What is the difference between histamine blocker and antihistamine

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Do I Need Another Endoscopy? Question I underwent an endoscopic exam about 1 year ago and was diagnosed with gastroesophageal reflux disease GERD. This information is in no way intended to replace the guidance of your doctor. All Rights Reserved. About GERD. What is GERD? H2 Blockers. Unwanted actions H2 antagonists have been so widely used that many side effects are attributed to them, although not necessarily caused by them.

Safety has not been proven in pregnant women and the drugs appear in breast milk. Use H2 antagonists are effective in most cases of heartburn that do not respond to life-style measures. Summary Histamine H2 blockers inhibit the action of histamine on gastric H2 receptors thereby decreasing gastric acidity.

Share this page. Share on facebook. Share on twitter. Share on linkedin. Share on email. Share on print. Topics of this article. Was this article helpful? Make a donation. Related Information. June 30, Another class of drugs that block H1-receptors are the tricyclic antidepressants or TCAs, typically used to treat depression. For example, doxepin Silenor is a TCA that due to its side effect of sedation is often used to treat insomnia.

Ref 3, 4 and 6. The second-generation of H1-receptor antagonists were developed in order to avoid the drowsy effects of the first class. These antihistamines have the same actions as the first-generation but are known for less daytime drowsiness, dry mouth, and confusion.

Used to treat daytime seasonal allergy symptoms, members of this class are loratidine Claritin , cetirizine Zyrtec , and the eye drops olopatadine ophthalmic Pataday. According to an article published in the "Journal of Allergy and Clinical Immunology" in April , the third-generation of H1-blockers have even less effects on the brain then even the second-generation and greater blockage from histamine release from mast cells.

This class of drugs are made from the second-generation in forms called metabolites, which is easier for the body to use. Metabolites are by-products of medications that have been broken down by the body in the cells. Some of the medications in this class are levocetirizine Xyzal which comes from cetirizine, desloratadine Clarinex the metabolite of loratadine, and fexofenadine Allegra which was developed from terfenadine which is no longer on the market.

See ref 2,3, 4, 6, 9. While H1-receptors are in the brain, blood vessels, skin and air passages, H2-receptors are found largely in the stomach lining. Stimulation of H2-receptors signals cells in the stomach walls to secrete gastric acids. H2-blockers were specifically designed to lower the secretion of these acids and help alleviate heartburn symptoms as well as prevent GERD or stomach ulcers from forming.

Not having immediate effects, these drugs can take 60 to 90 minutes before they work, and even then symptoms may not begin to resolve for 2 weeks. Ref 5 and 9. See ref 5 and 9. Background: Histamine is responsible for the wheal and flare reaction in various allergic conditions.

Classical antihistamines are the drugs which block the H 1 receptors and are widely used in various allergic conditions, whereas H 2 blockers are mainly used for acid peptic disease. Although H 1 receptor-mediated actions of histamine are primarily responsible for vasodilatation, vasopermeability, and itching, it has been observed that combined blocking of both H1 and H2 receptors may provide better relief. Aim: To compare the efficacy of levocetirizine H1 blocker versus levocetirizine and ranitidine H2 blocker in suppressing histamine-induced wheal.