famotidine

REMS

Short-term treatment of active duodenal ulcers and benign gastric ulcers.
Maintenance therapy for duodenal ulcers after healing of active ulcer(s).
Gastroesophageal reflux disease (GERD).
Heartburn, acid indigestion, and sour stomach (OTC use).
Gastric hypersecretory states (Zollinger-Ellison syndrome).
Prevention and treatment of stress-induced upper GI bleeding in critically ill patients.

Unlabeled Use:

GI symptoms associated with the use of NSAIDs.
Prevention of stress ulceration or aspiration pneumonitis.
Management of urticaria.

Action ⬆ ⬇

Inhibits the action of histamine at the H₂-receptor site located primarily in gastric parietal cells, resulting in inhibition of gastric acid secretion.

Therapeutic effects:

Healing and prevention of ulcers.
Decreased symptoms of GERD.
Decreased secretion of gastric acid.

Pharmacokinetics ⬆ ⬇

Absorption: 40–45% absorbed following oral administration.

Distribution: Enters cerebrospinal fluid.

Metabolism/Excretion: Up to 70% excreted unchanged by the kidneys, 30–35% metabolized by the liver.

Half-Life: Infants: 4.5–15 hr; Children: 3.3–5.7 hr; Adults: 2.5–3.5 hr.

Time/Action Profile ⬆ ⬇

ROUTE	ONSET	PEAK	DURATION
PO	within 60 min	1–4 hr	6–12 hr
IV	within 60 min	0.5–3 hr	8–15 hr

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity;
Phenylketonuria (chewable tablets only).

Use Cautiously in:

Renal impairment (more susceptible to adverse CNS reactions; ↑ dosage interval recommended if CCr <10 mL/min);
OB: Use during pregnancy only if potential maternal benefit outweighs potential fetal risk;
Lactation: Use while breastfeeding only if potential maternal benefit outweighs potential risk to infant;
Pedi: Injection contains benzyl alcohol, which has been associated with gasping syndrome in neonates;
Geri: Older adults are more susceptible to adverse CNS reactions; dose recommended.

Adv. Reactions/Side Effects ⬆ ⬇

CV: ARRHYTHMIAS

Endo: gynecomastia

GI: constipation, diarrhea, nausea

GU: ↓sperm count, erectile dysfunction

Hemat: AGRANULOCYTOSIS, APLASTIC ANEMIA, anemia, neutropenia, thrombocytopenia

Neuro: confusion, dizziness, drowsiness, hallucinations, headache

Interactions ⬆ ⬇

Drug-drug:

May ↓ absorption of ketoconazole, itraconazole, atazanavir, and gefitinib.

Route/Dosage ⬆ ⬇

PO (Adults ): Short-term treatment of active ulcers: 40 mg/day at bedtime or 20 mg twice daily for up to 8 wk.Duodenal ulcer prophylaxis: 20 mg once daily at bedtime. GERD: 20 mg twice daily for up to 6 wk; up to 40 mg twice daily for up to 12 wk for esophagitis with erosions, ulcerations, and continuing symptoms. Gastric hypersecretory conditions: 20 mg every 6 hr initially, up to 160 mg every 6 hr. OTC use: 10 mg for relief of symptoms; for prevention—10 mg 60 min before eating or take 10 mg as chewable tablet 15 minutes before heartburn-inducing foods or beverages (not to exceed 20 mg/24 hr for up to 2 wk).
PO IV (Children 1–12 yr): Peptic ulcer: 0.5 mg/kg/day as a single bedtime dose or in divided doses twice daily (maximum: 40 mg daily); GERD: 1 mg/kg/day in divided doses twice daily (maximum: 80 mg daily).
PO (Infants > 3 mo—1 yr): GERD: 0.5 mg/kg/dose twice daily.
PO (Infants and neonates <3 mo): GERD: 0.5 mg/kg/dose once daily.
IV (Adults ): 20 mg every 12 hr.

Renal Impairment

PO (Adults ): CCr 10–50 mL/min:administer normal dose every 24 hr or 50% dose at normal dosing intervalCCr <10 mL/min: 20 mg at bedtime; interval may need to be ↑ to every 36–48 hr.

Availability ⬆ ⬇

(Generic available)

Tablets: 10 mg^OTC; 20 mg^{Rx, OTC}; 40 mg
Oral suspensioncherry-banana-mint flavor: 40 mg/5 mL
Premixed infusion: 20 mg/50 mL 0.9% NaCl
Solution for injection: 10 mg/mL
In combination with: calcium carbonate/magnesium hydroxide (Pepcid Complete). See Appendix [not included in this PDA edition].

Assessment ⬆ ⬇

Assess for epigastric or abdominal pain and frank or occult blood in the stool, emesis, or gastric aspirate.
Geri: Assess elderly and debilitated patients routinely for new onset of confusion. Report promptly.

Lab Test Considerations:

Monitor CBC with differential periodically during therapy.
- Antagonize effects of pentagastrin and histamine during gastric acid secretion testing. Avoid administration for 24 hr preceding the test.
- May cause false-negative results in skin tests using allergenic extracts. Histamine antagonists should be discontinued 24 hr prior to the test.
- May cause an ↑ in serum transaminases and serum creatinine.
- May cause false-positive results for urine protein; test with sulfosalicylic acid.

Implementation ⬆ ⬇

PO: Administer with meals or immediately afterward and at bedtime to prolong effect.
- Administer once daily doses at bedtime to prolong effect.
- Shake oral suspension prior to administration. Discard unused suspension after 30 days.

IV Administration:

Diluent: 0.9% NaCl for injection.Concentration: not >4 mg/mL.
Rate: Administer at a rate of 10 mg/min over at least 2 min. Rapid administration may cause hypotension.
Intermittent Infusion: Diluent: Dilute each 20 mg in 100 mL of 0.9% NaCl, D5W, D10W, or LR solution.Concentration: 0.2 mg/mL. Diluted solution is stable for 48 hr at room temperature. Do not use solution that is discolored or contains a precipitate.
Rate: Administer over 15–30 min.

Patient/Family Teaching ⬆ ⬇

Instruct patient to take famotidine as directed for the full course of therapy, even if feeling better. Take missed doses as soon as remembered but not if almost time for next dose. Do not double doses.
- Advise patients taking OTC preparations not to take the maximum dose continuously for more than 2 wk without consulting health care professional. Notify health care professional if difficulty swallowing occurs or abdominal pain persists.
- Inform patient that smoking interferes with the action of histamine antagonists. Encourage patient to quit smoking or at least not to smoke after last dose of the day.
- May cause drowsiness or dizziness. Caution patient to avoid driving or other activities requiring alertness until response to the drug is known.
- Advise patient to avoid alcohol, products containing aspirin or NSAIDs, and foods that may cause an increase in GI irritation.
- Inform patient that increased fluid and fiber intake and exercise may minimize constipation.
- Advise patient to report onset of black, tarry stools; fever; sore throat; diarrhea; dizziness; rash; confusion; or hallucinations to health care professional promptly.
- Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected or if breastfeeding.

Evaluation/Desired Outcomes ⬆ ⬇

Decrease in abdominal pain, heartburn, acid indigestion, and sour stomach.
Prevention of gastric irritation and bleeding. Healing of duodenal ulcers can be seen by endoscopy. Therapy is continued for at least 6 wk in treatment of ulcers but not usually longer than 8 wk.
Decreased symptoms of GERD.

section name header

Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇