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Histamine-2 Blockers

Cimetidine (Tagamet), famotidine (Pepcid), nizatidine (Axid), and ranitidine (Zantac) are examples of histamine-2 (H2) blockers. Several of these drugs can be purchased without a prescription in low doses to treat mild, occasional heartburn. Higher doses require a doctor’s prescription.

• How H2 blockers work: These drugs decrease the amount of acid produced by the stomach.
  
  
• Who should not use these medications: Individuals who have experienced an allergic reaction to H2 blockers should not take them.
  
  
• Use: Various dosage regimens are used. If using an over-the-counter nonprescription product, carefully follow the directions for use on the package. For prescription-strength products, your doctor will direct you on how to take the medication. H2 blockers are available in tablet, capsule, and oral liquid forms.
  
  
• Drug or food interactions: Many drugs interact with H2 blockers (particularly with cimetidine). If you take other medications, ask your doctor or pharmacist for information on interactions with H2 blockers. These drugs decrease the body’s ability to excrete caffeine. Individuals who consume large quantities of caffeine may experience tremors, insomnia, or heart palpitations. Cimetidine may increase the likelihood of alcohol intoxication.
  
  
• Side effects: Confusion, depression, and hallucinations have been reported, particularly in elderly individuals or those who are unable to adequately excrete the drugs (for example, people with kidney disease). High doses taken over a long period of time have caused breast enlargement and sexual dysfunction in men. Rarely, H2 blockers cause liver toxicity or decreased platelet counts. (Platelets are blood cells that form clots and decrease bleeding.) If you take these drugs regularly, your doctor will monitor your blood for adverse effects.