| Stereochemistry | ABSOLUTE |
| Molecular Formula | 2C20H24N2O2.5H2O |
| Molecular Weight | 738.9099 |
| Optical Activity | UNSPECIFIED |
| Defined Stereocenters | 10 / 10 |
| E/Z Centers | 0 |
| Charge | 0 |
SHOW SMILES / InChI
SMILES
O.O.O.O.O.[H][C@@]1(C[C@@H]2CC[N@]1C[C@@H]2C=C)[C@@H](O)C3=C4C=C(OC)C=CC4=NC=C3.[H][C@@]5(C[C@@H]6CC[N@]5C[C@@H]6C=C)[C@@H](O)C7=C8C=C(OC)C=CC8=NC=C7
InChI
InChIKey=FNLHOUVTTYMUSI-ZHKFODEYSA-N
InChI=1S/2C20H24N2O2.5H2O/c2*1-3-13-12-22-9-7-14(13)10-19(22)20(23)16-6-8-21-18-5-4-15(24-2)11-17(16)18;;;;;/h2*3-6,8,11,13-14,19-20,23H,1,7,9-10,12H2,2H3;5*1H2/t2*13-,14-,19+,20-;;;;;/m00...../s1
Quinidine is a pharmaceutical agent that acts as a class I antiarrhythmic agent (Ia) in the heart. It is a stereoisomer of quinine, originally derived from the bark of the cinchona tree. The drug causes increased action potential duration, as well as a prolonged QT interval. Like all other class I antiarrhythmic agents, quinidine primarily works by blocking the fast inward sodium current (INa). Quinidine's effect on INa is known as a 'use-dependent block'. This means at higher heart rates, the block increases, while at lower heart rates, the block decreases. The effect of blocking the fast inward sodium current causes the phase 0 depolarization of the cardiac action potential to decrease (decreased Vmax). Quinidine also blocks the slowly inactivating, tetrodotoxin-sensitive Na current, the slow inward calcium current (ICA), the rapid (IKr) and slow (IKs) components of the delayed potassium rectifier current, the inward potassium rectifier current (IKI), the ATP-sensitive potassium channel (IKATP) and Ito. Quinidine is also an inhibitor of the cytochrome P450 enzyme 2D6 and can lead to increased blood levels of lidocaine, beta blockers, opioids, and some antidepressants. Quinidine also inhibits the transport protein P-glycoprotein and so can cause some peripherally acting drugs such as loperamide to have central nervous system side effects, such as respiratory depression if the two drugs are coadministered. Quinidine can cause thrombocytopenia, granulomatous hepatitis, myasthenia gravis, and torsades de pointes, so is not used much today. Torsades can occur after the first dose. Quinidine-induced thrombocytopenia (low platelet count) is mediated by the immune system and may lead to thrombocytic purpura. A combination of dextromethorphan and quinidine has been shown to alleviate symptoms of easy laughing and crying (pseudobulbar affect) in patients with amyotrophic lateral sclerosis and multiple sclerosis. This drug is marketed as Nuedexta in the United States. Intravenous quinidine is also indicated for the treatment of Plasmodium falciparum malaria. However, quinidine is not considered the first-line therapy for P. falciparum. The recommended treatments for P. falciparum malaria, according to the Toronto Notes 2008, are a combination of either quinine and doxycycline or atovaquone and proguanil (Malarone). The drug is also effective for the treatment of atrial fibrillation in horses.
CNS Activity
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Sample Use Guides
Tablet (sulfate):100 to 600 mg/dose orally every 4 to 6 hours; begin at 200 mg/dose and titrate to desired effect (maximum daily dose: 3 to 4 g).
Extended Release: 324 to 648 mg (gluconate) orally every 8 to 12 hours or 300 to 600 mg (sulfate) orally every 8 to 12 hours.
IV: 800 mg of quinidine gluconate diluted to 50 mL and given at a rate not to exceed 1 mL/min.
Route of Administration:
Other
Rat brain pericytes were plated onto the backside of 12-well Transwell filters (pore size: 0.4 μm; 1.5 × 104 cells/filter). The next day, endothelial cells were plated onto the upper surface of the filters. After reaching confluency, the endothelial monolayer was supplied with 550 nM hydrocortisone, 250 μM CPT-cAMP, and 17.5 μM RO-201724 and placed into dishes containing glial cultures for 24 h. Transwell filters containing endothelial cells and pericytes were removed from the plates containing the glial culture. Filters were washed with Ringer-HEPES solution (pH 7.4). Quinidine or digoxin was applied at final concentrations of 0.1 μM and 10 μM, respectively. Radiolabeled quinidine and digoxin as tracers were also added to the radioactive concentration of 1 μCi/mL. The inhibitors were added together with the test compound at final concentrations of 1 μM (LY- 335979 and PSC-833) or 100 μM (quinidine). Samples were taken from the basolateral or apical side, respectively, at 15, 30, and 60 min, and radioactivity was measured using a liquid scintillation counter
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