Gastric Acid Inhibitors Health Article

Definition

Gastric acid inhibitors are medications that reduce the production of stomach acid. They are different from antacids, which act on stomach acid after it has been produced and released into the stomach.

Purpose

Gastric acid inhibitors are used to treat conditions that are either caused or made worse by the presence of acid in the stomach. These conditions include gastric ulcers; gastroesophageal reflux disease (GERD); and Zollinger-Ellison syndrome, which is marked by atypical gastric ulcers and excessive amounts of stomach acid. Gastric acid inhibitors are also widely used to protect the stomach from drugs or conditions that may cause stomach ulcers. Medications that may cause ulcers include steroid compounds and nonsteroidal anti-inflammatory drugs (NSAIDs), which are often used to treat arthritis. Gastric acid inhibitors offer some protection against the stress ulcers that are associated with some types of illness and with surgery.

Description

There are two types of gastric acid inhibitors, H₂-receptor blockers and proton pump inhibitors. H₂-receptor blockers are a type of antihistamine. Histamine, in addition to its well-known effects in colds and allergies, also stimulates the stomach to produce more acid. The receptors (nerve endings) that respond to the presence of histamine are called H₂ receptors, to distinguish them from the H₁ receptors involved in causing allergy symptoms. The most common H₂-receptor blockers are cimetidine (Tagamet), famotidine (Pepcid), nizatidine (Axid), and ranitidine (Zantac).

The proton pump inhibitors (PPIs) are drugs that block an enzyme called hydrogen/potassium adenosine triphosphatase in the cells lining the stomach. Blocking this enzyme stops the production of stomach acid. These drugs are more effective in reducing stomach acid than the H₂-receptor blockers. The PPIs include such medications as omeprazole (Prilosec), esomeprazole (Nexium), lansoprazole (Prevacid), pantoprazole (Protonix) and rabeprazole (AcipHex).

Recommended dosages

The recommended dosage depends on the specific drug; the purpose for which it is being used; and the route of administration, whether oral or intravenous. Patients should check with the physician who prescribed the medication or the pharmacist who dispensed it. If the drug is an over-the-counter preparation, patients should read the package labeling carefully, and discuss the correct use of the drug with their physician or pharmacist. This precaution is particularly important with regard to the H₂-receptor blockers, because they are available in over-thecounter (OTC) formulations as well as prescription strength. The two are not interchangeable; OTC H₂-receptor blockers are only half as strong as the lowest available dose of prescription-strength versions of these drugs.

Patients should not use the over-the-counter preparations as an alternative to seeking professional care. For some conditions, particularly stomach ulcers, acid-inhibiting drugs may relieve the symptoms, but will not cure the underlying problems, which require both acid reduction and antibiotic therapy.

Gastric acid inhibitors work best when they are taken regularly, so that the amounts of stomach acid are kept low at all times. Patients should check the package directions or ask the physician or pharmacist for instructions on the best way to take the medicine.

Precautions

There are relatively few adverse reactions when gastric acid inhibitors are used for one to two doses before or just after surgery, The side effects listed below are most often seen with long-term use.

H2-receptor blockers

Although the H₂-receptor blockers are very safe drugs, they are capable of causing thrombocytopenia, a disorder in which there are too few platelets in the blood. This deficiency may cause bleeding problems, since platelets are essential for blood clotting. Platelet deficiencies can only be recognized by blood tests; there are no symptoms that the patient can see or feel. In addition to affecting platelet levels, the H₂-receptor blockers may cause changes in heart rate, making the heart beat either faster or slower than normal. Patients should call a physician immediately if any of these signs occur:

• tingling of the fingers or toes
• difficulty breathing
• difficulty swallowing
• swelling of the face or lips
• rapid heartbeat
• slow heartbeat

In addition to these signs, the H₂-receptor blockers may cause the following unwanted reactions:

• headache
• diarrhea
• dizziness
• drowsiness
• nausea
• depression
• skin rash
• vomiting

In addition, cimetidine is an inhibitor of male sex hormones; it may cause loss of libido, breast tenderness and enlargement, and impotence.

Ranitidine may cause loss of hair or severe skin rashes that require prompt medical attention. In rare cases, this drug may cause a reduction in the white blood cell count.

Before using H₂-receptor blockers, people with any of these medical problems should make sure their physicians are aware of their conditions:

• kidney disease
• liver disease
• medical conditions associated with confusion or dizziness