Quinidine Pharmacology

Quinidine

About Quinidine
A cinchona alkaloid, Aryl amino alcohol derivative, Class Ia Antiarrhythmic, antimalarial.
Mechanism of Action of Quinidine
Quinidine has class 1A and class-3 antiarrhythmic properties and antivagal actions. It blocks myocardial Na+ channels in an open state, reduces automaticity, and maximal rate of 0 phase depolarization in a frequency dependent manner. It prolongs action potential duration (APD) due to K+ channel block and lengthens Effective refractory period (ERP) by its moderate effect on recovery of Na+ and K+ channels. At higher concentration it also inhibits L type Ca2+ channels. It reduces availability of Na+ channels as well as delays their activation.
It decreases automaticity in Purkinje fibres and other ectopic foci and this serves to extinguish extra systoles and is important in the prophylaxis of reentrant arrhythmias. It depresses sick sinus also. It increases threshold for excitation. ERP is prolonged more than APD so that ERP/APD is increased. Antivagal action adds to this effect in atrium and minimizes ERP disparity and serves to terminate atrial flutter, atrial fibrillation, and paroxysmal supraventricular tachycardia.
It also has some alpha adrenergic blocking property; so at higher doses dilate blood vessels and cause fall in BP.

Pharmacokinets of Quinidine
Absorption: Well absorbed orally. Distribution: Widely distributed in to the tissues except brain in a plasma protein bound form. Metabolism: Metabolized in liver by hydroxylation. Excretion: Excreted through urine mostly as metabolites and about 20% as unchanged drugs.
Onset of Action for Quinidine
30 to 120 minutes
Duration of Action for Quinidine
6-8 hours
Half Life of Quinidine
6 hours or more
Side Effects of Quinidine
1.Nausea
2.Vomiting
3.Diarrhoea
4.Ringing in ears
5.Deafness
6.Vertigo
7.Headache
8.Visual impairment
9.Mood changes
10.Delirium
11.Arrhythmias
12.Prolongs QRS complex and Q-T intervals
13.Ventricular failure and Cardiac arrest
14.Fever
15.Angioedema
16.Asthma
17.Vascular collapse
18.Thrombocytopenia(rare)
19.Fall in BP
20.Syncope
21.Paradoxical ventricular tachycardia
22.AV block
23.SA block
24.Abdominal pain
25.Allergic manifestations
26.Respiratory arrest
27.Hepatotoxicity

Contra-indications of Quinidine
1.Hypersensitivity to the drug
2.Heart block
3.Long Q-T interval
4.Congestive heart failure
5.Hypotensive state
6.History of embolism
7.Myasthenia gravis
8.Digitalis intoxication

Special Precautions while taking Quinidine
1.Renal impairment
2.Hepatic impairment
3.Asthma
4.Muscle weakness
5.Infection accompanied by fever because hypersensitivity reactions are masked
Pregnancy Related Information
Contraindicated
Old Age Related Information
Use with caution
Breast Feeding Related Information
Contraindicated
Children Related Information
Contraindicated
Indications for Quinidine
1.Atrial fibrillation
2.Atrial flutter
3.Paroxysmal supraventricular tachycardia
4.Atrial arrhythmia
5.Ventricular premature contractions
6.Premature atrial contractions
7.Ventricular tachycardia
8.Maintenance of cardioversion

Interactions for Quinidine
Amiodarone: Increase in quinidine-serum levels which may result in fatal cardiac dysarrhythmias.
Antacids: Increase in quinidine-serum levels resulting in toxicity.
Barbiturates: Decreased serum levels of quinidine.
Cholinergic drugs: May result in failure to terminate paroxysmal supraventricular tachycardia.
Hydantoins: Decrease in efficacy of quinidine may occur.
Nifedipine: Decrease in serum levels of quinidine.
Urinary alkalinizers: Increase in efficacy of quinidine.
Verapamil: Hypotension, bradycardia, ventricular tachycardia, AV block & pulmonary oedema.
Anticholinergics: Additive vagolytic effect.
Anticoagulants: Activity of anticoagulants potentiated, bleeding may occur.
Beta-blockers: Effects of metoprolol or propanolol may be increased.
Cardiac glycosides: Increased pharmacologic effects and toxicity of cardiac glycosides.
Disopyramide: Increased disopyramide levels or decreased quinidine levels may occur.
Non-depolarising muscle blockers: Efficacy enhanced by quinidine.
Procainamide: Increased effects of procainamide with resultant toxicity may occur.
Propafenone: Efficacy of propafenone enhanced.
Succinylcholine: Neuromuscular blockade of succinylcholine may be prolonged.
TCAs: Increased pharmacologic effects of TCAs.
Typical Dosage for Quinidine
First give test dose of 50 to 200mg. Then give 200 to 400mg three times daily or four times daily. Further increase in dose if required until therapeutic response is obtained or toxic effect is started.
Maximum dose: 3 to 4gm/day.
Children: First give test dose of 2mg/kg. Then give 30mg/kg/day in four to six divided doses.

Schedule of Quinidine
H
Storage Requirements for Quinidine
Store at controlled room temperature at a range of 15 to 25 degree C. in a well closed container and protects from light.


Effects of Missed Dosage of Quinidine
Take the missed dose as soon as noticed and if it is the time for next dose then skip the missed dose. Continue the regular schedule. Do not double the dose.
Effects of Overdose of Quinidine
Treatment is supportive and symptomatic. If ingestion was recent remove drug from the body by induced emesis, gastric lavage. Absorption is reduced by administration of activated charcoal. Acidification of urine enhance elimination,. Monitor and support cardiovascular and respiratory functions with haemodynamic and ECG monitoring. Reverse hypotension using metaraminol or nor epinephrine. Perform cardiac pacing. Treat altered Q-T interval with isoproterinol or ventricular pacing. I.V. infusion of 1/6 sodium lactate solution reduces cardiotoxic effect of Quinidine. Rarely haemodialysis may be used.

Home Delivery for Quinidine in Your City

Medicine India is just a publishing medium for medicine related information and does not provide services or sales of medicines including quinidine.

However, we do publish a comprehensive directory of Pharmacies, Chemists and Druggists in cities all over India. You can use this directory to find the medicine stores in your city (or area) that provide home delivery services for quinidine and other medicines and health products. Home delivery services for quinidine may be free or they may cost you depending on the pharmacy and the minimum order requirements. It would be best to get this clarified while placing the order.

Please be aware that you should take quinidine only if a doctor has recommended or prescribed it. Some or all pharmacies who provide a home delivery service for medicines might insist on a prescription for quinidine before they complete the sale. You can get this information while placing the order for quinidine with the pharmacy.

Quinidine is a generic medicine name and there are several brands available for it. Some of the brands for quinidine might be better known than quinidine itself. If the pharmacy that's willing to deliver medicines to your home doesn't have quinidine in stock, you can ask for one of the branded alternatives for quinidine.