Pepcid AC: Uses, Side Effects & Dosage | Healio

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Pepcid AC

Brand Names

Pepcid AC, Zantac-360

Generic Name

famotidine

Phonetic Name

(fa-MOE-ti-deen)

Clinical Uses

Famotidine is known as an H2 blocker. It works by reducing the amount of acid in your stomach. It is used to prevent and treat heartburn and other symptoms caused by too much acid in the stomach (acid indigestion). Check the ingredients on the label even if you have used the product before. The manufacturer may have changed the ingredients. Also, products with similar names may contain different ingredients meant for different purposes. Taking the wrong product could harm you.

Dosage and Administration

Preparations

40 mg/5 mL Brand(s): Pepcid(R), Merck Tablets
10 mg Brand(s): Pepcid(R) AC Gelcaps, J&J-Merck Tablets
10 mg Brand(s): Pepcid(R) AC, J&J-Merck chewable Tablets
10 mg Brand(s): Pepcid(R) AC, J&J-Merck film-coated
20 mg Brand(s): * Pepcid(R), Merck Pepcid(R) AC Maximum Strength, J&J-Merck
40 mg Brand(s): Pepcid(R), Merck Tablets
20 mg Brand(s): Pepcid(R) RPD, Merck orally disintegrating
40 mg Brand(s): Pepcid(R) RPD, Merck

10 mg Brand(s): /mL Famotidine for Injection Merck concentrate (pharmacy bulk package) For injection
10 mg Brand(s): /mL Famotidine for Injection Merck concentrate, for IV use Pepcid(R) I.V., Merck

Administration Notes

To treat heartburn and acid indigestion, take 1 tablet or capsule with a glass of water as needed, unless otherwise directed by your doctor. Swallow the tablets and capsules whole without chewing. If you are using the chewable tablets, chew completely and swallow one tablet as needed. Do not swallow whole. Famotidine can be taken with or without food. To prevent heartburn and acid indigestion, take famotidine 15-60 minutes before eating food or drinking beverages that can cause indigestion. Do not take more than 2 tablets in 24 hours unless directed by your doctor. Follow all directions on the product package. If you have any questions, ask your doctor or pharmacist. Tell your doctor if your symptoms last or if they get worse. Do not take this medicine for more than 14 days in a row without talking with your doctor.

Missed Dose Instructions

Not applicable.

Indications

dyspepsia
gastroesophageal reflux disease
heartburn

heartburn prevention

duodenal ulcer
dyspepsia prevention
gastric ulcer
maintenance of healing duodenal ulcer
prevention of stress ulcer

Contraindications

chronic kidney disease stage 3A (moderate) GFR 45-59 mL/min
chronic kidney disease stage 3B (moderate) GFR 30-44 mL/min
chronic kidney disease stage 4 (severe) GFR 15-29 mL/min
chronic kidney disease stage 5 (failure) GFR<15 mL/min
gastric cancer

kidney disease with likely reduction in glomerular filtration rate (GFR)

Common Adverse Effects

Constipation
Diarrhea
Dizziness
Headache disorder

Musculoskeletal pain

Acne vulgaris
Acute abdominal pain
Acute cognitive impairment
Agitation
Allergic conjunctivitis
Alopecia
Anorexia
Anticholinergic toxicity
Arthralgia
Cramps
Delirium
Drowsy
Dry skin
Dysgeusia
Facial edema
Fatigue
Fever
Flushing
General weakness
Hallucinations
Insomnia
Lethargy
Nausea
Paresthesia
Pruritus of skin
Tinnitus
Vomiting
Xerostomia

Serious Adverse Effects

Abnormal hepatic function tests
Agranulocytosis
Anaphylaxis
Anemia
Angioedema
Atrioventricular block
Bronchospastic pulmonary disease
Cardiac arrhythmia
Dyspnea
Hepatitis
Hypotension
Increased alanine transaminase
Increased aspartate transaminase
Interstitial pneumonitis
Leukopenia
Obstructive hyperbilirubinemia
Pancytopenia
Psychiatric disorder
Rhabdomyolysis
Seizure disorder
Skin rash
Stevens-Johnson syndrome
Thrombocytopenic disorder
Toxic epidermal necrolysis
Urticaria

Elderly Precautions

SeverityNarrativeManagement or Monitoring PrecautionNeuro/Psych-Avoid in older adults with or at high risk of delirium because of inducing or worsening delirium. Avoid in elderly with dementia or cognitive impairment. Renal-Dose adjustment may be required for CrCL<50 mL/min. to minimize CNS effects (e.g., mental status changes).

Pregnancy Precautions

PrecautionSeverityNarrativeFAMOTIDINERequires a Risk/Benefit AssessmentAvailable human data have not identified an increased risk of developmental toxicity. Consider maternal treatment benefits versus potential fetal/neonatal adverse outcomes. Animal data suggest no developmental toxicity.

Lactation Precautions

SeverityNarrativePrecautionLIMITED DATA SUGGEST LOW AMOUNTS EXCRETED, WITH NO RESULTING EFFECT ON INFANT

Pediatric Precautions

Drug Interactions

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval. A product that may interact with this drug is: fezolinetant. Some products need stomach acid so that the body can absorb them properly. Famotidine decreases stomach acid, so it may change how well these products work. Some affected products include atazanavir, dasatinib, certain azole antifungals (such as itraconazole, ketoconazole), levoketoconazole, pazopanib, sparsentan, among others. Do not take this medication with other products that contain famotidine or other H2 blockers (cimetidine, nizatidine, ranitidine).

Drug Interactions Table

Toxicology

There has been no experience to date with acute overdosage of famotidine.

No evidence of mutagenicity was observed in in vitro studies using famotidine concentrations up to 10 mg per plate in the Ames microbial mutagen test with or without metabolic activation and in in vivo studies in mice using a micronucleus test and a chromosomal aberration test. No evidence of carcinogenicity was seen in long-term studies in mice or rats receiving oral famotidine dosages up to 2 g/kg daily (approximately 2500 times the usual human dosage). Although famotidine did not produce changes in gastric mucosal cells in animals, long-term effects of the drug on human gastric mucosal morphology are not known, and the risk, if any, of gastric neoplasms and long-term therapy with an H2-receptor antagonist remains controversial.

Chemical Properties

Famotidine is a histamine H2-receptor antagonist. Unlike the earlier histamine H2-receptor antagonists, burimamide and metiamide, which are not commercially available, and cimetidine and ranitidine, famotidine contains a guanidine-substituted thiazole ring rather than an imidazole or furan ring. Famotidine occurs as a white to pale yellow, odorless, crystalline powder having a moderately bitter taste. Famotidine has solubilities of 740 mcg/mL in water and 360 mcg/mL in alcohol at 20degreesC. The drug has a pKa of 7.1 in water at 25degreesC. Famotidine is commercially available for oral administration as film-coated, chewable, gelatin-coated, or orally disintegrating tablets and as a powder for oral suspension. Some famotidine chewable tablet preparations (Pepcid(R) AC) and famotidine orally disintegrating tablets (Pepcid RPD(R)) contain aspartame (Nutrasweet(R)). Following metabolism of aspartame in the GI tract, each 20- or 40-mg orally disintegrating tablet provides 1.05 or 2.1 mg, respectively, of phenylalanine. Famotidine powder for suspension occurs as a white to off-white powder. When reconstituted as directed, oral suspensions of the drug occur as smooth, mobile, off-white homogenous suspensions and have a pH of 6.5-7.5. Famotidine concentrate for injection is a clear, colorless, sterile solution of the drug in water for injection. The concentrate also contains mannitol; multiple-dose vials also contain benzyl alcohol as a preservative. Famotidine concentrate for injection has a pH of 5-5.6. The preservative-free injection has an osmolarity of 217 mOsm/L, and the injection preserved with benzyl alcohol has an osmolarity of 290 mOsm/L. Famotidine injection that is commercially available as a diluted solution in 0.9% sodium chloride is iso-osmotic and has a pH of 5.7-6.4. This injection contains approximately 7.8 mEq of sodium per 50 mL.

Pharmacokinetics

Absorption: Famotidine is incompletely absorbed from the GI tract following oral administration, and the drug reportedly undergoes minimal first-pass metabolism. The oral bioavailability of famotidine in adults is about 40-50%. Studies in a limited number of children 11-15 years of age indicate a similar oral bioavailability of famotidine (mean bioavailability: 50%). The film-coated tablets, oral suspension, and orally disintegrating tablets of famotidine reportedly are bioequivalent. Food may slightly enhance and antacids may slightly decrease the bioavailability of famotidine, but these alterations do not appear to be clinically important. Following IV injection of a single 20-mg dose of famotidine, peak plasma concentrations of 272 ng/mL occur within 20 minutes and decrease to 163, 98, 64, 25, and 11 ng/mL 1, 2, 4, 8, and 12 hours, respectively, after the dose. Following oral administration of a 5-, 10-, 20-, or 40-mg dose of famotidine, peak plasma concentrations of 17-22, 29-39, 40-71, or 78-132 ng/mL, respectively, occur within 1-4 hours. Plasma famotidine concentrations necessary to inhibit 50% of tetragastrin-stimulated gastric acid secretion (IC50) are estimated to be 13 ng/mL. Plasma famotidine concentrations greater than 50 ng/mL result in inhibition of more than 80% of gastric acid secretion; however, inhibition generally appears to diminish at lower concentrations. Data are conflicting regarding the relationship between plasma famotidine concentrations and a given therapeutic effect of acid inhibition. However, in one study, the decline in the degree of inhibition of gastric acid secretion appeared to be proportional to decreases in plasma famotidine concentrations. Inhibition of gastric acid secretion is apparent within 1 hour following IV or oral administration of famotidine. Peak inhibition occurs within 0.5-3 or 1-4 hours following IV or oral administration, respectively. The duration of inhibition of gastric acid secretion and maximal inhibition produced by famotidine are dose dependent. The duration of inhibition of basal and nocturnal secretion following a single 20- or 40-mg oral dose of the drug reportedly is 10-12 hours. Inhibition of food-stimulated secretion generally persists for 8-10 hours when these doses are administered in the morning, but this inhibition may dissipate within 6-8 hours after a 20-mg oral dose in some patients. Following equipotent doses of famotidine (60 mg), cimetidine (1.9 g), or ranitidine (530 mg) in one study in patients with GI hypersecretory conditions, gastric acid secretion 12 hours after discontinuance of the drugs was reduced by 58, 27, or 38%, respectively, compared with basal secretion, and the time required for secretion to return to 20 mEq/hour averaged 12, 9, or 10 hours, respectively, following discontinuance of the drugs. The duration of inhibition of nocturnal gastric acid secretion is 10-15 hours following a single 10- or 20-mg IV famotidine dose. In one study in healthy individuals who were hypersecretors of gastric acid (basal gastric acid output of 5 or more mEq/hour), maximal inhibition of gastric acid secretion was 97.4, 99.7, or 99.4% 2-4 hours and 73.8, 77.2, or 83.3% 12 hours following a single famotidine dose of 10 or 20 mg IV or 20 mg orally, respectively. Distribution: Distribution of famotidine into human body tissues and fluids has not been fully characterized. The apparent volume of distribution of the drug is reported to be 1.1-1.4 L/kg in adults and does not appear to be altered substantially in patients with renal dysfunction. In children 1-15 years of age, a volume of distribution of 1.5-2.07 L/kg has been reported. Following oral or IV administration in rats, famotidine is widely distributed, appearing in highest concentrations in the kidney, liver, pancreas, and submandibular gland. The drug is 15-20% protein bound. In rats, famotidine appears to distribute only minimally into the CNS, and does not cross the placenta. It is not known whether the drug crosses the placenta in humans. Famotidine is distributed into milk in rats; however, it is not known whether the drug is distributed into milk in humans. Elimination: The elimination half-life of famotidine averages 2.5-4 hours in adults with normal renal function. An elimination half-life of 2.3-3.38 hours has been reported in children 1-15 years of age. The elimination of famotidine does not appear to be affected substantially by age in adults, but is prolonged in patients with renal impairment; adjustment of dosage or dosing interval may be necessary to avoid excess accumulation of the drug in patients with moderate or severe renal impairment. In adults with creatinine clearances of 10 mL or less per minute, the elimination half-life of the drug may exceed 20 hours, with an elimination half-life of about 24 hours in anuric patients. There is some evidence that plasma concentrations of famotidine decline in a biphasic manner. In adults with normal renal function and those with creatinine clearances of 60-90, 30-60, or less than 30 mL/minute per 1.48 m2, the plasma half-life in the distribution phase (t1/2alpha) was not affected substantially by renal function, averaging 0.18, 0.23, 0.25, or 0.24 hours, respectively; the half-life in the terminal elimination phase (t1/2beta) averaged 2.6, 2.9, 4.7, or 12 hours, respectively. Famotidine is metabolized in the liver to famotidine S-oxide (S-famotidine). The metabolite does not appear to inhibit gastric acid secretion. Orally administered famotidine undergoes minimal metabolism on first pass through the liver. Famotidine is excreted principally in urine via glomerular filtration and tubular secretion. Approximately 25-30 or 65-80% of a dose is excreted unchanged in urine within 24 hours following oral or IV administration, respectively, and approximately 13-49 or 52-82% of a single 40-mg oral or IV dose, respectively, is excreted within 72 hours. The cumulative renal excretion of famotidine is decreased in patients with renal dysfunction, with 72, 69, 65, or 21% of an administered dose excreted in individuals with normal renal function or those with creatinine clearances of 60-90, 30-60, or less than 30 mL/minute per 1.48 m2, respectively. A small fraction of an orally administered dose is excreted in urine as famotidine S-oxide. The remainder of an orally administered dose is eliminated in feces. Nonrenal excretion of famotidine did not show a compensatory increase in patients with severe renal impairment, but rather decreased by about 40% in these patients. Interindividual variation in the metabolism and excretion of famotidine has been reported. Following oral administration of a 20-mg dose, 24-56 or 28-79% of the administered dose reportedly was excreted in urine or feces, respectively. Total body clearance of famotidine from plasma averages 381-483 mL/minute, and renal clearance of the drug averages 250-450 mL/minute. Total body and renal clearances are decreased in patients with renal dysfunction. In patients with creatinine clearances of 30-60 or less than 30 mL/minute per 1.48 m2, total body clearance from plasma averaged 241 or 71-83 mL/minute, respectively, and renal clearance averaged 157 or 9.5-21 mL/minute, respectively. Famotidine does not appear to be removed by hemodialysis.

Stability Information

Commercially available famotidine film-coated tablets (Pepcid(R)) should be stored in well-closed, light-resistant containers at 25degreesC, but may be exposed to temperatures ranging from 15-30degreesC. These tablets have an expiration date of 30 months following the date of manufacture when stored under these conditions. Famotidine orally disintegrating tablets (Pepcid RPD(R)) should be stored at 25degreesC, but may be exposed to temperatures ranging from 15-30degreesC. Famotidine tablets and chewable tablets for self-medication (Pepcid(R) AC, Pepcid(R) Complete) should be stored at a temperature between 25-30degreesC and protected from moisture. Commercially available famotidine powder for oral suspension should be stored in tight containers at 25degreesC, but may be exposed to temperatures ranging from 15-30degreesC. The powder for oral suspension has an expiration date of 18 months following the date of manufacture when stored at a temperature less than 40degreesC. Following reconstitution, oral suspensions of the drug should be stored at a temperature less than 30degreesC and, although not necessary, may be refrigerated; freezing should be avoided. Any unused suspension should be discarded after 30 days. Commercially available famotidine concentrate for injection should be refrigerated at 2-8degreesC and has an expiration date of 24 months following the date of manufacture when stored at this temperature. If freezing occurs, the injection should be thawed at room temperature or by warming it in a water bath or under running hot tap water, allowing sufficient time for dissolution of all ingredients. The injection should not be thawed by exposure to microwave radiation because of the potential hazard of rapidly increased temperature and vapor pressure in a closed system. When diluted with most commonly used IV solutions (e.g., 0.9% sodium chloride injection, 5 or 10% dextrose injection, lactated Ringer's, water for injection), famotidine solutions are stable for 7 days at room temperature. However, the manufacturer states that data on the maintenance of sterility of these solutions after dilution are unavailable. Therefore, the manufacturer recommends that solutions prepared by dilution of famotidine concentrate for injection, if not used immediately after dilution, should be refrigerated and used within 48 hours. Famotidine injection that is commercially available as a diluted solution in 0.9% sodium chloride should be stored at room temperature (25degreesC) and is stable for 15 months when stored as recommended. Brief exposure to temperatures up to 35degreesC will not adversely affect the stability of the solution, but the solution should be protected from exposure to excessive heat. The commercially available injection of famotidine in 0.9% sodium chloride is provided in a plastic container fabricated from specially designed multilayered plastic PL 2501 (Galaxy(R) container). Solutions in contact with the plastic can leach out some of its chemical components in very small amounts within the expiration period of the injection; however, safety of the plastic has been confirmed in tests in animals according to USP biological tests for plastic containers as well as by tissue culture toxicity studies. The American Society of Health-System Pharmacists, Inc. represents that the information provided in the accompanying monograph was formulated with a reasonable standard of care, and in conformity with professional standards in the field. Readers are advised that decisions regarding use of drugs are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and that the information contained in the monograph is provided for informational purposes only. The manufacturer's labeling should be consulted for more detailed information. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information contained in the monograph is not a substitute for medical care.

Storage Requirements

Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets. Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.

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