Assessing and adjusting dosage for optimal therapeutic level
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Quinidine is indicated for atrial fibrillation and flutter, and life-threatening ventricular arrhythmia. Optimal serum concentrations are in the range of 2.0 to 5.0 mcg/mL, with toxicity apparent at levels > or =6.0 mcg/mL. Symptoms of toxicity (cinchonism) include tinnitus, light-headedness, premature ventricular contractions, and atrioventricular block. Gastrointestinal distress is a frequent side effect, which becomes more severe and is associated with nausea and vomiting at higher drug concentrations.
The half life of quinidine is 6 to 8 hours, and the drug lacks any significant active metabolites. Physiologic processes that generally reduce hepatic metabolism and renal clearance increase serum quinidine levels, while comedication with cytochrome p450 (CYP) enzyme inducers enhances clearance and results in lower blood concentrations.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
Therapeutic concentration: 2.0-5.0 mcg/mL
Toxic concentration: > or =6.0 mcg/mL
Optimal response to quinidine occurs when the serum level is between 2.0 to 5.0 mcg/mL.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Valdes R Jr, Jortani SA, Gheorghiade M: Standards of laboratory practice: cardiac drug monitoring. National Academy of Clinical Biochemistry. Clin Chem 1998;44(5):1096-1109
2. Qunidine. In Physician's Desk Reference (online) Accessed November, 2009