THE PET PHARMACY By Wendy C. Brooks, DVM, DipABVP Educational Director, VeterinaryPartner.com

(for veterinary information only)

Available in 75 mg tablets, 150 mg tablets, 300 mg tablets oral syrup 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 it. Until relatively recently, we relied on simply neutralizing stomach acid by pouring alkaline solutions (i.e. 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 an important factor in the treatment of stomach ulcers. Acid secretion is controlled by a hormone called gastrin (secreted in the presence of food and which leads to secretion of stomach acid), acetylcholine (a neurotransmitter), and histamine (that same substance responsible for the unpleasant allergic effects of hay fever.)

Ranitidine is a type of antihistamine similar to cimetidine (Tagamet HB) and famotidine (Pepcid AC). 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. 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. Ranitidine offers an additional benefit in that not only does it act as an effective antacid but it also aids in encouraging normal stomach contractions. When it comes to managing nausea, normal stomach contractions are crucial in preventing food from pooling in the stomach. Stomach distension is a stimulus for vomiting. Ranitidine helps with nausea by addressing both stomach acid and stomach contractions. As an antacid, Ranitidine is between three and 13 times stronger than its predecessor cimetidine.

How this Medication is Used

Ranitidine 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, kidney failure, ingestion of a toxin that could be ulcerating (an over dose of aspirin, for example), any disease involving protracted vomiting, or used chronically in combination with medications that 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 ranitidine could be helpful.

Ranitidine is generally used twice a day and can be used long term.

Side Effects

The H2 blockers as a group have a 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.

Occasionally humans report headache or mental confusion.

Interactions with other Drugs

There are some drugs that are absorbed better in the presence of stomach acid, such as itraconazole or ketoconazole. The dose may require adjustment when used with ranitidine.

Concerns and Cautions

• The dose of ranitidine may require reduction in patients with liver or kidney disease as these diseases tend to prolong drug activities.
 
• It appears that ranitidine is safe for use in pregnancy but should probably be avoided during lactation.
 
• The use of ranitidine can cause a urine dipstick to falsely test positive for protein.

It is our policy not to give dosing information over the Internet.

Date Published: 2/6/2006 11:58:00 AM
Date Reviewed/Revised: 07/23/2009