Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.1.7 (acetylcholinesterase)
 28,390 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The influence of cimetidine on the pharmacokinetic and pharmacodynamic response to the insecticide carbaryl has been investigated in isolated human erythrocytes (red blood cells; RBC) and after oral administration of 1 mg/kg carbaryl to four normal subjects in the absence or presence of cimetidine (300 mg, 8/hr for 3 days). Carbaryl induced a concentration-dependent reduction of isolated RBC acetylcholinesterase activity requiring 1 microgram/ml to achieve 20% inhibition. Cimetidine also induced a dose-dependent inhibition of RBC acetylcholinesterase activity, but at 40-fold higher concentrations. At high concentrations, cimetidine was additive to carbaryl-induced inhibition of RBC acetylcholinesterase, but exhibited no effect at the therapeutically relevant concentrations (10 micrograms/ml). After oral carbaryl administration to normal subjects, plasma concentrations rapidly rose to a peak, then declined with a half-life of 0.79 +/- 0.47 hr. Oral carbaryl clearance was 5.4 +/- 2.0 l/min. Peak plasma carbaryl concentrations were associated with 27% inhibition of RBC acetylcholinesterase activity, and the concentration associated with a reduction of RBC acetylcholinesterase activity of 20% was 0.02 microgram/ml. The terminal half-life for the dynamic response was 2.6 +/- 1.5 hr. After pretreatment with cimetidine, peak plasma carbaryl concentrations doubled and clearance was reduced (to 2.5 +/- 1.5 l/min) (P less than .05). However, half-life remained unchanged. Despite increased carbaryl levels, the maximum inhibition of RBC acetylcholinesterase activity was significantly reduced, and the concentration of carbaryl required to achieve 20% inhibition of RBC acetylcholinesterase activity was increased to approximately 0.5 microgram/ml. These results are consistent with the hypothesis that carbaryl is metabolized by drug-metabolizing enzymes that can be inhibited by cimetidine.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Cimetidine-carbaryl interaction in humans: evidence for an active metabolite of carbaryl. 152 12

Ganglionic effects of the histamine H2 receptor antagonists cimetidine, ranitidine and 1-nitro-2-(2-propynylamino)-2-(2-[dimethylaminomethyl-2-furanyl) methylthiol]-ethylamino)ethylene (ORF 17578) were compared in the isolated superior cervical ganglion of the rat. Extracellular recording of compound action potentials showed that the drugs caused concentration-dependent inhibition of ganglionic transmission, as indicated by depression of the postganglionic compound action potential. Cimetidine-induced inhibition of ganglionic transmission was stimulus frequency-dependent. Increasing the Ca2+ from 2.2 to 4.4 mM in the bathing solution did not significantly affect the inhibitory actions of these agents. In the series with ranitidine, pretreatment with DFP to inhibit acetylcholinesterase similarly had no significant effect on the depression of the compound action potential by ranitidine. All three agents had little or no effect on nerve conduction in isolated vagi of the rat. The results indicate that all three histamine H2 receptor blockers inhibited ganglionic transmission, but only in large concentrations. The results also suggest that the blocking effect of these drugs was unrelated to their reported anticholinesterase action or to blockade of histamine H2 receptors, which are believed to exist on the presynaptic membrane. It is suggested that the ganglion effect may be due to the action of these agents on the acetylcholine receptor-ion channel complex in the postsynaptic membrane.
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PMID:A comparative study of the actions of histamine H2 receptor antagonists on transmission in the isolated superior cervical ganglion of the rat. 197 Jan 32

The cholinomimetic activity of Cimetidine and Ranitidine has been demonstrated by several authors. In the aim to better understand the phenomenon, we analyse the miniature end-plate current decay time. The prolongation of the decay phase of the synaptic current induced by the "selective" H2-antagonist Ranitidine, and to a lesser extent and at higher concentrations by Cimetidine, resembles that of the cholinesterase inhibitors. These agents usually prolong the quantal conductance change having little or no effect on the channel lifetime. The results of our previous experiments, which data were obtained by analyzing the "voltage" events, either spontaneous or evoked, of a classic frog preparation, showed a marked alteration of the temporal parameters. These effects, obtained at higher drug concentrations than those used in the present work, are now better defined by deriving extracellularly the "current" events. The results are also compared with those obtained by assaying the cholinesterase inhibitor Eserine, under the same experimental conditions.
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PMID:A further study on the kinetics of the subcellular current events at the mouse end-plate in the presence of cimetidine and ranitidine. 243 8

Cimetidine increases the duration of action of succinylcholine several-fold by an unknown mechanism. The hydrolysis rate of succinylcholine by human plasma was measured with a modified spectrophotometric assay. At a concentration of 1-50 micrograms/ml cimetidine did not inhibit the hydrolysis of succinylcholine. It is concluded that cimetidine may have an effect at the neuromuscular junction but does not inhibit plasma cholinesterase.
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PMID:Cimetidine does not inhibit plasma cholinesterase activity. 335 73

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

The effect of the H2-receptor antagonists cimetidine and famotidine on interdigestive gastric motor activity and lower esophageal sphincter pressure was assessed in 41 patients with uncomplicated progressive systemic sclerosis. There was no significant change in gastric phasic motor activity after the intravenous administration of cimetidine (n = 6), famotidine (n = 13), and physiological saline (n = 15), or the intragastric infusion of 7% sodium bicarbonate (n = 7). The lower esophageal sphincter pressure was increased significantly by both cimetidine and famotidine, but only famotidine caused a significant pressure rise in patients without an increase of gastric motility. Cimetidine and physiological saline produced a similar pattern of change in the esophageal sphincter pressure, as did famotidine and sodium bicarbonate. These findings suggest that the inhibition of acetylcholinesterase activity and gastric acid secretion may be involved in the respective mechanisms of action of cimetidine and famotidine.
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PMID:Effect of H2-receptor antagonists cimetidine and famotidine on interdigestive gastric motor activity and lower esophageal sphincter pressure in progressive systemic sclerosis. 794 40