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Query: UMLS:C0018681 (headache)
 56,091 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

In the United States, the drugs most commonly used to treat peptic ulcer disease are antacids and the H2-receptor antagonists cimetidine and ranitidine. Other available agents include anticholinergics and the coating agent sucralfate. Investigational drugs such as colloidal bismuth, carbenoxolone, prostaglandins, the tricyclic compound pirenzepine, and substituted benzimidazoles are not available for use in the United States. Most of the commercially available and investigational compounds have similar efficacy; therefore the optimal drug may be the one associated with the fewest adverse effects and the most convenient dosing regimen. Cimetidine causes a small number of adverse effects, including neuropsychiatric disorders, gynecomastia, impotence, loss of libido, elevation of serum creatinine and serum transaminases concentrations, and drug interactions. Some of these reactions have been of clinical significance. Presently, there are rare reports of gynecomastia, bradycardia, inhibition of acetylcholinesterase, headache, lethargy, diarrhea, and rash in patients receiving ranitidine. Antacids can produce either diarrhea or constipation and have been associated with low serum phosphorus concentrations, and metabolic alkalosis. Anticholinergics, especially in elderly or debilitated patients, can cause central nervous system disorders, intestinal atony, or urinary retention. Sucralfate may cause constipation, diarrhea, nausea, and headache. The investigational agents have their own side effect profiles. The adverse effects of anticholinergics make them unattractive therapeutic choices, and antacids and sucralfate have inconvenient dosing requirements compared with some equally efficacious alternatives. In addition, clinical experience with sucralfate in the United States is limited. The safety record of cimetidine is admirable. As clinical experience with ranitidine increases, currently unrecognized adverse effects may be reported. However, based on current data, ranitidine is as effective as cimetidine and is associated with a lower incidence of side effects.
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PMID:Problems associated with medical treatment of peptic ulcer disease. 609 62

Plasma and urine histamine levels were measured during sequential infusions of histamine (0.05, 0.1, 0.25, 0.5, and 1.0 microgram/kg/min histamine base for 30 min each) to determine the plasma level required to elicit flushing, headaches, tachycardia, and diastolic hypotension. Each study was performed with subjects on no medications or after pretreatment with hydroxyzine and/or cimetidine in order to confirm the receptor subtype involved in each of the responses. Resting plasma histamine levels were 0.62 +/- 0.12 ng/ml, and levels rose progressively indirect proportion to the concentration of infused histamine. Plasma levels of histamine required to elicit symptoms were as follows: 1.61 +/- 0.30 ng/ml = 30% increase in heart rate, 2.39 +/- 0.52 ng/ml = significant flush and headache, and 2.45 +/- 0.13 ng/ml = 30% increase in pulse pressure. Cimetidine pretreatment failed to influence the histamine level required to elicit symptoms, hydroxyzine pretreatment significantly raised the level required to increase heart rat by 30%, and the combination of antihistamines significantly raised the threshold for histamine to elicit all the response. Urine histamine was increased in direct proportion to the histamine infusions, and because of stability, accessibility, and the capacity for retrospective diagnosis, urine is the suggested fluid to employ to measure histamine release in humans.
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PMID:Effects of infused histamine: correlation of plasma histamine levels and symptoms. 612 Sep 67

Impromidine (SK&F 92676), a potent selective histamine H2-receptor agonist in animals has been studied in healthy male volunteers. Impromidine 10 micrograms kg-1h-1 i.v. produced near maximal acid secretion and cimetidine 2 mg kg-1h-1 inhibited this output by a mean of 65% in 5 subjects. The log dose-response curve to impromidine in 5 subjects was linear over the dose range 2.5--20 micrograms kg-1h-1. Cimetidine 0.5 mg kg-1h-1 caused a highly significant parallel shift of the dose-response curve, consistent with direct competitive antagonism. The gastric secretory responses to impromidine 10 micrograms kg-1h-1 i.v., histamine acid phosphate 40 micrograms kg-1h-1 i.v., and pentagastrin 6 micrograms kg-1h-1 i.v. were similar. Cardiovascular effects of impromidine were less marked than those due to histamine. Gastric secretory and cardiovascular effects of impromidine are dose dependent. No significant difference was seen in peak acid output between impromidine 10 micrograms kg-1 and pentagastrin 6 micrograms kg-1 whether injected intramuscularly or subcutaneously. Headache which accompanied infusion with histamine occurred less frequently with impromidine, and nausea and abdominal discomfort which occurred with pentagastrin did not occur with impromidine. Impromidine will be valuable in the study of gastric secretion and the role of histamine H2 receptors in other systems.
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PMID:Gastric secretory studies in humans with impromidine (SK&F 92676)--a specific histamine H2 receptor agonist. 615 65

A syndrome involving periodic fever, pharyngitis, adenitis and aphthous stomatitis is described in 8 children. Attacks are characterized by abrupt onset of fever and, in addition to the above symptoms, by malaise, headache and abdominal pain. Mild leukocytosis and elevation of the erythrocyte sedimentation rate are found in the laboratory. Patients exhibit normal growth and development and are otherwise healthy. PFAPA is clinically benign, with no long-term sequelae. Recognition and diagnosis of the syndrome eliminate the need for intensive work-up. The cause remains unknown. No evidence linking bacterial, viral, or fungal pathogens to this syndrome has been found. No patient has exhibited atypical lymphocytosis or neutropenia, and all patients had normal levels of immunoglobulin. All had received antibiotics early in the course of their illness but without effect. Cimetidine has been discussed in the literature as a possible treatment, but the results are controversial.
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PMID:[PFAPA syndrome: periodic fever, adenitis, pharyngitis and aphthous stomatitis]. 933 38