What Is Meclizine HCl?

H2 receptor blocking drugs are mainly used for duodenal ulcers and gastric ulcers. When applied for 6 to 8 weeks, the healing rate is high. Prolonged medication can reduce recurrence. Zollinger-Ellison syndrome requires larger doses. Other diseases with excessive gastric acid secretion, such as gastrointestinal anastomosis ulcer, reflux esophagitis, etc., and bleeding caused by peptic ulcer and acute gastritis are also available.

H2 receptor blocking drugs are mainly used for duodenal ulcers and gastric ulcers. When applied for 6 to 8 weeks, the healing rate is high. Prolonged medication can reduce recurrence. Zollinger-Ellison syndrome requires larger doses. Other diseases with excessive gastric acid secretion, such as gastrointestinal anastomosis ulcer, reflux esophagitis, etc., and bleeding caused by peptic ulcer and acute gastritis are also available.

H2 receptor blockers mainly block H2 receptors in gastric parietal cells, inhibiting basal gastric acid and nocturnal gastric acid secretion, and also inhibit gastric acid secretion caused by gastrin and M receptor agonists. The main H2 receptor blockers are cimetidine, ranitidine, famotidine, nizatidine, rosartidine, and newly marketed ethibutin and mifeditin ^[1] .

Chinese name

H2 receptor blockers

Mainly used

Duodenal ulcer

Pharmacological action

Can inhibit histamine, pentagastrin

Adverse reactions

Occasional constipation, diarrhea

h2 receptor blocking pharmacological effects

This class of drugs competitively antagonizes the H2 receptor and can inhibit gastric acid secretion caused by histamine, pentagastrin, and M choline receptor agonists. Can significantly inhibit the basic gastric acid and food and other factors caused by nocturnal gastric acid secretion. Gastric fluid volume and hydrogen ion concentration decreased after administration. After 4 weeks of treatment, duodenal ulcer healing rate was 77% -92% under endoscopy. The effect of single administration at dinner is similar to or better than that of multiple administrations a day. It has a slower effect on gastric ulcer, and the healing rate is 75% -88% after 8 weeks of treatment. Ranitidine nizatidine inhibits gastric acid secretion 4 to 10 times stronger than cimetidine, and famotidine is 20 to 50 times stronger than cimetidine.

h2 receptors block drug processes

This class of drugs is well absorbed orally, but the elimination of the first pass reduces the bioavailability to 50% to 60%. Elimination of t1 / 2 nizatidine was 1.3 hours, and the other three drugs were 2 to 3 hours. Most drugs are excreted through the kidney in their original form, but the half-life of ranitidine is significantly prolonged in patients with poor liver function.

h2 receptor blocker adverse reactions

These drugs are characterized by stronger and longer-lasting inhibition of gastric acid secretion than anticholinergic drugs, short treatment courses for ulcers, high healing rates, and relatively few adverse reactions. However, if used improperly, serious consequences can still be caused, requiring the attention of the user. The side effects of H2 receptor blockers are as follows.

h2 receptor blocker central nervous system

Some users report that after taking cimetidine, they feel headache, dizziness, mania, speech insufficiency, and hallucinations. This is an inherent and common adverse reaction of these drugs. In particular, elderly patients with poor renal function are prone to mental disorders or delirium when they use large doses, and even coma. Patients with severe liver and liver dysfunction after taking cimetidine at regular doses have a cerebrospinal fluid concentration of 2 Times more likely to cause adverse reactions in the nervous system. After using ranitidine in some patients, the drug can penetrate the blood-brain barrier, causing reversible mental abnormalities, abnormal behaviors, forgetfulness, and unconsciousness, and some patients have mental symptoms such as disorientation, lethargy, and anxiety. The appearance of neurological symptoms is related to the course and dose of medication, and is related to renal insufficiency, mental history, and brain diseases. These symptoms can be alleviated or eliminated if the dosage is appropriately reduced or discontinued.

h2 receptor blocker digestive system

There were dry mouth, bitter mouth, nausea, vomiting, abdominal pain, diarrhea and constipation, and a slight increase in serum aminotransferase. After oral Cimetidine, severe hepatitis, liver necrosis, and steatosis were occasionally seen. The incidence of liver damage caused by cimetidine was approximately 4.2%. For patients with cirrhosis, hepatic coma may occur, and patients with liver disease should pay great attention to the application of this drug. Taking such drugs for a long time can continuously reduce the acidity in the stomach, which is beneficial for bacteria to multiply in the stomach, thereby reducing nitrate in the esophagus to nitrite, forming N-nitroso compounds, and may be in the case of gastric reflux An infection has occurred.

h2 receptor blocker blood system

A few patients had neutrophil deficiency and pancytopenia after taking the drug. And cimetidine and ranitidine can affect the physiological function of bone marrow and even cause aplastic anemia. During the medication, check for blood. Among the adverse reactions of rosatidine acetate, eosinophilia increased and leukopenia decreased. In terms of endocrine and metabolic systems, if cimetidine and ranitidine are taken for a long time, they can cause breast hyperplasia, hyposexuality, and feminization of breasts in male patients because of their obvious anti-androgenic effect. Female patients may experience non-lactation. Galactorrhea. Famotidine can also cause irregular menstruation, galactorrhea and abnormal lipid metabolism, hyperprolactinemia, decreased plasma testosterone levels, and increased gonadotropin levels in women. About 0.38% of patients with nizatidine also had abnormal sexual desire. Long-term use of cimetidine and ranitidine can cause vitamin B12 deficiency. Ranitidine can cause acute episodes of hematoporphyria, and patients with a history of acute hematoporphyria should not use ranitidine.

h2 receptor blockers in cardiovascular system

For example, after use of famotidine, very few patients may experience increased heart rate and induce death from acute myocardial infarction, as well as increased blood pressure; rosartin may also cause increased blood pressure; intravenous injection of ranitidine may cause arrhythmia, manifested as tachycardia Slow, serious is cardiogenic shock, mild atrioventricular block, frequent ventricular premature beats. In addition, there is a case report of cardiac arrest caused by intravenous injection of this drug. Patients with severe illness should be monitored for cardiac function when using ranitidine; bradycardia may occur in patients taking cimetidine orally. Atrial premature beats, or T wave inversion on ECG. The incidence of arrhythmia caused by cimetidine is up to 6.3%, mostly in the elderly. Nizatidine can reduce heart rate and cardiac output, and co-administration with pirenzepine can offset this adverse reaction. ^[1]

H2 receptor blocker preparation and usage

Diphenhydramine hydrochloride (benadryl) tablets, 25-50 mg / time, 3 times / day. Injection, 20 mg / time, intramuscular injection, 1-2 times / day.

Theophylline (dimenhydrinate; theohydramine) tablet is a compound of diphenhydramine and aminophylline to prevent motion sickness. Take 50mg half an hour before the trip.

Promethazine hydrochloride (phenergan) tablets, 1.25 to 25 mg / time, 2 to 3 times / day. Injection, 25-50mg / time, intramuscularly or intravenously.

Pyribenzamine hydrochloride tablets, 25-50mg / time, 3 times / day.

Chlorpheniramine maleate (chlorpheniramine maleate, chlorpheniramine) tablets, 4mg / time, 3 times / day, pediatric 0.35mg / kg · day, divided into 3 to 4 times / day. Injection, 5-20mg / time, subcutaneous or intramuscular injection.

Buclizine hydrochloride (Ann Qimin) tablets, 25-50mg / time, 2 times / day.

Meclizine hydrochloride (meclizine hydrochloride) tablets, 25 mg / time, 2 times / day.

Phenindamine tartrate tablets, 25mg / time, 2-3 times / day.

Astemizole (astemizole) tablets, 10 mg / time, once / day.

Terfenadine tablets, 60 mg / time, 2 times / day.

Cimetidine tablets, 400 mg / time, 3 times / day, or 800 mg, taken after dinner, 1 time / day. Injection, 200 mg / time, intravenous drip, 1 or 2 times / day.

Ranitidine hydrochloride tablets, 150 mg / time, 2 times / day, or 300 mg, taken after dinner, 1 time / day, 4-8 weeks as a course of treatment. Injection, 50mg / time, intramuscular injection or intravenous injection every 6-8 hours.

Famotidine tablets, 20 mg / time, 2 times / day, or 40 mg, taken after dinner, once / day. Injection, 20 mg / time, 2 times / day, intravenous drip.

Nizatidine capsules, 150 mg / time, 2 times / day, or 300 mg, taken after dinner, once / day, 4-8 weeks as a course of treatment.