ANSWER
H2 receptor blockers, also known as H2 receptor antagonists (H2RAs), are a type of gastric acid-suppressing agent that is commonly used in a variety of gastric conditions. They are FDA-approved for treating uncomplicated gastroesophageal reflux disease (GERD), gastric or duodenal ulcers, gastric hypersecretion, and mild to infrequent heartburn or indigestion in the short term. Off-label uses of H2RAs include stress ulcer prevention, esophagitis, gastritis, gastrointestinal hemorrhage, and urticaria. H2RAs are also sometimes used as part of a multidrug regimen to treat Helicobacter pylori. Although antacids are usually the first-line treatment for heartburn during pregnancy, H2RAs are pregnancy category B with no known teratogenic effects and can be used if necessary. The overall therapeutic efficacy of H2RAs is highly dependent on the severity of the gastric disease, the dosage regimen, and the duration of therapy. This activity discusses the indications, contraindications, and administration of H2 blockers, as well as the role of the interprofessional team in promoting their safety.
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Objectives:
Determine the mode of action of H2 blockers.
Explain the negative effects of H2 receptor blockers.
Examine the H2 blocker indications.
Outline some interprofessional team strategies for improving care coordination and communication in order to improve H2 blocker safety and outcomes.
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Indications
H2 receptor blockers, also known as H2 receptor antagonists (H2RAs), are a type of gastric acid-suppressing agent that is commonly used in a variety of gastric conditions. They are FDA-approved for treating uncomplicated gastroesophageal reflux disease (GERD), gastric or duodenal ulcers, gastric hypersecretion, and mild to infrequent heartburn or indigestion in the short term. Off-label uses of H2 receptor antagonists include stress ulcer prevention, esophagitis, gastritis, gastrointestinal hemorrhage, and urticaria. These drugs are also sometimes used as part of a multidrug regimen to treat Helicobacter pylori. [1]
Although antacids are usually the first-line treatment for heartburn during pregnancy, H2 receptor antagonists are pregnancy category B with no known teratogenic effects and can be used if necessary.
[2] H2RAs have also been shown to be safe in children and adolescents who have mild or infrequent heartburn symptoms that do not respond to lifestyle changes.
[3] The overall therapeutic efficacy of H2RAs is heavily influenced by the severity of the gastric disease, the dosage regimen, and the duration of therapy.
In the United States, there are currently three FDA-approved H2RA agents available either over-the-counter (OTC) or by prescription only. Famotidine and cimetidine are available without a prescription or over-the-counter, depending on the dose. Nizatidine is only available with a prescription. Ranitidine was previously available, but it has since been withdrawn in the US and suspended in Europe and Australia due to carcinogen contamination during manufacturing. [4] [5]
Navigate to: Mechanism of Action
H2RAs reduce gastric acid secretion by reversibly binding to histamine H2 receptors on gastric parietal cells, thereby inhibiting the endogenous ligand histamine’s binding and activity. As a result, H2 blockers act as competitive antagonists. Gastrin normally stimulates histamine release from enterochromaffin-like cells after a meal, which then binds to histamine H2 receptors on gastric parietal cells and causes gastric acid release. The activation of adenylate cyclase, which raises intracellular cAMP levels, causes an increase in gastric acid release. cAMP then activates protein kinase A (PKA), which phosphorylates proteins involved in the movement of H+/K+ ATPase transporters to the plasma membrane, among other things. The increased number of H+/K+ ATPase transporters at the plasma membrane allows for more acid secretion from parietal cells.
H2RAs suppress both stimulated and basal gastric acid secretion induced by histamine by blocking the histamine receptor and thus histamine stimulation of parietal cell acid secretion.
[6] H2RAs provide gastric relief in about 60 minutes and have a duration of action ranging from 4 to 10 hours, making them useful for on-demand treatment of occasional symptoms. All H2RAs work similarly to reduce gastric acid secretion. [7]
Navigate to: Administration
H2 receptor antagonists are well absorbed following oral administration, and all H2RAs are available as an oral tablet. Nizatidine can also be taken as a capsule or as an oral solution. One of the most commonly used agents is famotidine, which is available as a chewable tablet, oral powder for suspension, or in combination formulations with calcium carbonate, magnesium hydroxide, or ibuprofen. Famotidine is one of the H2RAs that is available as an intravenous solution for use in hospitals.
H2 receptor antagonists can be used as needed to relieve gastric symptoms or as a preventative measure 30 to 60 minutes before known food or beverage triggers. H2RAs can also be combined with antacids to provide both immediate relief of symptoms and a longer duration of action. Patients should take H2RAs once daily at bedtime for the best results. The more common twice-daily doses can be taken in the morning and at night. [7] Patients should not use H2RAs for more than two weeks without consulting their primary care physician first.
Visit: Adverse Effects
In general, H2 receptor antagonists are well tolerated. Mild side effects include headaches, drowsiness, fatigue, abdominal pain, constipation, and diarrhea. [8] H2RA use has been linked to central nervous system side effects such as delirium, confusion, hallucinations, or slurred speech in patients with renal impairment, hepatic impairment, or who are over 50 years old. Cimetidine is generally thought to be the most common cause of these symptoms, though famotidine has also been linked to similar effects. [9] [10] [11]
It is possible that drugs will interact with H2 receptor antagonists. The absorption of drugs that require an acidic environment for dissolution may be altered as a result of the therapeutic increase in gastric pH. Cimetidine is a strong cytochrome P450 (CYP450) enzyme inhibitor and should be avoided when combined with theophylline, selective serotonin reuptake inhibitors, or warfarin. Cimetidine at high doses for an extended period of time has also been linked to gynecomastia, decreased sperm count, and impotence in men, as well as galactorrhea in women. This condition usually clears up after the drug is stopped. Cimetidine is now generally avoided as a therapeutic recommendation for gastric symptoms by clinicians. [12]
Using H2 receptor antagonists on a regular basis may cause tachyphylaxis or tolerance, limiting their use as GERD maintenance therapy. Tolerance to the effects of H2RAs can develop after 7 to 14 days of treatment. H2RAs taken intermittently or as needed may help prevent the development of tachyphylaxis. [13]
In comparison to proton pump inhibitors, H2RAs pose only a minor risk of bacterial overgrowth and infection.
[14]
Visit: Contraindications
H2RAs currently have no absolute contraindications. They should not, however, be used in patients who have a known hypersensitivity to any H2RA or other drug component. Patients should discontinue use of OTC H2RAs if they have difficulty swallowing food, are vomiting blood, or have bloody or black stools. They should instead seek appropriate medical attention.
Visit: Monitoring
To assess clinical effectiveness and the need for therapy adjustments, patients taking H2RAs should be monitored for endoscopic improvement and decreased gastric symptoms. Patients should be monitored for side effects and potential drug interactions, especially if they are taking cimetidine.
H2RAs are removed from the body through a combination of hepatic and renal metabolism. For patients with a creatine clearance of less than 50 mL/min, famotidine and nizatidine doses must be adjusted, whereas cimetidine doses must be reduced for patients with a creatine clearance of less than 30 mL/min. Cimetidine’s half-life may be prolonged in patients with hepatic impairment, but no dose adjustments are required for hepatic impairment unless it is also accompanied by renal impairment.
QT prolongation or central nervous system effects have been observed on rare occasions in patients with impaired renal function whose dose was not properly adjusted. When combined with other QT-prolonging medications or conditions, famotidine should be used with caution. Elderly patients should also be monitored for central nervous system side effects like dizziness or confusion that could be caused by decreased drug clearance. [15]
Visit: Toxicity
Because H2 receptor antagonists have a broad therapeutic index, severe toxicity is uncommon. H2RA toxicity may be linked to H2 receptor inhibition in the myocardium and central nervous system. Central nervous system depression, hypotension, and bradycardia have been reported infrequently, and are usually caused by a rapid intravenous infusion of an H2RA. Toxicities associated with H2RA use may be treated with gastric lavage or activated charcoal, drug discontinuation, and supportive care measures.
Visit: Improving Healthcare Team Outcomes
Many healthcare professionals prescribe H2 blockers, and there are also over-the-counter agents in the class. While these drugs are relatively safe, when combined with other CNS drugs, they can have serious side effects. When using H2 receptor blocking therapy, patient education by the pharmacist, nurse, and clinician, working as an interprofessional healthcare team, is critical to preventing toxicity and driving improved patient outcomes. Pharmacists would be wise to check for drug interactions and even question patients in the retail setting if they come across someone buying H2 receptor antagonists over-the-counter. Patients should be advised not to combine these agents with other CNS drugs/alcohol and to avoid using them for extended periods of time.
QUESTION
Instructions: Please, list the below info for at least one anti-H2 Blocker medication.
Indications
Mechanism of action
What to monitor
Patient variables
Side effects
Adverse effects
Teaching
Requirements:
Formatted and cited in current APA 7
Use 3 academic sources. Not older than 5 years
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Plagiarism is NOT allowed