H2-receptor blocker

Antacids are identified by many trade names and frequently appear in over-the-counter products. There is such a plethora of antacids on the market that even a partial listing of commercial preparations is difficult. 

The primary antacids can be classified as aluminum-containing, magnesium-containing, calcium carbonate-containing, sodium bicarbonate-containing, or a combination of any of these classifications. These drugs are typically taken orally, either as tablets or as a liquid oral suspension. 

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This lack of complete effectiveness led to the hypothesis that a second type of histamine receptor existed. In 1972, Black et al. (55) discovered a new series of antagonists which they called H2 receptor blockers. Burimamide was the first highly effective H2 blocker, but it was poorly absorbed orally. The modified compound, metiamide, had better absorption but was found to cause granulocytopenia (57.58). Finally, cimetidine was tested and found to be a potent and relatively non-toxic antagonist (59). Cimetidine is now widely used clinically to treat duodenal ulcers, Zollinger-Ellison Syndrome and other gastric hypersecretory diseases (32). 

A 55-year-old man who works in the furnace room at a steel foundry has developed chronic peptic ulcer disease that has not responded to treatment with antibiotics and H2 receptor blockers. You are considering giving him an antimuscarinic drug to block gastric acid secretion as adjunctive therapy. What are your concerns regarding the suitability of this treatment for this worker ... 

Drugs that decrease stomach acidity (e.g., antacids, H2 receptor blockers, and proton pump inhibitors) de-... 

Histamine H2-receptor blockers -idine Cimetidine, ranitidine Gastric ulcers (27)... 

On the other hand, drugs may inhibit the metabolism of other drugs. For example, allopurinol (a xanthine oxidase inhibitor that inhibits the synthesis of uric acid) increases the effectiveness of anticoagulants by inhibiting their metabolism. Chloramphenicol (a potent inhibitor of microsomal protein synthesis) and cimetidine (an H2-receptor blocker used in acid-pepsin disease) have similar properties. In addition, drugs may compete with each other in metabolic reactions. In methyl alcohol (methanol) poisoning, ethyl alcohol may be given intravenously to avert methanol-induced blindness and minimize the severe acidosis. Ethyl alcohol competes with methyl alcohol for... 

Pharmaceutical inhibition of gastric acid output (proton pump inhibitor, H2 receptor blocker) may have beneficial effects when combined with an unprotected pancreatin preparation, not only by protection of enzymes during their gastric passage, but also by increasing duodenal pH and thereby improving enzymatic action. (Note that, in chronic pancreatitis, duodenal pH is lower due to impairment of pancreatic bicarbonate secretion, see above). 

Short-term as well as long-term studies with pantoprazole-sodium have proven its excellent efficacy in healing acid-related diseases, preventing relapse, and providing rapid relief from disease-related symptoms. Direct comparison with other anti-secretory drugs showed that pantoprazole-sodium is significantly more effective than H2-receptor blockers and is either equivalent to or better than other clinically used PPIs [39]. 

AMIODARONE H2 RECEPTOR BLOCKERS Cimetidine may t amiodarone levels Uncertain Monitor PR and BP at least weekly until stable. Warn patients to report symptoms of hypotension (lightheadedness, dizziness on standing, etc.). Consider alternative acid suppression therapy... 

ALPHA-BLOCKERS H2 RECEPTOR BLOCKERS 1 efficacy of tolazoline Uncertain possibly 1 absorption Watch for poor response to tolazoline... 

DIPYRIDAMOLE H2 RECEPTOR BLOCKERS Possible 1 bioavailability of dipyridamole Dipyridamole tablets require an acidic environment for adequate dissolution an t in pH of the stomach impairs dissolution and therefore may 1 absorption of the drug t the dose of dipyridamole or consider using an alternative antiplatelet drug... 

CILOSTAZOL H2 RECEPTOR BLOCKERS Cimetidine t cilostazol levels Cimetidine inhibits CYP3A4-mediated metabolism of cilostazol Avoid co-administration... 

SYMPATHOMIMETICS H2 RECEPTOR BLOCKERS t efficacy and adverse effects of sympathomimetics Unclear t hypertensive response dose reduction may be required. Monitor ECG for tachycardias... 

MAOIs H2 RECEPTOR BLOCKERS-CIMETIDINE t plasma concentrations of modobemide (by up to 40%) Due to cimetidine inhibiting its metabolism Reduce dose of modobemide to one-half to one-third of original, then alter as required... 

SSRIs H2 RECEPTOR BLOCKERS -CIMETIDINE t efficacy and adverse effects, e.g. nausea, diarrhoea, dyspepsia, dizziness, sexual dysfunction t bioavailability Use with caution, monitor for t side-effects. 1 dose may be necessary... 

TCAs H2 RECEPTOR BLOCKERS-CIMETIDINE T efficacy and adverse effects, e.g. dry mouth, urinary retention, blurred vision, constipation 1 metabolism Use alternative acid suppression or monitor more closely and i dose. Rapid hydroxylators may be at t risk... 

MIRTAZAPINE H2 RECEPTOR BLOCKERS -CIMETIDINE t mirtazapine levels Inhibition of metabolism via CYP1A2, CYP2D6 and CYPA4 Consider alternative acid suppression, e.g. H2 antagonist (proton pump inhibitors will interact in poor CYP2D6 metabolizers) or monitor more closely for side-effects 1 dose as necessary... 

CARBAMAZEPINE H2 RECEPTOR BLOCKERS -CIMETIDINE, FAMOTIDINE, RANITIDINE t plasma concentrations of phenytoin and risk of adverse effects including phenytoin toxicity, bone marrow depression and skin reactions Inhibition of metabolism via CYP2C9 and CYP2C19 Use alternative acid suppression (e.g. ranitidine) or warn patients that effects last about 1 week. Consider monitoring carbamazepine levels, and adjust dose as necessaiy... 

ERGOT DERIVATIVES H2 RECEPTOR BLOCKERS -CIMETIDINE T ergotamine/methysergide levels with risk of toxicity Inhibition of metabolism via CYP3A4 Avoid co-administration... 

PRAMIPEXOLE, ROPINIROLE H2-RECEPTOR BLOCKER-CIMETIDINE T efficacy and adverse effects of pramipexole 1 renal excretion of pramipexole by inhibition of cation transport system. Inhibition of CYP1A2-mediated metabolism of ropinirole Monitor closely i dose of pramipexole may be required. Adjust dose of ropinirole as necessaiy or use alternative acid suppression, e.g. H2 antagonist proton pump inhibitor (not omeprazole or lansoprazole)... 

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