Tricyclic antidepressant (TCA) testing
This test is used to check a sample of blood or urine for tricyclic antidepressants (TCAs). Health care providers prescribe these drugs for depression and a number of other problems, including anxiety, headaches, and nerve-related pain.
Although these drugs can be helpful in normal doses, taking too much can be fatal. These drugs are often the cause of death in prescription-drug overdoses in the U.S.
You might have this test to help your health care provider prescribe the proper dose of TCA. Health care providers may also perform this test if you have symptoms that may point to taking too much of one of these drugs.
Symptoms of overdose include:
Serious changes in heart rhythm
Low blood pressure
If your health care provider suspects that you have taken too much of one of these drugs, he or she may perform an electrocardiogram to check your heart's rhythm. Your doctor may also perform other blood tests, including a complete blood count; creatinine; electrolytes; blood sugar; and to check for other substances including acetaminophen and aspirin, which are other drugs that are commonly taken along with a TCA overdose.
A result for a lab test may be affected by many things, including the method the laboratory uses to do the test. If your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.
Blood levels higher than 1,000 nanograms per milliliter (ng/mL) can threaten your life. Even much lower levels may be harmful, especially in children and people taking these drugs long-term. Levels higher than 3,000 ng/mL often cause death.
The test requires a blood sample, which is drawn through a needle from a vein in your arm, or a urine sample, which is usually provided by urinating into a cup. The result of a urine test for TCAs will be reported only as negative or positive.
Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.
Some other medications can interfere with this test, causing a false-positive for TCAs. These include carbamazepine, quetiapine, diphenhydramine, thioridazine, chlorpromazine, and cyclobenzaprine.
Tell your health care provider about any other medications you have taken recently.