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Alternative names
Flecainide - serum; Digoxin - serum; Ethosuximide - serum; Disopyramide - serum; Digitoxin - serum; Lidocaine - serum; Kanamycin - serum; Gentamicin - serum; Imipramine - serum; Lithium - serum; Amikacin - serum; Acetaminophen - serum; Aminophylline - serum; TDM; Desipramine - serum; Chloramphenicol - serum; Amitriptyline - serum; Carbamazepine - serum; Methotrexate - serum; Therapeutic drug monitoring; Theophylline - serum; Tobramycin - serum; Valproic acid - serum; Quinidine - serum; Serum drug levels; Salicylate - serum; Propranolol - serum; Phenytoin - serum; Phenobarbital - serum; Procainamide - serum; Primidone - serum; Nortriptyline - serumDefinition Return to top
Therapeutic drug level tests are usually performed to look for the presence and the amount of specific drugs in the blood.How the test is performed Return to top
Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band is placed around the upper arm to cause the vein to swell with blood.
A needle is inserted into the vein, and the blood is collected in air-tight vials or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
Infant or young child:
The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.
The sample is then taken to the laboratory, where it is evaluated for the particular drug specified by your health care provider.
How to prepare for the test Return to top
Some drug level tests require preparation. Ask your health care provider for preparation information related to the test ordered.How the test will feel Return to top
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.Why the test is performed Return to top
Testing involves taking multiple measurements of blood levels of a drug over time. The main purpose is to determine the effective drug dosages and to prevent toxicity. Drug level testing is especially important in people taking drugs such as:
Often, these are drugs where the margin of safety between therapeutic levels and toxic levels is narrow. Testing may also be done to determine absorption, rate of metabolism, or interaction with other necessary drugs.
Normal Values Return to top
Following are some of the drugs that are commonly checked, and their therapeutic levels:What abnormal results mean Return to top
Following are some of the drugs that are commonly checked, and their toxic levels:What the risks are Return to top
Risks associated with venipuncture are slight:Special considerations Return to top
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others. Update Date: 11/3/2003 Updated by: Sherry Woodhouse, M.D., Department of Pathology and Laboratory Medicine, Cleveland Clinic Florida, Weston, FL. Review provided by VeriMed Healthcare Network.
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Page last updated: 28 October 2004 |