Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0012833 (dizziness)
 9,689 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The chemistry, pharmacology, pharmacokinetics, clinical efficacy, adverse effects, and dosage of the Class I antiarrhythmic agent moricizine hydrochloride are reviewed. Moricizine is chemically similar to the phenothiazines but does not appear to block dopaminergic receptors. Its major electrophysiologic actions are a concentration-dependent decrease in maximum rate of phase 0 depolarization; increased rates of phase 2 and 3 repolarization, decreased action potential duration, and decreased effective refractory period. Moricizine causes a dose-related prolongation of the PR interval and of AV nodal, infranodal, and intraventricular conduction times but has little effect on ventricular repolarization. The antiarrhythmic and electrophysiologic effects are not correlated with plasma concentrations of the drug or its metabolites. Moricizine reduces the occurrence of ventricular premature contractions (VPCs), couplets, and nonsustained ventricular tachycardia. It appears to suppress symptomatic nonsustained ventricular tachycardia, sustained ventricular tachycardia, and ventricular fibrillation or flutter. Moricizine appears to be as effective as quinidine and more effective than disopyramide, propranolol, and imipramine but less effective than flecainide and encainide at reducing VPCs. Moricizine continues to be evaluated in the Cardiac Arrhythmia Suppression Trial, which was designed to assess the long-term benefit of arrhythmia suppression in patients with left ventricular dysfunction after myocardial infarction. Moricizine seems to be better tolerated than quinidine, disopyramide, and imipramine and to have less proarrhythmic potential than flecainide or encainide. Noncardiac adverse effects include dizziness, nausea, and headache. Cimetidine appears to decrease moricizine clearance, and decreased theophylline clearance has been reported in subjects given moricizine. The usual adult dosage of moricizine hydrochloride is 600-900 mg/day given in three divided doses; an every-12-hour regimen may be used in some patients. Because of the risk of proarrhythmic effects, indications are limited to treatment of documented life-threatening arrhythmias. Moricizine will compete with other agents as first-line therapy for life-threatening arrhythmias.
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PMID:Moricizine: a new class I antiarrhythmic. 227 51

The H2-receptor antagonists which are used for ulcer therapy fall into four main structural classes. Cimetidine is an imidazole derivative; ranitidine belongs to the basically substituted furans, famotidine is a member of the guanidinothiazole group; and roxatidine belongs to the aminoalkylphenoxy series. Famotidine is the most potent, selective H2-receptor antagonist yet available for ulcer therapy. On a weight basis, famotidine is approximately eight times more potent than ranitidine and 40 times more potent than cimetidine. Cimetidine, ranitidine and famotidine are competitive antagonists, while the long-acting H2-receptor antagonists, e.g. loxtidine and lamitidine, are insurmountable H2-receptor blockers. Famotidine has a longer duration of action than either ranitidine or cimetidine. Because famotidine does not interact with cytochrome P-450 of the hepatic enzyme system, it does not appear to affect the metabolism of drugs metabolized by this system. The overall number of side-effects of the H2-receptor antagonists is in the range of 2-3% and no irreversible adverse effects are known. Famotidine has been found to be generally well tolerated. In a first post-marketing study, the number of patients with side-effects was only 0.43%. Side-effects such as headache, dizziness, constipation and diarrhoea have been observed only occasionally. Thus, famotidine is a safe and potent H2-receptor blocker of acid secretion.
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PMID:What are the differences between the H2-receptor antagonists? 290 67

The Oriental flushing reaction is an adverse response to alcohol that appears to be genetically determined. In this study, the Oriental flushing reaction that was produced with ingestion of small amounts of alcohol was antagonized by antihistamine administration. A group of 17 subjects was tested. Each subject received placebo, diphenhydramine 50 mg (H-1 receptor antagonist), and cimetidine 300 mg (H-2 receptor antagonist) singularly and in combination. Alcohol was then administered orally. Most subjects given placebo experienced the typical flushing reaction that included a cutaneous flush, increase in skin temperature, decrease in blood pressure, increase in pulse rate and subjective symptoms such as dizziness, sleepiness, anxiety, headache, generalized weakness, and nausea. The flush, temperature and systolic hypotension were significantly blocked by the combined antihistamine administration. Cimetidine given alone blocked the flush, temperature increase, and systolic hypotension significantly more than diphenhydramine but less than the combined antihistamines. Diphenhydramine was similar to placebo in its effect on the flushing reaction. The role of histamine in the expression of tolerance to alcohol is not known. Antihistamine antagonism of the adverse flushing reaction suggests that histamine receptors may participate in the intolerance to ethanol in Orientals. Histamine may be an important protective factor in the low prevalence of alcoholism in Orientals.
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PMID:Histamine receptor antagonism of intolerance to alcohol in the Oriental population. 368 Dec 77

A 49-year-old woman treated with cimetidine 300 mg tid for more than 18 months for Zollinger-Ellison syndrome experienced lethargy, dizziness, ataxia, and auditory and visual hallucinations after receiving triazolam 0.375 mg hs for sleep. Triazolam plasma concentrations were measured, and a triazolam elimination half-life was calculated to be approximately 8 hours (reported range 1.7-3 h). Cimetidine has been reported to decrease the apparent oral clearance of triazolam, resulting in increased triazolam plasma concentrations with the potential for exaggerated triazolam pharmacologic effects. Cimetidine may have been responsible for the unusually large elimination half-life in this patient. Until the mechanisms and clinical significance of this potential drug interaction are determined, clinicians should use the combination of triazolam and cimetidine with caution.
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PMID:Central nervous system toxicity associated with concurrent use of triazolam and cimetidine. 404 60