Proton Pump Inhibitors and H2 Blockers | Actions, Side Effects

Proton pump inhibitors (PPIs) are widely used these days in the treatment of gastritis, second only to antacids. PPIs are very effective in reducing gastric acid secretion. Up until PPIs became available, H2-receptor blockers, commonly known as H2-blockers, were the drug of choice in suppressing acid secretion and reducing the total volume of gastric secretions.

What are Proton Pump Inhibitors?

Proton pump inhibitors (PPIs) are the most effective agents in inhibiting gastric acid secretion. The PPIs can completely inhibit acid production by inactivating H+/K+ATPase (proton pump) present in the parietal cells on the stomach. This pump is responsible for pushing hydrogen into the stomach canaliculi while removing potassium thereby leaving chloride behind to bond with hydrogen and form hydrochloric acid (HCl). More than 90% acid secretion can reduced with a PPI.

The two most commonly used proton pump inhibitors are omeprazole and lansoprazole. Most are available as oral preparations although there are some PPIs that can be administered intravenously. It may be used on its own to treat gastritis or other gastric hyperacidity conditions. It may also be combined with antibiotics to treat H.pylori gastritis or other causes of infectious gastritis. The action of a proton pump inhibitor may last up to 24 hours. It should be used on an empty stomach about half an hour before meals (breakfast or dinner).

Side Effects of Proton Pump Inhibitors

Proton pump inhibitors are fairly safe to use with minimal side effects in a minority of users. Some of the more common side effects reported with the use of proton pump inhibitors include :

What are H2-Receptor Blockers?

H2-receptor blockers, also known as H2-receptor antagonists or simply H2-blockers,  inhibit the action of histamine which stimulates gastric acid secretion. By blocking the histamine-2 (H2) receptors, histamine cannot bind to these sites. H2-blockers also reduce gastric juice volume, along with some reduction in pepsin secretion.

Some of the available H2-blockers include cimetidine, ranitidine, famotidine and nizatidine. These days, cimetidine is not routinely prescribed due to the host of side effects discussed below. Just as with PPIs, H2-blockers are available as oral and intravenous preparations. IV H2-blockers act much more rapidly than oral preparations. Standard doses of H2-blockers have been shown to reduce more than 90% of nighttime acid secretion.

Side Effects of H2-Blockers

Common side effects reported with the use of H2-blockers include :

  • Changes in bowel movement – constipation or diarrhea
  • Headaches
  • Fatigue
  • Muscle pain

More serious side effects include :

  • Bradycardia (low pulse)
  • Hypotension (low blood pressure)
  • Blood dyscrasias (abnormal blood counts)
  • Abnormal liver function (reversible)

Cimetidine Side Effects

High doses or long term use of cimetidine may cause gynecomastia (enlargement of the male breast) or impotence in men and galactorrhea in women. These side effects however, do not occur with the other H2-blockers. Cimetidine can also affect the metabolism of several drugs like phenytoin, warfarin and theophylline. Elderly patients or patients with kidney or liver dysfunction may experience confusion, hallucinations and agitation with the use of intravenous H2-blockers, particularly with cimetidine.

Related Articles

  1. What is Gastritis?
  2. Gastritis Treatment
  3. Helicobacter Pylori Gastritis

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