What's this
Famotidine is a competitive, selective and reversible antagonist of histamine H2 receptors; this drug reduces the secretion of hydrochloric acid in the stomach, inhibiting, in fact, the access of histamine to its binding site in H2 receptors distributed in the gastrointestinal tract; consequently, the production of hydrochloric acid mediated by histamine is lost. Famotidine, in particular, inhibits both basal and hydrochloric acid secretion.
For what you use
Famotidine is indicated in the treatment of duodenal ulcer, gastric ulcer, gastroesophageal reflux disease, Zollinger-Ellison syndrome and ulcers caused by prolonged use of Non-Steroidal Anti-inflammatory Drugs.
Famotidine is marketed under various registered specialty names, such as Pepcidine ®, Pepcid ®, Gaster ® and Gastridin ®, while the most commonly used name for the generic drug is that of the molecule itself: Famotidine.
History
Famotidine was developed by Yamanouchi Pharmaceutical Co. and has been patented by Merck & Co. Merck & Co. then decided to market the drug in collaboration with Johnson & Johnson; the first famotidine-based product was marketed in 1981 under the name Pepcid.
Almost twenty years later, in 1999, a new pharmaceutical form of famotidine was introduced into the market, in the form of an orosoluble soluble tablet, under the name of Pepcid RPD. The marketing of generic preparations of famotidine became possible in 2001 and among the first pharmaceutical companies that started to produce these preparations we can mention Schwarz (its product was called Fluxid) or Gedeon Richter Ltd. (which used the name Quamatel).
In the United States of America a product is found that contains both famotidine and an antacid, thus combining the effects of both active ingredients for a better pharmacological profile; this product is called Pepcid Complete and is marketed as chewable tablets; the same product is also sold in Great Britain under the name of Pepcidtwo.
Features
Famotidine has, in its structure, a thiazole ring replaced in position 2 by a guanidine, while the progenitor of the H2 antagonists - cimetidine - has an imidazole ring replaced in position 2 by a simple methyl. This main difference between the two structures seems to give famotidine a pharmacological potency 30 times higher than that of cimetidine.
The one just described is not the only advantage of famotidine; in fact, its improved chemical structure does not interfere with the cytochrome P450 enzyme system, so - unlike cimetidine - it does not seem to interact with other drugs metabolised by cytochrome P450.
A defect of the molecule is linked to its low bioavailability (about 50% compared to molecules of the same class); it is also slightly soluble in the acid pH of the stomach. For this reason, researchers have developed new drug delivery systems, such as delayed release or continuous release tablets, which greatly improve the bioavailability of famotidine-based drugs.
How to use
Posology and method of use
Duodenal ulcer treatment
In the treatment of duodenal ulcer the recommended dose is 40 mg famotidine per day, to be taken in a single administration, in the evening, before bedtime. The duration of treatment can vary from four to eight weeks; the treatment can be stopped prematurely only if a complete healing of the ulcer is observed, verified by endoscopic examination. Referring to clinical data it can be said that most patients suffering from duodenal ulcer and treated with famotidine recover in 4 weeks; much lower are the cases for which it becomes necessary to continue the treatment for another 4 weeks, until complete recovery. To avoid relapse of the duodenal ulcer it is recommended to continue with maintenance therapy, taking 20 mg / day of famotidine in a single administration, in the evening before going to bed. The maximum recommended duration of maintenance therapy is 6 months, and it is essential that it be prescribed and monitored by a specialized doctor for the entire treatment period.
GASTRIC ulcer treatment
In the therapy for healing of gastric ulcer the recommended dose is 40 mg / day of famotidine, to be taken in single administration, in the evening before going to bed. Based on many clinical experiences, the duration of treatment required for healing varies from 6 to 8 weeks; once again, this treatment can be interrupted only if a complete regression of the ulcer is observed by gastroscopy.
Treatment of Zollinger-Ellison syndrome
The treatment of Zollinger-Ellison syndrome is a little more complicated. First, in patients whose Zollinger-Ellison syndrome has not previously been treated with an antisecretory drug therapy, it is recommended to start treatment with 20 mg famotidine to be given every 6 hours. Then, based on the individual response of the patient, and on the basis of acid secretion, we proceed by regulating the dose used for a continuous treatment, until a satisfactory response is obtained in terms of reduction of acid secretion in the stomach.
During the treatment of Zollinger-Ellison syndrome with famotidine it came to use doses of 640 mg / day for an extended period up to 1 year, without registering the appearance of significant side effects. However, if there is no satisfactory reduction in the secretion of hydrochloric acid in the stomach through doses of famotidine up to 800 mg / day, it is recommended to evaluate alternative treatments with other H2 antagonists or with proton pump inhibitors; this is because to date there is no clinical experience of treatment with doses higher than 800 mg / day.
Treatment of gastroesophageal reflux disease
In the treatment of gastroesophageal reflux disease the recommended dose of famotidine is 40 mg / day divided into two daily administrations, one in the morning and one in the evening, before going to bed. The recommended duration of treatment is 6 weeks. In more serious cases, a dose increase of up to 80 mg / day of famotidine can be used, maintaining the double daily administration: one in the morning and one in the evening; if the doctor considers it necessary, the treatment can be extended up to 12 weeks. However, both the dose and duration of treatment can be reduced when complete recovery is ascertained. To avoid a possible relapse, in more serious cases, it is recommended to continue with a maintenance treatment by taking a dose of famotidine equal to 40 mg / day, to be divided into two daily administrations, one in the morning and one in the evening, before to sleep.
OTHER USES
Famotidine can also be administered intravenously (there are special bottles available on the market) when it is necessary to reduce gastric secretion but it cannot be used orally; this is the case, for example, of patients suffering from hemorrhage of the upper gastrointestinal tract. The recommended dosage, in this case, is 20 mg famotidine every 12 hours.
The bottle should be dissolved in a compatible solvent (the most used is water for injections) and the duration of the injection should not be less than 2 minutes. Alternatively, the bottle can be dissolved in 100 ml of 5% glucose solution or physiological solution (0.9% sodium chloride) and administered by intravenous infusion; the recommended administration time rises, in this case, to about 30 minutes. However, it is advisable to replace the intravenous treatment with oral treatment as soon as possible.
Contraindications and warnings
Before starting the treatment of gastric ulcer with famitidine it is essential to ascertain - using appropriate diagnostic methods - that the symptoms complained of by the patient are not linked to a malignant gastric neoformation ; famotidine, in fact, relieving pain and masking the symptoms of the aforementioned disease, can make it more difficult to correctly diagnose it in useful times.
It is also advisable that in patients suffering from gastric ulcer or duodenal ulcer, before starting therapy with famotidine proceed to ascertain the presence or absence of Helicobacter pylori ; in this way the patient can be subjected to eradication therapy from the beginning, greatly increasing the chance of recovery. Famotidine should not be administered to people with a known hypersensitivity to the same molecule or other components of the pharmaceutical preparation; in case of hypersensitivity manifestations during the treatment the treatment must be suspended and a doctor consulted.
Given that famotidine is primarily eliminated via the kidneys, and partly metabolised via the liver, caution should be exercised when treating patients with moderate or severe renal insufficiency and liver failure . In patients with severe hepatic impairment a reduction in the recommended daily dose is recommended, or an increase in the dose interval from 36 to 48 hours. Furthermore, as with most drugs, particular attention should be paid in case of administration to elderly patients, especially for prolonged treatments, for which it is advisable to undergo a severe medical check-up to avoid the appearance of side effects that could arise. due to prolonged use of famotidine. However, based on data collected from different clinical studies, there was no increase in the incidence of related adverse effects during famotidine treatments of elderly patients.
If famotidine is administered together with substances whose absorption is affected by gastric pH, a possible change in the absorption of these substances should be considered. For example, famotidine may reduce the absorption of antifungal agents such as ketoconazole or itraconazole; therefore it is recommended to administer these drugs about 2 hours before taking famotidine.
On the other hand, the simultaneous intake of famotidine and antacids can lead to a reduction in the absorption of famotidine itself; therefore, if both drugs are to be administered at the same time, it is advisable to take famotidine about 1-2 hours before the antacid.
Pregnancy and breastfeeding
Referring to the patients treated with famotidine during pregnancy, even if their number is limited, it was found that there were no undesirable effects on the course of the pregnancy or on the health of the fetus or newborn. Other animal studies have reported no adverse effects or harm on pregnancy, embryonic development, fetus or postnatal development. In one study, eight mothers who had recently given birth were given 40 mg of famotidine; it has been shown that the molecule is excreted in breast milk, in particular, at a distance of 6 hours after administration the average levels of famotidine in breast milk were 72 mcg / Liter. Unfortunately these are the only data that exist regarding the use of famotidine during pregnancy and lactation; therefore, before starting a famotidine therapy it is recommended to consult your doctor to discuss related benefits and risks for mother and baby.
Side effects
All drugs can cause side and side effects, but most patients do not experience these effects during various treatments.
In general, famotidine is very well tolerated by our body; however, several side effects have been reported. The most frequent ones concern the gastrointestinal tract and include diarrhea (the most frequent), abdominal pain, nausea, vomiting, constipation and anorexia. Besides these, other frequent side effects are related to the central nervous system, such as headache (which affects about 5% of patients treated with famotidine), dizziness and rarely nervousness. Going forward we can mention the less frequent side effects, such as dermatological (like skin rash, itching and hives), those related to the cardiovascular system (such as palpitations or thrombocytopenia), alteration of liver enzymes, fever, hypersensitivity with hyperemia of the conjunctiva, fatigue, dry mouth and musculoskeletal pains.
