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Unit Code 500600:
Quinidine, Serum

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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 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 6-8 hours.

 

There are no significant active metabolites, and toxicity is invariably

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

toxicity include cinchonism, and A-V node block. Gastrointestinal

distress is a frequent side effect, which becomes more severe and is

associated with nausea and vomiting at higher blood concentrations.

 

Physiologic processes that generally reduce quinidine metabolism and

clearance increase the blood concentration. Coadministration of drugs

that activate the cytochrome oxidase enzymes enhance clearance

resulting in lower blood concentrations. While digoxin coadministration

does not affect quinidine concentration, quinidine does reduce digoxin

clearance.

Reference Values

Therapeutic concentration:  2.0-5.0 mcg/mL

Toxic concentration:  > or =7.0 mcg/mL

Interpretation

Optimal response to quinidine occurs when the serum level is between

2.0 and 5.0 ug/mL.

Cautions

No significant cautionary statements.

Clinical Reference

1.     Valdes Jr R, Jortani S, Gheordhiade M: Standards of laboratory

      practice: cardiac drug monitoring. Clin Chem 1998 May;44(5):

      1096-1109

 

2.     Grace A, Camm AJ: Therapy, Quinidine. New Engl J Med

      1998 Jan 1;338(1):35-45

 

3.     Krishna S, White NJ: Pharmacokinetics of quinine, chloroquine,

      and amodiaquine. Clinical Implications. Clin Pharmacokinet

      1996 Apr;30(4):263-299            

 

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