Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Disopyramide is approved for treatment of life-threatening ventricular arrhythmia. It is metabolized by hepatic dealkylation to nordisopyramide, which has roughly 25% pharmacological activity compared to the parent drug. The half-life varies depending on formulation (immediate- versus extended-release), with a mean of approximately 7 hours. Disopyramide is largely eliminated in urine, thus doses must be adjusted in patients with reduced renal function.
Therapeutic concentrations of disopyramide are generally in the range of 2.0 to 5.0 mcg/mL. Hepatic dysfunction, renal failure, and congestive heart failure can result in accumulation. Anticholinergic toxicity (dry mouth, urinary hesitancy, blurred vision) is more likely at higher serum concentrations. Other potentially serious adverse effects can include severe hypoglycemia and disruption of cardiovascular function (dysrhythmias, hypotension, edema, or cardiac arrest).
Monitoring for appropriate therapeutic level
Therapeutic concentration is 2.0 to 5.0 mcg/mL.
Arrhythmias may occur at concentrations <2.0 mcg/mL.
Anticholinergic side effects become excessive at concentrations >5.0 mcg/mL.
Severe toxicity occurs with values > or =7.0 mcg/mL.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
No significant cautionary statements
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: 2.0-5.0 mcg/mL
Toxic: > or =7.0 mcg/mL
Clinical References 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. Disopyramide In Physician’s Desk Reference. November, 2009