The Most Decent
Acid Reducing Drugs
Reasons Why I am Using the title decent for H2 receptors
blockers over the other acid reducing drugs Like PPIs and Acid Neutralizing
agent (like NaoH) are pretty obvious in the article go through full article and
You will find the reason.
Agents Included In H2
Receptors Blockers
Cimetidine (Banned due to Aplastic anemia
association) , Famotidine, Ranitidine, and
Nizatidine.
Pharmacokinetics:
All agent except Nizatidine extensively go through first pass
effect and show bio-availability of about 50 %. Nizatidine has little first
pass effect. Goes through both renal and
hepatic elimination. Dose Reduction is required in moderate to severs renal
insufficiency and same with hepatic patients.
Route of Administration and
Dosage
Cimetidine:-Parenteral 200mg/2ml , Oral Liquid
300mg/5ml and Oral tablet dosage form 400-800mg. (But don’t use this banned
drug)
Ranitidine: -Parenteral 1-25mg/ml, tablets
75-50-300.
Famotidine: -IV bolus, Tablets 10-20mg, gel-caps
and suspension 40mg/5ml.
Nizatidine: - Tablets 75 mg tabs and Capsules
150-300 mg.
Cautions in Parenteral
Administration
Main thing to be cared about when administering H2 Receptor
blockers is that they should be administered with slow IV bolus rate (plunger
of injection should not be pressed at one)
and a slow iv infusion rate. The main reason is rapid IV administration
cause sever cardiac event which arise from the action of these drug on Histamine receptor on heart may be fetal for cardiac patients. Although the selectivity
of these drug for H2 receptors is almost 100 % but there is negligible
selectivity for others receptors too which cause this problem.
Pharmacodynamics
The H 2 antagonists
exhibit competitive inhibition at the parietal cell H 2 receptor and suppress basal and
meal-stimulated acid secretion in a linear, dose-dependent manner. They are
highly selective and do not affect H1 or
H3 receptors. The volume of gastric
secretion and the concentration of pepsin are also reduced. On two ways H2
receptor blockers reduce acid secretion first through blocking H2 receptors and
secondly by diminishing the effect of gastrin on gastrin receptors in the
presence of H2 receptor Blockers.
Special
Pharmacodynamics information is they reduces nocturnal (Night) acid secretion (which is mainly
due to histamine) well compare to meal stimulated acid secretion. Because Meal
stimulated acid secretions is dependent on acetyl-choline, gastrin as well as
histamine.
(The Most Decent Drugs)
The title decent which I have given to this class of drug compare
particularly to PPIs is that they are safe for prolong use without any
potential risk of Hyperplasia of Parietal cells. As PPIs block proton pumps on
parietal cells they low acid secretion but at the same time gastrin is
releasing and developing higher and higher in concentration, leading to potential
cause for Hyperplasia of parietal cells which may lead to carcinoma. Other reason which are concerned is
that PPIs prolong use leads to weak bones which may be a bad experience for
geriatric patient as PPIs drastic use is among the older age. And due to the above reasons they are given after for use of PPIs in chronic conditions.
Clinical Uses of H2
Receptor Blockers
1)Peptic Ulcer 2) Non-Ulcer Dyspepsia 3) Gastroesophageal
Reflux Disease (GERD) 4) Stress Related Ulcer
Adverse Drug Reactions
Except cimetidine (which is banned drug now) others H2
receptor blockers are mostly well tolerated have no side effect except for 3%
patients. Cimetidine has the
notorious side effects gynecomastia , impotence and galactorrhea which is due
to tendency of Cimetidine inhibits binding of dihydro-testosterone to androgen
receptors, inhibits metabolism of estradiol, and increases serum prolactin
levels. The ADR due to which Cimetidine
is banned is its tendency of causing aplastic anemia.
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