and consider PPI therapy (Ref).
Residual acid reflux symptoms despite maximal PPI therapy (adjunct): Oral: 20 mg once daily given at bedtime in addition to PPI therapy (Ref); may also administer famotidine intermittently or on demand with scheduled PPI (Ref).
OTC labeling (patient-guided therapy): Heartburn, mild intermittent symptoms: Oral: 10 to 20 mg up to twice daily when needed (maximum: 40 mg/day); may also be taken 10 to 60 minutes before meals or beverages that cause heartburn (maximum: 40 mg/day).
Infusion reaction, premedication (adjunct) (off-label use): IV, Oral: 20 mg typically administered 30 to 60 minutes prior to infusion of certain chemotherapy agents or biologics; usually given in conjunction with an H1 antihistamine (eg, diphenhydramine) and glucocorticoid (refer to institutional protocols) (Ref).
Mastocytosis (adjunct) (off-label use): Oral: 10 to 20 mg every 12 hours adjusted to achieve GI symptom relief. Typically used in combination with other appropriate agent(s) (eg, H1 antihistamine and/or leukotriene inhibitor) (Ref).
Stress ulcer prophylaxis in select critically ill patients (alternative agent) (off-label use): Note: Used as an alternative for proton pump inhibitors in critically ill patients with risk factors for GI bleeding (eg, coagulopathy, mechanical ventilation for >48 hours, traumatic brain injury, history of GI ulceration or bleeding within past year, extensive burns) (Ref).
Oral or via nasogastric (NG) tube (alternative to enteral PPI): 20 mg twice daily (Ref). Discontinue prophylaxis once risk factors have resolved (Ref).
IV: 20 mg twice daily (Ref). Discontinue prophylaxis once risk factors have resolved (Ref).
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
The renal dosing recommendations are based upon the best available evidence and clinical expertise. Senior Editorial Team: Bruce Mueller, PharmD, FCCP, FASN, FNKF; Jason Roberts, PhD, BPharm (Hons), B App Sc, FSHP, FISAC; Michael Heung, MD, MS.
Altered kidney function (Ref):
IV:
CrCl ≥50 mL/minute: No dosage adjustment necessary.
CrCl <50 mL/minute: Administer 50% of usual dose or continue usual dose but increase the dosing interval to every 36 to 48 hours.
Oral:
CrCl (mL/minute) |
If usual dose is 10 mg twice daily |
If usual dose is 20 mg once daily |
If usual dose is 20 mg twice daily |
---|---|---|---|
CrCl ≥60 |
No dosage adjustment necessary. |
No dosage adjustment necessary. |
No dosage adjustment necessary. |
CrCl 30 to <60 |
10 mg once daily or 20 mg every other day |
10 mg once daily or 20 mg every other day |
20 mg once daily or 40 mg every other day |
CrCl <30 |
10 mg every other day |
10 mg every other day |
10 mg once daily or 20 mg every other day |
Hemodialysis, intermittent (thrice weekly): Dialyzable (6% to 16%) (Ref):
IV, Oral: Dose as for CrCl <30 mL/minute; administer after hemodialysis on dialysis days. No supplemental dose necessary (Ref).
Peritoneal dialysis: Minimally dialyzed (5%) (Ref):
IV, Oral: Dose as for CrCl <30 mL/minute (Ref).
CRRT: Limited data utilizing hemofiltration rates of ≤1,800 mL/hour did not demonstrate a dose reduction is necessary (Saima 1990); however, no data regarding famotidine disposition utilizing contemporary flow rates of up to ~3,000 mL/hour are available:
IV, Oral: Dose as for CrCl <30 mL/minute (Ref).
PIRRT (eg, sustained, low-efficiency diafiltration):
IV, Oral: Dose as for CrCl <30 mL/minute; administer post-PIRRT session (Ref).
There are no dosage adjustments provided in the manufacturer's labeling.
(For additional information see "Famotidine: Pediatric drug information")
GERD:
Oral:
Suspension:
Infants <3 months: 0.5 mg/kg/dose once daily for up to 8 weeks; if not effective after 2 weeks, increasing to 1 mg/kg/dose once daily has been suggested (Ref)
Infants ≥3 months, Children, and Adolescents ≤16 years: Initial: 0.5 mg/kg/dose twice daily; maximum dose: 40 mg/dose; doses up to 1 mg/kg/dose twice daily have been reported (Ref)
Tablets: Children and Adolescents ≥40 kg: 20 mg twice daily for up to 6 weeks; for esophagitis and accompanying symptoms due to GERD, may use 20 to 40 mg twice daily for up to 12 weeks
IV:
Infants <3 months: Limited data available: 0.25 mg/kg/dose once daily; dosing based on a pharmacokinetic study which included 7 patients <3 months who received IV famotidine (Ref)
Infants ≥3 months: Limited data available: Initial: 0.25 mg/kg/dose every 12 hours; maximum dose: 20 mg/dose; dosing based on a pharmacokinetic study which included 11 patients >3 to 12 months who received IV famotidine (Ref)
Children and Adolescents: Initial: 0.25 mg/kg/dose every 12 hours; maximum dose: 20 mg/dose; doses up to 0.5 mg/kg/dose every 12 hours have been reported
Heartburn, acid indigestion, or sour stomach (OTC labeling): Children ≥12 years and Adolescents: Oral: 10 to 20 mg every 12 hours; dose may be taken 15 to 60 minutes before eating foods known to cause heartburn; maximum daily dose: 2 tablets/day (20 to 40 mg dependent upon OTC product)
Pathological hypersecretory conditions (eg, Zollinger-Ellison): Adolescents ≥17 years:
Oral: Initial: 20 mg every 6 hours, may increase up to 160 mg every 6 hours
IV: 20 mg every 12 hours
Peptic ulcer disease:
Oral:
Suspension: Children and Adolescents ≤16 years: 0.5 mg/kg/day at bedtime or divided twice daily; maximum daily dose: 40 mg/day; doses up to 1 mg/kg/day at bedtime or divided twice daily have been used
Tablets: Children and Adolescents >40 kg:
Duodenal ulcer: Acute therapy: 40 mg once daily at bedtime or 20 mg twice daily for 4 to 8 weeks
Gastric ulcer: Acute therapy: 40 mg once daily at bedtime for up to 8 weeks
IV: Children and Adolescents: Initial: 0.25 mg/kg/dose every 12 hours; maximum dose: 20 mg/dose; doses up to 0.5 mg/kg/dose every 12 hours have been reported
Stress ulcer prophylaxis, gastric acid suppression: Limited data available: Infants, Children, and Adolescents: IV: 1 to 2 mg/kg/day in divided doses every 8 to 12 hours; maximum daily dose: 40 mg/day (Ref)
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
Note: Dosing is based on pharmacokinetic parameters, limited pediatric studies, adult studies, and expert opinion (Ref).
Altered kidney function:
Weight-based dosing: Infants ≥3 months, Children, and Adolescents: IV, Oral:
CrCl |
Based on usual dose of 0.25 mg/kg/dose every 12 hours |
Based on usual dose of 0.5 mg/kg/dose every 12 hours |
---|---|---|
≥50 mL/minute/1.73 m2 |
No dosage adjustment necessary. |
No dosage adjustment necessary. |
10 to <50 mL/minute/1.73 m2 |
0.25 mg/kg/dose every 24 hours. Maximum dose: 10 mg/dose. |
0.5 mg/kg/dose every 24 hours. Maximum dose: 20 mg/dose. |
<10 mL/minute/1.73 m2 |
0.125 mg/kg/dose every 24 hours. Maximum dose: 5 mg/dose. |
0.25 mg/kg/dose every 24 hours. Maximum dose: 10 mg/dose. |
Fixed dosing: Children and Adolescents weighing ≥40 kg: Oral:
CrCl |
Based on usual dose of 10 mg twice daily |
Based on usual dose is 20 mg once daily |
Based on usual dose is 20 mg twice daily |
---|---|---|---|
CrCl ≥60 mL/minute/1.73 m2 |
No dosage adjustment necessary. |
No dosage adjustment necessary. |
No dosage adjustment necessary. |
CrCl 30 to <60 mL/minute/1.73 m2 |
10 mg once daily or 20 mg every other day |
10 mg once daily or 20 mg every other day |
20 mg once daily or 40 mg every other day |
CrCl <30 mL/minute/1.73 m2 |
10 mg every other day |
10 mg every other day |
10 mg once daily or 20 mg every other day |
Hemodialysis, intermittent (thrice weekly): Dialyzable (~6% to 16%):
Infants ≥3 months, Children, and Adolescents: IV, Oral: Dose as for CrCl <10 mL/minute/1.73 m2; administer after hemodialysis on hemodialysis days. No supplemental dose necessary.
Peritoneal dialysis: Minimally dialyzed (CAPD ~5%):
Infants ≥3 months, Children, and Adolescents: IV, Oral: Dose as for CrCl <10 mL/minute/1.73 m2.
CRRT: Note: Drug clearance is dependent on the effluent flow rate, filter type, and method of renal replacement. Recommendations are based on high-flux dialyzers and standard effluent flow rates of 25 to 40 mL/kg/hour (~2,000 to 3,000 mL/1.73 m2/hour).
Infants ≥3 months, Children, and Adolescents: IV, Oral: Dose as for CrCl 10 to <50 mL/minute/1.73 m2.
There are no dosage adjustments provided in the manufacturer's labeling.
Refer to adult dosing.
Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product
Solution, Intravenous:
Generic: 20 mg (50 mL); 40 mg/4 mL (4 mL); 200 mg/20 mL (20 mL)
Solution, Intravenous [preservative free]:
Generic: 20 mg/2 mL (2 mL)
Suspension Reconstituted, Oral:
Generic: 40 mg/5 mL (50 mL)
Tablet, Oral:
Acid Controller Original Str: 10 mg [DSC]
Acid Reducer: 10 mg [contains corn starch]
Famotidine Maximum Strength: 20 mg
Famotidine Orig St: 10 mg
Heartburn Relief: 10 mg
Heartburn Relief Max St: 20 mg
Pepcid: 20 mg, 40 mg [contains corn starch]
Pepcid AC Maximum Strength: 20 mg
Generic: 10 mg, 20 mg, 40 mg
Yes
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Solution, Intravenous:
Generic: 10 mg/mL (2 mL, 4 mL, 5 mL, 20 mL)
Tablet, Oral:
Generic: 20 mg, 40 mg
IV push: Administer over at least 2 minutes.
Solution for infusion: Administer over 15 to 30 minutes.
Oral: Administer without regard to meals. May administer with antacids.
Suspension: Shake vigorously before use.
Tablet (OTC): To prevent symptoms, administer 10 to 60 minutes before eating food or drinking beverages known to cause heartburn.
Oral: May administer with antacids. May be taken without regard to meals.
Suspension: Shake vigorously for 10 to 15 seconds prior to each use
Tablet (OTC): Do not chew; dose may be taken 10 to 60 minutes before eating food or drinking beverages known to cause heartburn
Parenteral:
IV push: May be administered at a rate of ≤10 mg/minute over at least 2 minutes
IV infusion: Infuse over 15 to 30 minutes
Oral:
Gastroesophageal reflux disease: Treatment of gastroesophageal reflux disease (GERD) and esophagitis due to GERD.
Heartburn (OTC only): Relief of heartburn, acid indigestion, and sour stomach.
Injection:
Patients not able to take oral medication: As an alternative to the oral dosage form for short-term use in patients who are unable to take oral medication.
Aspiration prophylaxis in patients undergoing anesthesia; Chronic spontaneous urticaria; Infusion reaction, premedication; Mastocytosis; Stress ulcer prophylaxis in select critically ill patients
Famotidine may be confused with FLUoxetine, furosemide
Zantac 360 may be confused with Zantac (former brand name for ranitidine)
CNS effects have been reported with famotidine and may include agitation, confusion, and delirium (among others). These effects appear to be reversible with discontinuation (Ref).
Mechanism: Not clearly established; may occur due to increased central anticholinergic action (Ref). There is no evidence to support a difference among agents in the H2-receptor antagonist class (Ref).
Onset: Varied; in case reports, CNS effects occurred within 2 to 6 days of IV famotidine initiation (Ref) and within the first 2 to 3 weeks of oral famotidine use (Ref).
Risk factors :
For H2-receptor antagonists in general:
• Age ≥60 years (Ref)
• Hospitalization, especially ICU (Ref)
• Kidney or liver impairment (Ref)
H2-receptor antagonists, including famotidine, may be associated with an increased incidence of necrotizing enterocolitis in very low birth weight (VLBW) neonates (Ref).
Mechanism: Non–dose-related; possibly due to an increase in gastric pH, which alters the intestinal microbiome and weakens the protective barrier against bacterial overgrowth in the premature gut (Ref).
Risk factors:
• VLBW neonates (<1,500 grams) (Ref)
• Duration of treatment (median duration of exposure: 10 days) (Ref)
• Prematurity (Ref)
Thrombocytopenia has been reported rarely with IV and oral famotidine and may increase the risk of bleeding (Ref). Most patients who developed thrombocytopenia while receiving an H2-receptor antagonist also had at least one documented independent risk factor for thrombocytopenia (eg, age, sepsis) (Ref).
Mechanism: Non–dose-related; postulated to occur secondary to one of two mechanisms: Induction of bone marrow suppression secondary to inhibition of DNA synthesis or development of platelet antibodies during H2-receptor antagonist administration (Ref).
Onset: Varied; in case reports with H2-receptor antagonists, average onset: 14 days (range: 1 to 75 days) (Ref).
Risk factors:
• Higher injury severity scores (Ref)
• Longer length of hospitalization (Ref)
The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified. All reported ADRs are for the oral formulations unless otherwise noted.
>10%: Nervous system: Agitation (infants)
1% to 10%:
Gastrointestinal: Constipation (1%), diarrhea (2%)
Nervous system: Dizziness (1%), headache (5%)
<1%:
Cardiovascular: Flushing, palpitations
Dermatologic: Pruritus, skin rash, xeroderma
Endocrine & metabolic: Decreased libido
Gastrointestinal: Abdominal distress, anorexia, nausea, vomiting, xerostomia
Genitourinary: Impotence
Hematologic & oncologic: Thrombocytopenia
Hepatic: Increased liver enzymes
Nervous system: Anxiety, depression, drowsiness, fatigue, hallucination, insomnia, seizure (von Einsiedel 2002), taste disorder
Neuromuscular & skeletal: Arthralgia, asthenia, musculoskeletal pain
Ophthalmic: Conjunctival injection, periorbital edema
Otic: Tinnitus
Respiratory: Bronchospasm
Miscellaneous: Fever
Frequency not defined: Local: Irritation at injection site (IV)
Postmarketing:
Cardiovascular: Atrioventricular block (Schoenwald 1999), cardiac arrhythmia (Ahmad 1991), facial edema, prolonged QT interval on ECG (Lee 2004)
Dermatologic: Stevens-Johnson syndrome, toxic epidermal necrolysis (Brunner 1995), urticaria
Gastrointestinal: Necrotizing enterocolitis (very low birth weight neonates; Guillet 2006)
Hematologic & oncologic: Agranulocytosis (Marcus 2002), leukopenia, neutropenia (Oymak 1994), pancytopenia
Hepatic: Cholestatic jaundice, hepatitis (Gupta 2009)
Hypersensitivity: Anaphylaxis (Kim 2010), angioedema
Immunologic: Drug reaction with eosinophilia and systemic symptoms (Wu 2012)
Nervous system: Confusion, delirium (Catalano 1996), disorientation (Rodgers 1998; Yoshimoto 1994), mania (von Einsiedel 2002), nightmares (Rodgers 1998), paresthesia, restlessness (Rodgers 1998)
Neuromuscular & skeletal: Muscle cramps, rhabdomyolysis
Renal: Interstitial nephritis (Hirayama 1998)
Respiratory: Interstitial pneumonitis
Serious hypersensitivity (eg, anaphylaxis) to famotidine, other H2 antagonists, or any component of the formulation
OTC labeling: When used for self-medication (OTC), do not use if trouble or pain when swallowing food, vomiting with blood, or bloody or black stools; allergic to other acid reducers; kidney impairment; coadministration with other acid reducers.
Concerns related to adverse effects.
• Vitamin B12 deficiency: Famotidine and other H2RAs can reduce absorption of vitamin B12 and thus decrease serum concentrations. It is unclear of its role in causing function or clinical deficiencies . A number of studies have tried to determine the association of B12 deficiency with H2RAs use; however, differences in diagnostic criteria have made this challenging (Miller 2018).
Disease-related concerns:
• Gastric malignancy: Relief of symptoms does not preclude the presence of a gastric malignancy.
• Kidney impairment: Use with caution; increased risk of QT prolongation; dosage adjustment may be required.
Special populations:
• Older adults: Use with caution.
• Pediatric: Use of gastric acid inhibitors, including proton pump inhibitors and H2 blockers, has been associated with an increased risk for development of acute gastroenteritis and community-acquired pneumonia in pediatric patients (Canani 2006).
Dosage form specific issues:
• Benzyl alcohol and derivatives: Some dosage forms may contain benzyl alcohol and/or sodium benzoate/benzoic acid; benzoic acid (benzoate) is a metabolite of benzyl alcohol; large amounts of benzyl alcohol (≥99 mg/kg/day) have been associated with a potentially fatal toxicity (“gasping syndrome”) in neonates; the “gasping syndrome” consists of metabolic acidosis, respiratory distress, gasping respirations, CNS dysfunction (including convulsions, intracranial hemorrhage), hypotension, and cardiovascular collapse (AAP ["Inactive" 1997]; CDC 1982); some data suggests that benzoate displaces bilirubin from protein binding sites (Ahlfors 2001); avoid or use dosage forms containing benzyl alcohol and/or benzyl alcohol derivative with caution in neonates. See manufacturer’s labeling.
Other warnings/precautions:
• OTC labeling: When used for self-medication (OTC), notify health care provider before use if any of the following are present: Frequent chest pain; frequent wheezing particularly with heartburn; nausea/vomiting; unexplained weight loss; stomach pain; heartburn >3 months; heartburn with light-headedness, sweating, or dizziness; chest pain or shoulder pain with shortness of breath; sweating; pain that spreads to arms, neck, or shoulders; light-headedness. Discontinue use and notify health care provider if heartburn continues or worsens, or if use is required >14 days.
Use of gastric acid inhibitors, including proton pump inhibitors and H2 blockers, has been associated with an increased risk for development of acute gastroenteritis and community-acquired pneumonia in pediatric patients 4 to 36 months of age (Canani 2006). A large epidemiological study has suggested an increased risk for developing pneumonia in patients receiving H2 receptor antagonists; however, a causal relationship with famotidine has not been demonstrated. An approximate sixfold increase in mortality, necrotizing enterocolitis, and infection (ie, sepsis, pneumonia, urinary tract infection) was reported in patients receiving ranitidine in a cohort analysis of 274 very low birth weight neonates (Terrin 2012). Routine use of H2 blockers in preterm infants is not recommended (AAP [Eichenwald 2018]).
Substrate of OAT1/3, OCT1
Note: Interacting drugs may not be individually listed below if they are part of a group interaction (eg, individual drugs within “CYP3A4 Inducers [Strong]” are NOT listed). For a complete list of drug interactions by individual drug name and detailed management recommendations, use the Lexicomp drug interactions program by clicking on the “Launch drug interactions program” link above.
Acalabrutinib: Histamine H2 Receptor Antagonists may decrease the serum concentration of Acalabrutinib. Management: Give acalabrutinib capsules 2 hours before a histamine H2 receptor antagonist (H2RA). No action is required if acalabrutinib tablets are coadministered with H2RAs. Risk D: Consider therapy modification
Atazanavir: Histamine H2 Receptor Antagonists may decrease the serum concentration of Atazanavir. Management: Specific dose limitations and administration guidelines exist; consult full interaction monograph or atazanavir prescribing information. Risk D: Consider therapy modification
Belumosudil: Histamine H2 Receptor Antagonists may decrease the serum concentration of Belumosudil. Risk C: Monitor therapy
Bosutinib: Histamine H2 Receptor Antagonists may decrease the serum concentration of Bosutinib. Management: Administer histamine H2 receptor antagonists more than 2 hours before or after bosutinib. Risk D: Consider therapy modification
Cefditoren: Histamine H2 Receptor Antagonists may decrease the serum concentration of Cefditoren. Risk X: Avoid combination
Cefpodoxime: Histamine H2 Receptor Antagonists may decrease the serum concentration of Cefpodoxime. Risk C: Monitor therapy
Cefuroxime: Histamine H2 Receptor Antagonists may decrease the absorption of Cefuroxime. Separate oral doses by at least 2 hours. Risk X: Avoid combination
Cysteamine (Systemic): Histamine H2 Receptor Antagonists may diminish the therapeutic effect of Cysteamine (Systemic). Risk C: Monitor therapy
Dacomitinib: Histamine H2 Receptor Antagonists may decrease the serum concentration of Dacomitinib. Management: Administer dacomitinib at least 6 hours before or 10 hours after an histamine H2-receptor antagonist (H2RA). Risk D: Consider therapy modification
Dasatinib: Histamine H2 Receptor Antagonists may decrease the absorption of Dasatinib. Management: Antacids (taken 2 hours before or after dasatinib administration) can be used in place of H2-antagonists if some acid-reducing therapy is needed. Risk X: Avoid combination
Delavirdine: Histamine H2 Receptor Antagonists may decrease the serum concentration of Delavirdine. Risk X: Avoid combination
Dichlorphenamide: May increase the serum concentration of Famotidine. Risk X: Avoid combination
Enoxacin: Histamine H2 Receptor Antagonists may decrease the absorption of Enoxacin. Risk C: Monitor therapy
Erlotinib: Histamine H2 Receptor Antagonists may decrease the serum concentration of Erlotinib. Management: Avoid H2-antagonists in patients receiving erlotinib when possible. If concomitant treatment cannot be avoided, erlotinib should be dosed once daily, 10 hours after and at least 2 hours before H2-antagonist dosing. Risk D: Consider therapy modification
Fosamprenavir: Histamine H2 Receptor Antagonists may decrease the serum concentration of Fosamprenavir. Cimetidine may also inhibit the metabolism of the active metabolite amprenavir, making its effects on fosamprenavir/amprenavir concentrations difficult to predict. Risk C: Monitor therapy
Gefitinib: Histamine H2 Receptor Antagonists may decrease the serum concentration of Gefitinib. Management: Administer gefitinib at least 6 hours before or 6 hours after administration of a histamine H2 receptor antagonist (H2RA), and closely monitor clinical response to gefitinib. Risk D: Consider therapy modification
Indinavir: Histamine H2 Receptor Antagonists may decrease the serum concentration of Indinavir. Risk C: Monitor therapy
Infigratinib: Histamine H2 Receptor Antagonists may decrease serum concentrations of the active metabolite(s) of Infigratinib. Histamine H2 Receptor Antagonists may decrease the serum concentration of Infigratinib. Management: Avoid coadministration of infigratinib with histamine receptor antagonists (H2RAs) or other gastric acid-lowering agents. If H2RAs cannot be avoided, administer infigratinib 2 hours before or 10 hours after administration of H2RAs. Risk D: Consider therapy modification
Itraconazole: Histamine H2 Receptor Antagonists may increase the serum concentration of Itraconazole. Histamine H2 Receptor Antagonists may decrease the serum concentration of Itraconazole. Management: Administer Sporanox brand itraconazole at least 2 hours before or 2 hours after administration of any histamine H2 receptor antagonists (H2RAs). Exposure to Tolsura brand itraconazole may be increased by H2RAs; consider itraconazole dose reduction. Risk D: Consider therapy modification
Ketoconazole (Systemic): Histamine H2 Receptor Antagonists may decrease the serum concentration of Ketoconazole (Systemic). Management: Administer ketoconazole with an acidic beverage (eg, non-diet cola) and monitor for reduced efficacy if concomitant use with a H2RA is required. Increases in ketoconazole dose may be required. Risk D: Consider therapy modification
Ledipasvir: Histamine H2 Receptor Antagonists may decrease the serum concentration of Ledipasvir. Management: Administer H2 receptor antagonist doses less than or comparable to famotidine 40 mg twice daily simultaneously or 12 hours prior to ledipasvir. The effect of administering H2 receptor antagonists at other time intervals is unknown and not recommended. Risk D: Consider therapy modification
Levoketoconazole: Histamine H2 Receptor Antagonists may decrease the absorption of Levoketoconazole. Risk X: Avoid combination
Multivitamins/Minerals (with ADEK, Folate, Iron): Histamine H2 Receptor Antagonists may decrease the serum concentration of Multivitamins/Minerals (with ADEK, Folate, Iron). Specifically, the absorption of iron may be impaired by H2-antagonists. Risk C: Monitor therapy
Nelfinavir: Histamine H2 Receptor Antagonists may decrease serum concentrations of the active metabolite(s) of Nelfinavir. Histamine H2 Receptor Antagonists may decrease the serum concentration of Nelfinavir. Concentrations of the active M8 metabolite may also be reduced. Risk C: Monitor therapy
Neratinib: Histamine H2 Receptor Antagonists may decrease the serum concentration of Neratinib. Specifically, histamine H2 receptor antagonists may reduce neratinib absorption. Management: Administer neratinib at least 2 hours before or 10 hours after administration of a histamine H2 receptor antagonist to minimize the impact of this interaction. Risk D: Consider therapy modification
Nilotinib: Histamine H2 Receptor Antagonists may decrease the serum concentration of Nilotinib. Management: The nilotinib dose should be given 10 hours after or 2 hours before the H2 receptor antagonist in order to minimize the risk of a significant interaction. Risk D: Consider therapy modification
Octreotide: Histamine H2 Receptor Antagonists may decrease the serum concentration of Octreotide. Risk C: Monitor therapy
PAZOPanib: Histamine H2 Receptor Antagonists may decrease the serum concentration of PAZOPanib. Risk X: Avoid combination
Pexidartinib: Histamine H2 Receptor Antagonists may decrease the serum concentration of Pexidartinib. Management: Administer pexidartinib 2 hours before or 10 hours after histamine H2 receptor antagonists. Risk D: Consider therapy modification
Posaconazole: Histamine H2 Receptor Antagonists may decrease the serum concentration of Posaconazole. Management: Avoid concurrent use of oral suspension with H2-antagonists whenever possible. Monitor patients closely for decreased antifungal effects if this combination is used. Delayed-release posaconazole tablets may be less likely to interact. Risk D: Consider therapy modification
Rilpivirine: Histamine H2 Receptor Antagonists may decrease the serum concentration of Rilpivirine. Management: Administer histamine H2 receptor antagonists (H2RAs) at least 12 hours before or 4 hours after oral rilpivirine. Risk D: Consider therapy modification
Risedronate: Histamine H2 Receptor Antagonists may increase the serum concentration of Risedronate. This applies specifically to delayed-release risedronate. Risk X: Avoid combination
Saquinavir: Histamine H2 Receptor Antagonists may increase the serum concentration of Saquinavir. Management: Consider alternatives to this combination for patients taking the Invirase formulation of saquinavir. No action beyond standard clinical care measures is required for patients taking the Fortovase formulation of saquinavir. Risk D: Consider therapy modification
Secretin: Histamine H2 Receptor Antagonists may diminish the diagnostic effect of Secretin. Specifically, use of H2-Antagonists may cause a hyperresponse in gastrin secretion in response to secretin stimulation testing, falsely suggesting gastrinoma. Management: Avoid concomitant use of histamine H2-antagonists (H2RAs) and secretin. Discontinue H2RAs at least 2 days prior to secretin administration. Risk D: Consider therapy modification
Selpercatinib: Histamine H2 Receptor Antagonists may decrease the serum concentration of Selpercatinib. Management: Coadministration of selpercatinib and H2 receptor antagonists should be avoided. If coadministration cannot be avoided, selpercatinib should be administered 2 hours before or 10 hours after H2 receptor antagonists. Risk D: Consider therapy modification
Sotorasib: Histamine H2 Receptor Antagonists may decrease the serum concentration of Sotorasib. Risk X: Avoid combination
Sparsentan: Histamine H2 Receptor Antagonists may decrease the serum concentration of Sparsentan. Risk X: Avoid combination
Velpatasvir: Histamine H2 Receptor Antagonists may decrease the serum concentration of Velpatasvir. Risk C: Monitor therapy
Prolonged treatment (≥2 years) may lead to malabsorption of dietary vitamin B12 and subsequent vitamin B12 deficiency (Lam 2013).
Famotidine crosses the placenta (Wang 2013).
Due to pregnancy-induced physiologic changes, renal clearance of famotidine may be increased (Wang 2011).
Histamine H2 antagonists have been evaluated for the treatment of gastroesophageal reflux disease (GERD) during pregnancy. Agents other than famotidine may be preferred for initial therapy (Richter 2005; van der Woude 2014). Histamine H2 antagonists may be used for aspiration prophylaxis prior to cesarean delivery (ASA 2016).
Famotidine is present in breast milk.
The relative infant dose (RID) of famotidine is 2.2% when calculated using the highest breast milk concentration located and compared to an infant therapeutic dose of 0.5 mg/kg/day.
In general, breastfeeding is considered acceptable when the RID of a medication is <10% (Anderson 2016; Ito 2000).
The RID of famotidine was calculated using a milk concentration of 0.072 mcg/mL, providing an estimated daily infant dose via breast milk of 0.011 mg/kg/day. This milk concentration was obtained following maternal administration of a single dose of famotidine 40 mg orally (Courtney 1988).
According to the manufacturer, the decision to breastfeed during therapy should consider the risk of infant exposure, the benefits of breastfeeding to the infant, and benefits of treatment to the mother. When treatment with a histamine H2 antagonist is needed, famotidine is one of the preferred agents due to its lower concentrations in breast milk (Richter 2005).
CBC, gastric pH, occult blood with GI bleeding
Competitive inhibition of histamine at H2 receptors of the gastric parietal cells, which inhibits gastric acid secretion
Onset of action: Antisecretory effect: Oral: Within 1 hour
Peak effect: Antisecretory effect: Oral: Within 1 to 3 hours (dose-dependent); IV: Within 30 minutes
Duration: Antisecretory effect: IV, Oral: 10 to 12 hours
Absorption: Oral: Incompletely absorbed
Distribution: Vd: IV:
Infants: ≤3 months: 1.4 ± 0.4 L/kg to 1.8 ± 0.3 L/kg; >3 to 12 months: 2.3 ± 0.7 L/kg
Children <11 years: 2.07 ± 1.49 L/kg
Children ≥11 years and Adolescents ≤15 years: 1.5 ± 0.4 L/kg
Adults: 1.3 ± 0.2 L/kg
Protein binding: 15% to 20%
Metabolism: 30% to 35%; minimal first-pass metabolism; forms one metabolite (S-oxide)
Bioavailability: Oral: 40% to 45%
Half-life elimination: IV:
Infants: ≤3 months: 8.1 ± 3.5 hours to 10.5 ± 5.4 hours; >3 to 12 months: 4.5 ± 1.1 hours
Children <11 years: 3.38 ± 2.6 hours
Children ≥11 years and Adolescents ≤15 years: 2.3 ± 0.4 hours
Adults: 2.5 to 3.5 hours; prolonged with kidney impairment; Oliguria: >20 hours; Anuria: 24 hours
Time to peak, serum: Oral: ~1 to 3 hours
Excretion: Urine (25% to 30% [oral], 65% to 70% [IV] as unchanged drug)
Clearance: IV:
Infants: ≤3 months: 0.13 ± 0.06 to 0.21 ± 0.06 L/hour/kg; >3 to 12 months: 0.49 ± 0.17 L/hour/kg
Children <11 years: 0.54 ± 0.34 L/hour/kg
Children ≥11 years and Adolescents ≤15 years: 0.48 ± 0.14 L/hour/kg
Adults: 0.39 ± 0.14 L/hour/kg
Altered kidney function: AUC increased at least 5-fold and at least 2-fold in adults with CrCl <30 mL/minute and CrCl 30 to 60 mL/minute, respectively.
Solution (Famotidine (PF) Intravenous)
20 mg/2 mL (per mL): $0.44 - $0.57
Solution (Famotidine Intravenous)
40 mg/4 mL (per mL): $0.53 - $0.75
200 mg/20 mL (per mL): $0.41 - $0.54
Suspension (reconstituted) (Famotidine Oral)
40 mg/5 mL (per mL): $3.54
Tablets (Famotidine Oral)
10 mg (per each): $0.08 - $0.26
20 mg (per each): $0.06 - $2.43
40 mg (per each): $0.08 - $4.86
Tablets (Pepcid Oral)
20 mg (per each): $15.87
40 mg (per each): $30.67
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