: Quinidine, Serum or Plasma

: What This Test Measures

: Quinidine is an antiarrhythmic medicine prescribed to help control abnormal heart rhythms. This test measures how much quinidine is present in your serum or plasma, the liquid part of your blood, so your clinician can see whether your current dose is producing an appropriate amount of the drug in your body.

: Why Your Clinician May Order It

: Blood levels of quinidine can vary from person to person, and the right dose differs depending on how your body handles the drug. Your clinician may order this test to check that your dose is neither too low to control your rhythm nor too high to cause problems. It may also be checked if your dose changes, if you start or stop other medicines, or if you have kidney or liver conditions that affect drug levels.

: How the Sample Is Collected

: A small blood sample is drawn from a vein, usually in your arm, and sent to the laboratory. The exact time of collection can matter because drug levels rise and fall after each dose, so follow any instructions your clinician gives you about when to have the blood drawn relative to your last dose.

: What to Tell Your Care Team

: Let your clinician know all prescription and over-the-counter medicines and supplements you take, because some can change quinidine levels. Also mention any kidney or liver problems, changes in your heart symptoms, and any side effects such as dizziness, nausea, or palpitations, as these details help interpret the result.