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2D Structure
Also known as: 56-54-2, (+)-quinidine, Conquinine, Pitayine, Conchinin, Chinidin
Molecular Formula
C20H24N2O2
Molecular Weight
324.4  g/mol
InChI Key
LOUPRKONTZGTKE-LHHVKLHASA-N
FDA UNII
ITX08688JL

An optical isomer of quinine, extracted from the bark of the CHINCHONA tree and similar plant species. This alkaloid dampens the excitability of cardiac and skeletal muscles by blocking sodium and potassium currents across cellular membranes. It prolongs cellular ACTION POTENTIALS, and decreases automaticity. Quinidine also blocks muscarinic and alpha-adrenergic neurotransmission.
Quinidine is an Antiarrhythmic and Cytochrome P450 2D6 Inhibitor. The mechanism of action of quinidine is as a Cytochrome P450 2D6 Inhibitor.
1 2D Structure

2D Structure

2 Identification
2.1 Computed Descriptors
2.1.1 IUPAC Name
(S)-[(2R,4S,5R)-5-ethenyl-1-azabicyclo[2.2.2]octan-2-yl]-(6-methoxyquinolin-4-yl)methanol
2.1.2 InChI
InChI=1S/C20H24N2O2/c1-3-13-12-22-9-7-14(13)10-19(22)20(23)16-6-8-21-18-5-4-15(24-2)11-17(16)18/h3-6,8,11,13-14,19-20,23H,1,7,9-10,12H2,2H3/t13-,14-,19+,20-/m0/s1
2.1.3 InChI Key
LOUPRKONTZGTKE-LHHVKLHASA-N
2.1.4 Canonical SMILES
COC1=CC2=C(C=CN=C2C=C1)C(C3CC4CCN3CC4C=C)O
2.1.5 Isomeric SMILES
COC1=CC2=C(C=CN=C2C=C1)[C@@H]([C@H]3C[C@@H]4CCN3C[C@@H]4C=C)O
2.2 Other Identifiers
2.2.1 UNII
ITX08688JL
2.3 Synonyms
2.3.1 MeSH Synonyms

1. Adaquin

2. Apo Quinidine

3. Apo-quinidine

4. Chinidin

5. Quincardine

6. Quinidex

7. Quinidine Sulfate

8. Quinora

9. Sulfate, Quinidine

2.3.2 Depositor-Supplied Synonyms

1. 56-54-2

2. (+)-quinidine

3. Conquinine

4. Pitayine

5. Conchinin

6. Chinidin

7. (8r,9s)-quinidine

8. Quinidex

9. Beta-quinine

10. (9s)-6'-methoxycinchonan-9-ol

11. Cin-quin

12. Kinidin

13. Quinora

14. Cinchonan-9-ol, 6'-methoxy-, (9s)-

15. Conchinine

16. Chinidinum

17. Quinidina

18. Chinidine

19. .beta.-quinidine

20. Quinaglute

21. Quiniduran

22. Auriquin

23. Alpha-(6-methoxy-4-quinolyl)-5-vinyl-2-quinuclidinemethanol

24. (s)-[(2r,4s,5r)-5-ethenyl-1-azabicyclo[2.2.2]octan-2-yl](6-methoxyquinolin-4-yl)methanol

25. Quinidine Sulfate

26. Chebi:28593

27. Quinicardine

28. Chembl1294

29. Quinact

30. Quinalan

31. Quinatime

32. (1s)-(6-methoxyquinolin-4-yl)((2r,4s,5r)-5-vinylquinuclidin-2-yl)methanol

33. Itx08688jl

34. 6-methoxy-alpha-(5-vinyl-2-quinuclidinyl)-4-quinolinemethanol

35. Beta-quinidine

36. (3'.alpha., 9s)-6'-methoxycinchonan-9-ol

37. (s)-[(2r,4s,5r)-5-ethenyl-1-azabicyclo[2.2.2]octan-2-yl]-(6-methoxyquinolin-4-yl)methanol

38. Tcmdc-131239

39. Nci-c56246

40. Mfcd00135581

41. (r)-(6-methoxyquinolin-4-yl)((3s,4r,7s)-3-vinylquinuclidin-7-yl)methanol

42. (s)-(6-methoxy-4-quinolyl)-[(2r,4s,5r)-5-vinylquinuclidin-2-yl]methanol

43. (s)-(6-methoxyquinolin-4-yl)((1s,2r,4s,5r)-5-vinylquinuclidin-2-yl)methanol

44. (s)-[(4s,5r,7r)-5-ethenyl-1-azabicyclo[2.2.2]octan-7-yl]-(6-methoxyquinolin-4-yl)methanol

45. Chinidin [german]

46. Smr000857275

47. Quinidine [ban:nf]

48. Unii-itx08688jl

49. Quinindine

50. Ccris 672

51. Hsdb 225

52. (8r,9s)-6'-methoxycinchonan-9-ol

53. (s)-(6-methoxyquinolin-4-yl)((2r,5r)-5-vinylquinuclidin-2-yl)methanol

54. (s)-(6-methoxy-quinolin-4-yl)-((2r,5r)-5-vinyl-1-aza-bicyclo[2.2.2]oct-2-yl)-methanol

55. Qdn

56. Einecs 200-279-0

57. Quinidine, Anhydrous

58. Quinidine [mi]

59. Quinidine [hsdb]

60. Prestwick3_000280

61. Quinidine [vandf]

62. Bmse000511

63. Epitope Id:141803

64. Quinidine [mart.]

65. Quinidine [who-dd]

66. Schembl15943

67. Bspbio_000160

68. Mls001335913

69. Mls001335914

70. Mls002548869

71. Bpbio1_000176

72. Gtpl2342

73. Dtxsid4023549

74. Schembl17537608

75. Hms2234l10

76. Hms3259o09

77. 101143-86-6

78. Act09863

79. Hy-b1751

80. Zinc3831405

81. (9s)-6-methoxy-alpha-(5-vinyl-2-quinuclidinyl)-4-quinolinemethanol

82. Alpha-(6-methoxy-4-quinolyl)-5-vinyl-2-quinuclidinemethanol (9s)-

83. Bdbm50121975

84. Akos015920101

85. Ccg-256507

86. Cs-7812

87. Db00908

88. Nc00478

89. Sdccgmls-0066600.p001

90. Ncgc00091231-01

91. Ncgc00091231-02

92. Ncgc00091231-03

93. Ncgc00091231-18

94. As-30538

95. Quinine Sulfate Impurity A [who-ip]

96. Ab00514657

97. Quinine Bisulfate Impurity A [who-ip]

98. Ab01562940_01

99. Quinine Sulfate Impurity A [ep Impurity]

100. Q412496

101. W-109256

102. Brd-k59632282-052-01-5

103. Brd-k59632282-052-02-3

104. Brd-k70799801-311-02-7

105. Quinine Hydrochloride Impurity A [ep Impurity]

106. Quinidine, Crystallized, >=98.0% (dried Material, Nt)

107. Quinine Bisulfate Heptahydrate Impurity A [who-ip]

108. (s)-((2s,4s,5r)-5-ethenyl-1-azabicyclo(2.2.2)oct-2-yl)(6-methoxyquinolin-4-yl)methanol

2.4 Create Date
2005-06-24
3 Chemical and Physical Properties
Molecular Weight 324.4 g/mol
Molecular Formula C20H24N2O2
XLogP32.9
Hydrogen Bond Donor Count1
Hydrogen Bond Acceptor Count4
Rotatable Bond Count4
Exact Mass324.183778013 g/mol
Monoisotopic Mass324.183778013 g/mol
Topological Polar Surface Area45.6 Ų
Heavy Atom Count24
Formal Charge0
Complexity457
Isotope Atom Count0
Defined Atom Stereocenter Count4
Undefined Atom Stereocenter Count0
Defined Bond Stereocenter Count0
Undefined Bond Stereocenter Count0
Covalently Bonded Unit Count1
4 Drug and Medication Information
4.1 Drug Information
1 of 2  
Drug NameQuinidine sulfate
Drug LabelQuinidine is an antimalarial schizonticide and an antiarrhythmic agent with class 1A activity; it is the -isomer of quinine, and its molecular weight is 324.43. dQuinidine sulfate is the sulfate salt of quinidine; its chemical name is cinchonan-9-ol,...
Active IngredientQuinidine sulfate
Dosage FormTablet, extended release; Tablet
RouteOral
Strength200mg; 300mg
Market StatusPrescription
CompanySandoz; Watson Labs; Teva Pharms; Mutual Pharm

2 of 2  
Drug NameQuinidine sulfate
Drug LabelQuinidine is an antimalarial schizonticide and an antiarrhythmic agent with class 1A activity; it is the -isomer of quinine, and its molecular weight is 324.43. dQuinidine sulfate is the sulfate salt of quinidine; its chemical name is cinchonan-9-ol,...
Active IngredientQuinidine sulfate
Dosage FormTablet, extended release; Tablet
RouteOral
Strength200mg; 300mg
Market StatusPrescription
CompanySandoz; Watson Labs; Teva Pharms; Mutual Pharm

4.2 Therapeutic Uses

Adrenergic alpha-Antagonists; Anti-Arrhythmia Agents; Antimalarials; Enzyme Inhibitors; Muscarinic Antagonists

National Library of Medicine's Medical Subject Headings online file (MeSH, 1999)


Quinidine is indicated in the treatment of recurrent, documented, life-threatening ventricular arrhythmias, such as sustained ventricular tachycardia. Quinidine should not be used to treat ventricular arrhythmias of lesser severity, such as asymptomatic ventricular premature contractions. /Included in US product labeling/

MICROMEDEX Thomson Health Care. USPDI - Drug Information for the Health Care Professional. 22nd ed. Volume 1. MICROMEDEX Thomson Health Care, Greenwood Village, CO. 2002. Content Reviewed and Approved by the U.S. Pharmacopeial Convention, Inc., p. 2482


Quinidine is indicated in the treatment of symptomatic atrial fibrillation or flutter in patients whose symptoms are not controlled by measures to reduce the rate of ventricular response. /US Product Labeling/

MICROMEDEX Thomson Health Care. USPDI - Drug Information for the Health Care Professional. 22nd ed. Volume 1. MICROMEDEX Thomson Health Care, Greenwood Village, CO. 2002. Content Reviewed and Approved by the U.S. Pharmacopeial Convention, Inc., p. 2483


Chronic quinidine treatment is indicated for some patients at high risk for symptomatic atrial fibrillation pr flutter, such as those who have had previous episodes taht are so frequent and poorly tolerated as to outweigh the risk of porphylactic therapy with quinidine. /US Product Labeling/

MICROMEDEX Thomson Health Care. USPDI - Drug Information for the Health Care Professional. 22nd ed. Volume 1. MICROMEDEX Thomson Health Care, Greenwood Village, CO. 2002. Content Reviewed and Approved by the U.S. Pharmacopeial Convention, Inc., p. 2483


Intravenous quinidine is indicated in the treatment of life-threatening Plasmodium falciparum malaria. /US Product Labeling/

MICROMEDEX Thomson Health Care. USPDI - Drug Information for the Health Care Professional. 22nd ed. Volume 1. MICROMEDEX Thomson Health Care, Greenwood Village, CO. 2002. Content Reviewed and Approved by the U.S. Pharmacopeial Convention, Inc., p. 2483


4.3 Drug Warning

Skin reactions to quinidine are rare and include morbilliform and scarlatiniformeruptions, urticaria, rash, pruritus, exfoliative dermatitis, eczema, severe exacerbation of psoriasis, lichenoid reactions, flushing, pigmentary abnormalities, photodermatitis (photosensitivity), and contact dermatitis.

McEvoy, G.K. (ed.). American Hospital Formulary Service - Drug Information 2003. Bethesda, MD: American Society of Health-System Pharmacists, Inc. 2003 (Plus Supplements)., p. 1566


... Adverse reactions are not related to plasma concentration and include drug fever cholestatic hepatitis, systemic lupus erythematosus, asthma, anaphylaxis, thrombocytopenia, hemolytic anemia (especially in glutcose-6-phosphate dehydrogenase deficiency), and hypoprothrombinemia. Skin changes range from maculopapular eruption to thrombocytopenic purpura, cutaneous vasculitis, photosensitivity, and bullous lesions.

Ellenhorn, M.J., S. Schonwald, G. Ordog, J. Wasserberger. Ellenhorn's Medical Toxicology: Diagnosis and Treatment of Human Poisoning. 2nd ed. Baltimore, MD: Williams and Wilkins, 1997., p. 511


Drug induced agranulocytosisis a clinical entity characterized by a selective reduction of circulating neutrophils, usually to a level less than 0.2X10+9/l in relation to the administration of the drug. Quinidine is an antiarrhythmic agent widely used on an outpatient basis with some well known hematological side effects. Its midterm administration has been related to a few cases of agranulocytosis. The case of a 60 yr old man with atrial fibrillation is described who presented quinidine induced agranulocytosis of abrupt onset only 3 days after the exposure to the drug, recovering normal levels of neutrophils during the third hospitalization day.

PMID:2117328 Sureda A et al; Acta Haematol 84 (1): 43-4 (1990)


Large doses ...increase temporal dispersion of ventricular refractory periods ...may induce idioventricular impulse generation. Caution ...mandatory in ...treatment of ventricular ectopic rhythms; increased dose after therapeutic failure may increase hazard.

Goodman, L.S., and A. Gilman. (eds.) The Pharmacological Basis of Therapeutics. 5th ed. New York: Macmillan Publishing Co., Inc., 1975., p. 689


For more Drug Warnings (Complete) data for QUINIDINE (34 total), please visit the HSDB record page.


4.4 Drug Indication

For the treatment of ventricular pre-excitation and cardiac dysrhythmias


FDA Label


5 Pharmacology and Biochemistry
5.1 Pharmacology

Quinidine, a hydantoin anticonvulsant, is used alone or with phenobarbital or other anticonvulsants to manage tonic-clonic seizures, psychomotor seizures, neuropathic pain syndromes including diabetic neuropathy, digitalis-induced cardiac arrhythmias, and cardiac arrhythmias associated with QT-interval prolongation.


5.2 MeSH Pharmacological Classification

Muscarinic Antagonists

Drugs that bind to but do not activate MUSCARINIC RECEPTORS, thereby blocking the actions of endogenous ACETYLCHOLINE or exogenous agonists. Muscarinic antagonists have widespread effects including actions on the iris and ciliary muscle of the eye, the heart and blood vessels, secretions of the respiratory tract, GI system, and salivary glands, GI motility, urinary bladder tone, and the central nervous system. (See all compounds classified as Muscarinic Antagonists.)


Antimalarials

Agents used in the treatment of malaria. They are usually classified on the basis of their action against plasmodia at different stages in their life cycle in the human. (From AMA, Drug Evaluations Annual, 1992, p1585) (See all compounds classified as Antimalarials.)


Cytochrome P-450 CYP2D6 Inhibitors

Drugs and compounds which inhibit or antagonize the biosynthesis or actions of CYTOCHROME P-450 CYP2D6. (See all compounds classified as Cytochrome P-450 CYP2D6 Inhibitors.)


Voltage-Gated Sodium Channel Blockers

A class of drugs that inhibit the activation of VOLTAGE-GATED SODIUM CHANNELS. (See all compounds classified as Voltage-Gated Sodium Channel Blockers.)


Adrenergic alpha-Antagonists

Drugs that bind to but do not activate alpha-adrenergic receptors thereby blocking the actions of endogenous or exogenous adrenergic agonists. Adrenergic alpha-antagonists are used in the treatment of hypertension, vasospasm, peripheral vascular disease, shock, and pheochromocytoma. (See all compounds classified as Adrenergic alpha-Antagonists.)


Anti-Arrhythmia Agents

Agents used for the treatment or prevention of cardiac arrhythmias. They may affect the polarization-repolarization phase of the action potential, its excitability or refractoriness, or impulse conduction or membrane responsiveness within cardiac fibers. Anti-arrhythmia agents are often classed into four main groups according to their mechanism of action: sodium channel blockade, beta-adrenergic blockade, repolarization prolongation, or calcium channel blockade. (See all compounds classified as Anti-Arrhythmia Agents.)


Enzyme Inhibitors

Compounds or agents that combine with an enzyme in such a manner as to prevent the normal substrate-enzyme combination and the catalytic reaction. (See all compounds classified as Enzyme Inhibitors.)


5.3 FDA Pharmacological Classification
5.3.1 Active Moiety
QUINIDINE
5.3.2 FDA UNII
ITX08688JL
5.3.3 Pharmacological Classes
Cytochrome P450 2D6 Inhibitor [EPC]; Cytochrome P450 2D6 Inhibitors [MoA]; Antiarrhythmic [EPC]
5.4 ATC Code

C - Cardiovascular system

C01 - Cardiac therapy

C01B - Antiarrhythmics, class i and iii

C01BA - Antiarrhythmics, class ia

C01BA01 - Quinidine


5.5 Absorption, Distribution and Excretion

Route of Elimination

When the urine pH is less than 7, about 20% of administered quinidine appears unchanged in the urine, but this fraction drops to as little as 5% when the urine is more alkaline.


Volume of Distribution

2 to 3 L/kg

0.5 L/kg [congestive heart failure]

3 to 5 L/kg [cirrhosis of the liver]


Clearance

3 5 mL/min/kg [adults]


The volume of distribution of quinidine is 2 to 3 L/kg in healthy young adults, but this may be reduced to as little as 0.5 L/kg in patients with congestive heart failure, or increased to 3 or 5 L/kg in patients with cirrhosis of the liver. At concentrations of 2 to 5 mg/L (6.5 to 16.2 umol/L), the fraction of quinidine bound to plasma proteins (mainly to (alpha)1-acid glycoprotein and to albumin) is 80 to 88% in adults and older children, but it is lower in pregnant women, and in infants and neonates it may be as low as 50 to 70%. Because (alpha)1-glycoprotein levels are increased in response to stress, serum levels of total quinidine may be greatly increased in settings such as acute myocardial infarction, even though the serum content of unbound (active) drug may remain normal. Protein binding is also increased in chronic renal failure, but binding abruptly descends toward or below normal when heparin is administered for hemodialysis.

Medical Economics Co; Physicians Desk Reference 56th ed p. 2933 (2002)


...Essentially completely absorbed after oral admin; max effects occur within 1-3 hr, and persist for 6-8 more hr. Large fluctuations in plasma concentration... if repeated doses are given at this interval. ...IM admin... gluconate yields peak effects in 30-90 min.

Goodman, L.S., and A. Gilman. (eds.) The Pharmacological Basis of Therapeutics. 5th ed. New York: Macmillan Publishing Co., Inc., 1975., p. 291


...All administered compound is excreted by kidney, and about 10-50% appears in urine as unchanged quinidine, within 24 hr.

Goodman, L.S., and A. Gilman. (eds.) The Pharmacological Basis of Therapeutics. 5th ed. New York: Macmillan Publishing Co., Inc., 1975., p. 692


The bioavailability of quinidine is 70 to 80% after oral use but varies between individuals and preparations. The sulfate salt is rapidly absorbed in 60 to 90 minutes. Polygalacturonate salts produce peak quinidine concentrations in 5 to 6 hours; gastrointestinal absorption of gluconate salts is intermediate (peak 3-4 hours).

Ellenhorn, M.J., S. Schonwald, G. Ordog, J. Wasserberger. Ellenhorn's Medical Toxicology: Diagnosis and Treatment of Human Poisoning. 2nd ed. Baltimore, MD: Williams and Wilkins, 1997., p. 510


For more Absorption, Distribution and Excretion (Complete) data for QUINIDINE (14 total), please visit the HSDB record page.


5.6 Metabolism/Metabolites

Lactate conjugates of quinidine and its 3-hydroxy metabolite were detected in overdose suicide patient.

Leferink et al; J Anal Toxicol 1 (2): 62-5 (1977)


Quinidine is metabolized in the liver, principally via hydroxylation to 3-hydroxyquinidine and 2-quinidinone. Some metabolites have antiarrhythmic activity. Approximately 10-50% of a dose is excreted in urine (probably by glomerular filtration) as unchanged drug within 24 hr.

McEvoy, G.K. (ed.). American Hospital Formulary Service - Drug Information 2003. Bethesda, MD: American Society of Health-System Pharmacists, Inc. 2003 (Plus Supplements)., p. 1571


Quinidine metabolites include 3-hydroxyquinidine N-oxide, 2'-oxoquinidinone, desmethylquinidine, and quinidine N-oxide. While metabolism is highly variable between individuals, at least in cases of quinidine-induced torsade de pointes, the metabolites do not appear to contribute to the formation of dysrhythmias.

Ellenhorn, M.J., S. Schonwald, G. Ordog, J. Wasserberger. Ellenhorn's Medical Toxicology: Diagnosis and Treatment of Human Poisoning. 2nd ed. Baltimore, MD: Williams and Wilkins, 1997., p. 510


Quinidine undergoes extensive hepatic oxidative metabolism... One metabolite, 3-hydroxyquinidine, is nearly as potent as quinidine in blocking cardiac sodium channels or prolonging action potentials.

Hardman, J.G., L.E. Limbird, P.B., A.G. Gilman. Goodman and Gilman's The Pharmacological Basis of Therapeutics. 10th ed. New York, NY: McGraw-Hill, 2001., p. 966


Most quindiidne is eliminated hepatically via the action of cytochrome P450 IIIA.

Medical Economics Co; Physicians Desk Reference 56th ed p. 2933 (2002)


Quinidine has known human metabolites that include 3-Hydroxyquinidine and Quinidine-N-oxide.

S73 | METXBIODB | Metabolite Reaction Database from BioTransformer | DOI:10.5281/zenodo.4056560


5.7 Biological Half-Life

6-8 hours


Quinidine generally has a plasma half-life of 6-8 hr in healthy inividuals, but half-life may range from 3-16 hr or longer. In one study in patients with Plasmodium falciparum malaria, the elimination half-life of the drug averaged 12.8 hr (range: 6.6-24.8 hr).

McEvoy, G.K. (ed.). American Hospital Formulary Service - Drug Information 2003. Bethesda, MD: American Society of Health-System Pharmacists, Inc. 2003 (Plus Supplements)., p. 1571


The usual plasma half-life of approximately 7 hours after intravenous administration is increased in the presence of chronic liver disease.

Ellenhorn, M.J., S. Schonwald, G. Ordog, J. Wasserberger. Ellenhorn's Medical Toxicology: Diagnosis and Treatment of Human Poisoning. 2nd ed. Baltimore, MD: Williams and Wilkins, 1997., p. 510


5.8 Mechanism of Action

Quinidine acts on sodium channels on the neuronal cell membrane, limiting the spread of seizure activity and reducing seizure propagation. The antiarrhythmic actions are mediated through effects on sodium channels in Purkinje fibers. Quinidine may also act on 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.


The exact mechanism of antiarrhythmic action of quinidine has not been determined conclusively, but the drug is considered a class I (membrane stabilizing) antiarrhythmic agent. Like other class I antiarrhythmic agents, quinidine is believed to combine with fast sodium channels in their inactive state and thereby inhibit recovery after repolarization in a time- and voltage-dependent manner, which is associated with subsequent dissociation of the drug from the sodium channels. Quinidine exhibits electrophysiologic effects characteristic of class IA antiarrhythmic agents. The electrophysiologic characteristics of the subgroups of class I antiarrhythmic agents may be related to quantitative differences in their rates of attachment to and dissociation from transmembrane sodium channels, with class IA agents exhibiting intermediate rates of attachment and dissociation.

McEvoy, G.K. (ed.). American Hospital Formulary Service - Drug Information 2003. Bethesda, MD: American Society of Health-System Pharmacists, Inc. 2003 (Plus Supplements)., p. 1570


Like lidocaine and procainamide, quinidine suppresses automaticity in the His-Purkinje system. In usual doses, quinidine may decrease the automaticity of ectopic pacemakers, but the extent of this effect also depends upon the anticholinergic effect of the drug on the sinoatrial node, atria, and atrioventricular node. Extremely high concentrations of quinidine may increase myocardial automaticity. The drug decreases conduction velocity in the atria, ventricles, and His-Purkinje system, and may decrease or cause no change in conduction velocity through the AV node. Quinidine probably suppresses atrial fibrillation or flutter by prolonging the effective refractory period and increasing the action potential duration in atrial and ventricular muscle and in the His-Purkinje system. Because prolongation of the effective refractory period is greater than the increase in the duration of the action potential, the cardiac tissue remains refractory even after restoration of the resting membrane potential. Quinidine shortens the effective refractory period of the atrioventricular node, and the anticholinergic action of the drug may also increase the conductivity of the atrioventricular node. The effects of quinidine on refractoriness and the action potential duration of atrial fibers may be modified by the anticholinergic effects of the drug. Quinidine decreases cardiac excitability, both in diastole and in the relative refractory period, by increasing the threshold potential for electrical excitation. At therapeutic plasma concentrations, quinidine causes prolongation of the QRS complex and QT interval.

McEvoy, G.K. (ed.). American Hospital Formulary Service - Drug Information 2003. Bethesda, MD: American Society of Health-System Pharmacists, Inc. 2003 (Plus Supplements)., p. 1570


Quinidine also exhibits some antipyretic and oxytocic properties. Quinidine has a very weak curare-like action on the myoneural junction and also causes depression of skeletal muscle action potential.

McEvoy, G.K. (ed.). American Hospital Formulary Service - Drug Information 2003. Bethesda, MD: American Society of Health-System Pharmacists, Inc. 2003 (Plus Supplements)., p. 1570


Intravenous quinidine depresses contractility and decreases systemic vascular resistance primarily by alpha-adrenergic receptor blockade. High blood levels of quinidine increase left ventricular end-diastolic pressure through its negative inotropic effect. Cardiovascular collapse has resulted from depression of contractility.

Ellenhorn, M.J., S. Schonwald, G. Ordog, J. Wasserberger. Ellenhorn's Medical Toxicology: Diagnosis and Treatment of Human Poisoning. 2nd ed. Baltimore, MD: Williams and Wilkins, 1997., p. 511


Quindine primarily kills the schizont parasite at the asexual intra-erythrocytic cycle stage of the Plasmodium falciparum malaria protozoan parasite. Quinidine also kills the gametocyte parasite stages of Plasmodium malariae, Plasmodium vivax, and Plasmodium ovale.

MICROMEDEX Thomson Health Care. USPDI - Drug Information for the Health Care Professional. 22nd ed. Volume 1. MICROMEDEX Thomson Health Care, Greenwood Village, CO. 2002. Content Reviewed and Approved by the U.S. Pharmacopeial Convention, Inc., p. 2483