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Unit Code 8302:
Quinidine, Plasma

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Useful For

Assessing and adjusting dosage for optimal therapeutic

level

 

Assessing toxicity

Clinical Information

Quinidine is indicated in the treatment of premature atrial and ventricular

contractions, paroxysmal atrial tachycardia, paroxysmal atrioventricular

(A-V) junctional rhythm, and atrial flutter. Quinidine is contraindicated in

A-V block and in digitalis-induced A-V conduction disorders.

 

The dose of quinidine required to achieve optimally effective serum

concentrations is highly variable (in the range of 2.0-5.0 ug/mL).

 

Quinidine is 70% protein bound in plasma with a volume of

distribution of 2.7 L/kg. It undergoes renal clearance at a rate of

5 mL/min/kg with an elimination half-life of 6 to 8 hours.

 

There are no significant active metabolites, and toxicity is invariably

observed when concentrations are > or =7.0 ug/mL. Symptoms of toxicity

include cinchonism, tinnitus, light-headedness, premature ventricular

contractions, and A-V node block. Gastrointestinal distress is a

frequent side effect. It becomes more severe and is associated with

nausea and vomiting at higher blood concentrations.

 

Physiologic processes that generally reduce metabolism and

clearance increase the blood concentration of quinidine.

Co-administration of drugs that activate the cytochrome oxidase

enzymes enhance clearance resulting in lower blood concentrations.

While digoxin co-administration does not affect quinidine

concentration, quinidine does reduce digoxin clearance.

Reference Values

Therapeutic concentration:  2.0-5.0 ug/mL

Toxic concentration:  > or =7.0 ug/mL

Interpretation

Optimal response to quinidine occurs when the serum level is between

2.0 ug/mL to 5.0 ug/mL.

Cautions

No significant cautionary statements

Clinical Reference

Ochs HR, Greenblatt DJ, Woo E: Clinical Pharmacokinetics of quinidine.

Clin Pharmacokinet 1980;5:150-168

Key