The P-I-E-N-O Parkinsn's List Drug Database
famotidine / PepcidTM
GASTROINTESTINAL :
Antihyperacidity
Description: Famotidine is an oral and parenteral histamine type 2-receptor antagonist similar to cimetidine and ranitidine. The actions and indications of famotidine differ little from the other agents, except that famotidine is less likely than cimetidine to interact with other drugs. Famotidine is used in the treatment of gastrointestinal disorders. It was approved by the FDA in October 1986. In 1994, the manufacturer filed an NDA for a non-prescription form of famotidine and on April 30, 1995, Pepcid AC ("Acid Controller") became available for OTC use.
Mechanism of Action: Famotidine competitively inhibits the binding of histamine to HA-receptors on the gastric basolateral membrane of parietal cells, reducing basal and nocturnal gastric acid secretions. The drug also decreases the gastric acid response to stimuli such as food, caffeine, insulin, betazole, or pentagastrin. Famotidine reduces the total volume of gastric juice, thus indirectly decreasing pepsin secretion. The drug does not appear to alter gastric motility, gastric emptying, esophageal pressures, biliary secretions, or pancreatic secretions. Famotidine may aid in gastromucosal healing, and it may protect the mucosa from the irritant effects caused by aspirin and nonsteroidal antiinflammatory agents.
Pharmacokinetics: Famotidine is administered orally and parenterally. Bioavailability of famotidine is approximately 4045%. The drug distributes widely throughout the body tissues, although only minimally into CSF. The majority of a famotidine dose is excreted in the urine; 30-35% of the dose is metabolized by the liver. There is a close relationship between famotidine elimination half-life and creatinine clearance. Famotidine elimination half-life is 2.5-4 hours in patients with normal renal function and increases to roughly 24 hours in anuric patients.
CONTRAINDICATIONS/PRECAUTIONS: Famotidine should be used cautiously in patients with hepatic disease or renal disease, such as renal impairment, because the drug can accumulate, causing toxicity. There is a close relationship between elimination half-life and creatinine clearance. Famotidine elimination half-life is 2.5-4 hours in patients with normal renal function and increases to roughly 24 hours in anuric patients. Dosages of famotidine should be reduced in patients with a creatinine clearance of <10 ml/min.
The safety and efficacy of famotidine in children is not known.
Famotidine is secreted into breast milk. Animal studies have documented transient growth depression in immature animals receiving famotidine via breast milk. Famotidine should not be used in women who are breast-feeding.
Famotidine is classified as pregnancy Category B.
DRUG INTERACTIONS: Famotidine does not affect the cytochrome hepatic oxidative metabolism pathway in the same manner as cimetidine does and therefore does not interact with drugs that are metabolized via this pathway. Nevertheless, a small study documented a significant decrease in theophylline clearance with a corresponding increase in theophylline half-life after therapy with famotidine.
Famotidine can reduce the bioavailability of ketoconazole since ketoconazole requires an acidic environment for absorption. Due to the sustained effects of HA-antagonists, separating the time of administration by 1-2 hours does not prevent this interaction from occurring. It may be necessary to substitute fluconazole for ketoconazole in patients requiring therapy with HAantagonists.
Although some in vitro studies have suggested HA-receptor antagonists inhibit gastric alcohol dehydrogenase, a small study of patients receiving treatment for duodenal ulcer with either famotidine or ranitidine did not demonstrate altered ethanol pharmacokinetics.
ADVERSE REACTIONS: Similar to other HA-antagonists, famotidine causes infrequent adverse reactions. The following reactions have occurred in greater than 1% of patients: headache (4.7%) and dizziness (1.3%).
The following GI adverse reactions have occurred in greater than 1% of patients receiving famotidine: diarrhea (1.7%) and constipation (1.2%). Other GI effects that have been reported include nausea/vomiting and abdominal pain.
Reversible mental status changes, including agitation, delirium, hallucinations, hostility, paranoia, depression, insomnia, and disorientation have been reported following famotidine therapy. A review of central nervous system reactions to HA-blockers revealed that the incidence rate varies widely depending on the specific report, and that no single HA-antagonist is more likely to induce CNS reactions than another.I
Dermatologic reactions are rarely reported with famotidine therapy and include urticaria, pruritus, and alopecia. Although a causal relationship has not been established, both acne and xerosis have been reported.
Sexual dysfunction including libido decrease and impotence have been seen during famotidine therapy.
A number of other adverse reactions have been reported with famotidine, although a causal relationship has not been established. These reactions include myalgias, tinnitus, dysgeusia, paresthesias, seizure (1 report), flushing, fever, asthenia, palpitations, orbital edema, and conjunctival injection.
PATIENT INFORMATION:
What do famotidine tablets do?
Famotidine (PepcidTM ) is a type of antihistamine that blocks the release of stomach acid. Famotidine is used to treat gastric and duodenal ulcers. It can relieve ulcer pain and discomfort. Generic famotidine tablets are not yet available.
What should my doctor, dentist, or pharmacist know before I take famotidine?
They need to know if you have any of these conditions:
How should I take this medicine?
Take famotidine tablets by mouth. Follow the directions on the prescription label. Swallow the tablets with a drink of water. If you only take famotidine once a day take it at bedtime. Take your doses at regular intervals. Do not take your medicine more often than directed.
Special precautions for use in children:
This medicine is not for children under 18 years old.
What if I miss a dose?
If you miss a dose, take it as soon as you can. If it is almost time for your next dose, take only that dose. Do not take double or extra doses.
What other medicines can interact with famotidine?
Tell your doctor or pharmacist: about all other medicines you are taking, including non-prescription medicines; if you are a frequent user of drinks with caffeine or alcohol; if you smoke; or if you use illegal drugs. These may affect the way your medicine works. Check before stopping or starting any of your medicines.
What side effects may I notice from taking famotidine?
Side effects with famotidine are infrequent but include:
Let your doctor know if you get any of these side effects.
What do I need to watch for while I take famotidine? Tell your doctor if your ulcer pain does not improve or gets worse. You may need to take this medicine for several days as prescribed before your symptoms improve. Finish the full course of tablets prescribed by your doctor even if you feel better.
Do not self-medicate with aspirin, ibuprofen or other antiinflammatory medicines; these can aggravate your ulcer and may make it bleed.
Do not smoke cigarettes or drink alcohol; these increase irritation in your stomach and can lengthen the time it will take for your ulcers to heal.
If you need to take an antacid you should take it at least 1 hour before or 1 hour after famotidine. Famotidine will not be as effective if taken at the same time as an antacid. If you get black, tarry stools or vomit up what looks like coffee grounds, call your doctor at once. You may have a bleeding ulcer.
Where can I keep my medicine?
Keep out of the reach of children in a container that small children cannot open.
Store at room temperatures below 40C (104F). Throw away any unused medicine after the expiration date.
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