View source for H2 receptor antagonists

==Introduction==
H2 receptor antagonists, also known as H2 blockers, are a class of medications that are commonly used in the treatment of conditions that cause excess stomach acid. These include [[Peptic Ulcer Disease|peptic ulcer disease]], [[Gastroesophageal Reflux Disease|gastroesophageal reflux disease]] (GERD), and [[Zollinger-Ellison Syndrome|Zollinger-Ellison syndrome]]. They work by blocking the action of histamine on the parietal cells in the stomach, thereby reducing the production of acid.

[[Image:Detail-58262.jpg|thumb|center|A detailed view of a healthy human stomach.|class=only_on_mobile]]
[[Image:Detail-58263.jpg|thumb|center|A detailed view of a healthy human stomach.|class=only_on_desktop]]

==Mechanism of Action==
H2 receptor antagonists act by selectively blocking the H2 receptors on the basolateral membrane of the gastric parietal cells. This inhibits the action of histamine, a chemical that stimulates the secretion of stomach acid. By blocking the action of histamine, H2 blockers reduce the volume and acidity of the stomach acid, helping to alleviate symptoms and promote healing in conditions associated with excess stomach acid.

==Types of H2 Receptor Antagonists==
There are several types of H2 receptor antagonists that are currently available. These include cimetidine, ranitidine, famotidine, and nizatidine. While they all work in a similar manner, there are differences in their potency, duration of action, and side effect profiles.

===Cimetidine===
[[Cimetidine]] was the first H2 receptor antagonist to be developed and is still widely used today. It is effective in the treatment of peptic ulcer disease, GERD, and Zollinger-Ellison syndrome. However, it has a relatively short duration of action and needs to be taken multiple times a day.

===Ranitidine===
[[Ranitidine]] is another commonly used H2 receptor antagonist. It is more potent and has a longer duration of action than cimetidine, allowing for less frequent dosing. It is also associated with fewer side effects.

===Famotidine===
[[Famotidine]] is one of the most potent H2 receptor antagonists and has a long duration of action. It is often used in the treatment of severe cases of peptic ulcer disease and GERD.

===Nizatidine===
[[Nizatidine]] is similar in potency and duration of action to ranitidine. It is also associated with fewer side effects.

==Clinical Uses==
H2 receptor antagonists are used in the treatment of a variety of conditions that are associated with excess stomach acid. These include:

* Peptic ulcer disease: H2 blockers are effective in promoting the healing of both gastric and duodenal ulcers. They are also used in the prevention of recurrent ulcers.

* Gastroesophageal reflux disease: H2 blockers can help to alleviate the symptoms of GERD, such as heartburn and regurgitation. They can also promote the healing of esophagitis, a condition that is often associated with GERD.

* Zollinger-Ellison syndrome: This is a rare condition that is characterized by the overproduction of stomach acid. H2 blockers can help to control the acid production and alleviate the symptoms.

==Side Effects and Contraindications==
Like all medications, H2 receptor antagonists can cause side effects. These are generally mild and may include headaches, dizziness, and gastrointestinal symptoms such as nausea and diarrhea. In rare cases, they can cause more serious side effects such as confusion, hallucinations, and arrhythmias.

H2 blockers are contraindicated in individuals who are allergic to them. They should also be used with caution in individuals with liver or kidney disease, as these conditions can affect the metabolism and excretion of the drugs.

==Conclusion==
H2 receptor antagonists are a vital tool in the management of conditions associated with excess stomach acid. They have a well-established safety and efficacy profile and are generally well-tolerated. However, like all medications, they should be used judiciously and under the supervision of a healthcare professional.

==See Also==
* [[Proton Pump Inhibitors]]
* [[Antacids]]
* [[Histamine]]

[[Category:Pharmacology]]
[[Category:Gastroenterology]]
[[Category:Medicine]]