Famotidine; Uses, Dosage, Side effects, Drug Interactions

Famotidine is a histamine H₂ receptor antagonist that inhibits stomach acid production. It is a competitive histamine H2-receptor antagonist. Its main pharmacodynamic effect is the inhibition of gastric secretion. It is commonly used in the treatment of peptic ulcer disease and gastroesophageal reflux disease. Unlike cimetidine, the first H₂ antagonist, famotidine has no effect on the cytochrome P450 enzyme system and does not appear to interact with other drugs.

Mechanism of Action of Famotidine

Famotidine binds competitively to H₂-receptors located on the basolateral membrane of the parietal cell, blocking histamine effects. This competitive inhibition results in reduced basal and nocturnal gastric acid secretion and a reduction in gastric volume, acidity, and amount of gastric acid released in response to stimuli including food, caffeine, insulin, betazole, or pentagastrin.

Famotidine binds competitively to H₂-receptors located on the basolateral membrane of the parietal cell, blocking histamine effects. This competitive inhibition results in reduced basal and nocturnal gastric acid secretion and a reduction in gastric volume, acidity, and amount of gastric acid released in response to stimuli including food, caffeine, H2-receptor antagonists inhibit basal and nocturnal gastric acid secretion by competitive inhibition of the action of histamine at the histamine H2-receptors of the parietal cells. They also inhibit gastric acid secretion stimulated by food, betazole, pentagastrin, caffeine, insulin, and physiological vagal reflex. /Histamine H2-receptor antagonists/

Indications of  Famotidine

• Gastro-esophageal Reflux Disease 
• Heartburn
• Hypersecretion gastric
• Bronchogenic carcinoma
• Duodenal ulcer prophylaxis
• Erosive esophagitis
• Indigestion
• Stomach ulcer
• Upper GI Hemorrhage
• Zollinger-Ellison Syndrome
• Active Duodenal ulcer
• Benign gastric ulcers
• Maintenance therapy Duodenal ulcer
• Relief of heartburn, acid indigestion, and sour stomach
• Treatment for gastric and duodenal ulcers
• Treatment for pathologic gastrointestinal hypersecretory conditions such as Zollinger–Ellison syndrome and multiple endocrine adenomas)
• Part of a multidrug regimen for Helicobacter pylori eradication, although omeprazole may be somewhat more effective.
• Prevention of NSAID-induced peptic ulcers.
• Given to surgery patients before operations to reduce the risk of aspiration pneumonitis.

Contra-Indications of Famotidine

• Clostridium difficile infection
• Inadequate Vitamin B12
• Stomach Cancer
• Liver problems
• Moderate to severe kidney impairment
• Low amount of magnesium in the blood
• Liver problems
• Interstitial Nephritis
• Subacute cutaneous lupus erythematosus
• Hepatic disease, QT prolongation, renal disease, renal failure, renal impairment.
• Systemic lupus erythematosus
• Osteoporosis
• Broken Bone
• Allergies to Proton Pump Inhibitors

Dosage of Famotidine

Strengths: 10 mg, 20 mg; 40 mg; 20 mg/50 mL; 40 mg/5 mL; 10 mg/mL;  20 mg/10 mL

Gastroesophageal Reflux Disease

Oral

• Usual dose: 20 mg orally 2 times day
• Duration of therapy: Up to 6 weeks

Parenteral

• Usual dose: 20 mg IV every 12 hours

Duodenal Ulcer

Oral

• Usual dose: 40 mg orally once a day at bedtime OR 20 mg orally 2 times a day
• Maintenance dose: 20 mg orally once a day at bedtime
• Duration of therapy: 4 weeks

Parenteral

• Usual dose: 20 mg IV every 12 hours

Peptic Ulcer

Oral

• Usual dose: 40 mg orally once a day at bedtime OR 20 mg orally 2 times a day
• Maintenance dose: 20 mg orally once a day at bedtime
• Duration of therapy: 4 weeks

Parenteral

• Usual dose: 20 mg IV every 12 hours

Zollinger-Ellison Syndrome

Oral

• Initial dose: 20 mg orally every 6 hours
• Maximum dose: 160 mg orally every 6 hours

Parenteral

• Usual dose: 20 mg IV every 6 to 12 hours

Dyspepsia

Oral, Over-the-Counter (OTC) Formulations

• Treatment dose: 10 to 20 mg orally once
• Symptom prevention: 10 to 20 mg orally once 10 to 60 minutes prior to consuming food/beverages that cause heartburn
• Maximum dose: 2 tablets/day
• The maximum duration of therapy: 14 days

Pediatric Peptic Ulcer

1 TO 16 years, Oral

• Usual dose: 0.5 mg/kg orally once a day at bedtime OR 0.25 mg/kg orally 2 times a day
• Maximum dose: 40 mg/day

Parenteral

• Initial dose: 0.25 mg/kg IV injected over at least 2 minutes OR infused over 15 minutes every 12 hours
• Maximum dose: 40 mg/day

16 years & older, Oral

• Usual dose: 40 mg orally once a day at bedtime OR 20 mg orally 2 times a day
• Maintenance dose: 20 mg orally once a day at bedtime
• Duration of therapy: 4 weeks

Parenteral

• Usual dose: 20 mg IV every 12 hours

Gastroesophageal Reflux Disease

Less than 3 months, Oral

• Initial dose: 0.5 mg/kg orally once a day
• Duration of therapy: Up to 8 weeks

3 month to less than 1 year, Oral

• Initial dose: 0.5 mg/kg orally 2 times a day
• Duration of therapy: Up to 8 weeks

1 Year to 16 Years, Oral

• Usual dose: 0.5 mg/kg/day orally 2 times a day
• Maximum dose: Up to 40 mg/dose

Parenteral

• Initial dose: 0.25 mg/kg IV injected over at least 2 minutes OR infused over 15 minutes every 12 hours
• Maximum dose: 40 mg/day

16 YEARS AND OLDER Oral

• Usual dose: 20 mg orally 2 times day
• Duration of therapy: Up to 6 weeks

Parenteral

• Usual dose: 20 mg IV every 12 hours

Side Effects of Famotidine

The most common

• Nausea and vomiting
• Severe stomach ache
• Severe diarrhea
• Vaginal thrush
• Skin rash
• Headache
• chest pain
• constipation
• cough
• diarrhea or loose stools
• difficulty with breathing
• dizziness
• heartburn
• muscle pain

More common

• Abdominal or stomach pain, discomfort, or tenderness
• chills or fever
• difficulty with moving
• a headache, severe and throbbing
• joint or back pain
• muscle aching or cramping
• muscle pains or stiffness
• chest pressure or squeezing pain in the chest
• discomfort in arms, shoulders, neck or upper back
• excessive sweating
• feeling of heaviness, pain, warmth and/or swelling in a leg or in the pelvis
• sudden tingling or coldness in an arm or leg
• sudden slow or difficult speech
• sudden drowsiness or need to sleep
• fast breathing
• sharp pain when taking a deep breath
• fast or slow heartbeat
• a coughing up blood
• rust colored urine
• decreased amount of urine

Rare

• Anxiety
• change in vision
• seizures
• abnormal or fast heart rate
• tremors
• weight loss
• chest pain or tightness
• confusion
• cough
• Agitation
• arm, back, or jaw pain
• blurred vision
• chest pain or discomfort
• convulsions
• extra heartbeats
• fainting
• hallucinations
• headache
• irritability
• lightheadedness
• mood or mental changes
• muscle pain or cramps
• muscle spasm or jerking of all extremities

Drug Interactions

Famotidine may interact with following drugs, supplements, & may change the efficacy of drug

• amiodarone
• azole antifungal medications (e.g., fluconazole, ketoconazole)
• caffeine
• calcium channel blockers (e.g., diltiazem, nifedipine, verapamil)
• carbamazepine
• carvedilol
• benzodiazepines (alprazolam, chlordiazepoxide, clonazepam, diazepam,flurazepam, midazolam, and triazolam)
• clopidogrel
• clozapine
• dasatinib
• glyburide (and other “sulfonylurea” diabetes medications)
• lidocaine
• metformin
• metoprolol
• pentoxifylline
• phenytoin
• propranolol
• salmeterol
• SSRIs (e.g., citalopram, fluoxetine, sertraline)
• sucralfate
• theophyllines (e.g., aminophylline, oxtriphylline, theophylline)
• tramadol
• tricyclic antidepressants(e.g., amitriptyline, clomipramine, desipramine, trimipramine)
• warfarin

Pregnancy Catagory

FDA Pregnancy Category B

Pregnancy

The safety of this medication for use during pregnancy has not been established. This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Lactation

You should not take famotidine if you are breastfeeding. It may be excreted in your breast milk and may harm your nursing child.

References

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