Tricyclic Antidepressant Screen

Tricyclic antidepressant (TCA) testing

This test is used to check a sample of blood or urine for tricyclic antidepressants (TCAs). Healthcare providers prescribe these medicines for depression and a number of other problems. These include anxiety, headaches, and nerve-related pain.

These medicines can be helpful in normal doses. But taking too much can be fatal. These medicines are often the cause of death in prescription-medicine overdoses in the U.S. 

You may need this test to help your healthcare provider prescribe the proper dose of a TCA. Healthcare providers may also do this test if you have symptoms that may point to taking too much of one of these medicines.

Symptoms of overdose include:

• Sedation

• Trouble thinking

• Confusion

• Hallucinations

• Serious changes in heart rhythm

• Low blood pressure

• Seizures

• Body temperature that is too high (hyperthermia)

• Dry mouth

• Dilated pupils

If your healthcare provider suspects that you have taken too much of one of these medicines, an electrocardiogram is often done to check your heart's rhythm. Your provider may also order other blood tests. These include a complete blood count (CBC), creatinine, electrolytes, and blood sugar. Your provider will also check for other substances that are commonly taken along with a TCA overdose. 

Test results may vary depending on your age, gender, health history, and other things. Your test results may be different depending on the lab used. They may not mean you have a problem. Ask your healthcare provider what your test results mean for you.

Depending on the tricyclic antidepressant medicine you are taking, the level for treatment will vary.

The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand. Or it is done with 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.

Having a blood test with a needle carries some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore. 

Some other medicines can interfere with this test, causing a false-positive for TCAs. These include carbamazepine, quetiapine, diphenhydramine, and cyclobenzaprine.

Be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use.