(for veterinary information only)

BRAND NAME: PEPCID AC

AVAILABLE IN  
10 mg           
TABLETS       
AND  INJECTABLE

BACKGROUND

Stomach ulceration in humans is a prominent medical condition and there has long been pressure to develop effective and convenient ways to address this problem. Until relatively recently, we relied on simply neutralizing stomach acid by pouring alkaline solutions (ie alka seltzer, Tums, Rolaids etc.) into the stomach.  In fact, ulceration is a complicated process and there are many ways to address it.

Control of stomach acid is a very important factor in the treatment of stomach ulcers. Acid secretion is controlled by a hormone called “gastrin” (secreted in the presence of food and leads to secretion of stomach acid), acetylcholine (a neurotransmitter), and histamine (that same substance responsible for the unpleasant allergic effects of  “hay fever.”)

Famotidine is a special antihistamine as are its cousins cimetidine (Tagamet HB) and Ranitidine (Zantac). They are not useful in combating allergic symptoms where histamine causes its unpleasant effects by binding so-called “H1” receptors. Instead they bind to histamine receptors in the stomach called “H2” receptors.

Cimetidine was the first such “H2 blocker” available and each generation has brought about improvements in terms of fewer drug interactions and stronger effect. Famotidine is the longest lasting of the H2 blockers (usually one dose lasts 24 hours). Famotidine is 32 times stronger in its ability to inhibit stomach acid than is cimetidine and is 9 times stronger than ranitidine. A newer H2 blocker called Nizatidine is soon to become available which may offer the additional advantages of especially rapid onset of action and some effect on normalizing stomach contractions as well.

HOW THIS MEDICATION IS USED

Famotidine is useful in any situation where stomach irritation is an issue and ulceration is a concern.  It is often used in the treatment of Helicobacter infection, inflammatory bowel disease, canine parvovirus, ingestion of a toxin that could be ulcerating (over dose of aspirin, for example), any disease involving protracted vomiting, or chronically in combination with medications which may have stomach irritating properties.

In diseases involving frequent vomiting or regurgitation, the esophagus (tube connecting the mouth and stomach) can be ulcerated by continuing exposure to vomit/stomach acid.  Antacids are also helpful in this type of situation to reduce damage to the esophagus. Megaesophagus would be a condition where a long acting antacid such as famotidine could be helpful.

SIDE EFFECTS

The H2 blockers as a group have a very limited potential for side effects, hence their recent release to “over the counter” status.

There  have been some reports of exacerbating heart rhythm problems in patients who already have heart rhythm problems so it may be prudent to choose another means of stomach acid control in heart patients.

INTERACTIONS WITH OTHER DRUGS

There are some drugs that are absorbed better in the presence of stomach acid (example: itraconazole). The dose may require adjustment in the presence of famotidine.

CONCERNS AND CAUTIONS

The dose of famotidine may require reduction in patients with liver or kidney disease as these diseases tend to prolong drug activities.

It appears that famotidine is safe for use in pregnancy but should probably be avoided during lactation.