Nortriptyline also known as Avntyl sold under Pamelor is a kind of antidepressant that is used to treat depression, ADHD, neuropathic pain, anxiety and ADHD. This is a derivative of amitriptyline that is used to treat bipolar disorder. The test measures the level of this drug in plasma that gives an indication of its effectiveness and patients’ response to the same.

How the Test Is Done

A sample of blood is collected with 1 ml. of serum or plasma to be clinically tested in the lab. This is transferred to a plastic transport tube. One should always take care that it should not be a gel barrier tube as the gel can slowly absorb the drug leading to false report. Based on the volume of specimen and storage time, there may be significant decrease in drug level.

How the test result is interpreted

If concentration of the drug in plasma is less than 50 ng/mL that is considered ineffective in response.

If it is greater than 150−175 ng/mL then this would indicate suboptimal response in patients with major depression. It has been found that excessive dosage diminish responsiveness.

In elderly patients, if the plasma nortriptyline concentrations is <150 ng/mL then also toxic side effects may develop.

Turnaround time

The turnaround time for the test is 2-5 days that means that the test report can only be availed within 2 days of providing the sample for the test.

Pregnant and lactating women are not considered suitable to be prescribed tricyclic antidepressant. These drugs may also cause urinary retention, postural problems in geriatric patients. Monitoring of therapeutic drugs helps doctors find out the efficacy of anti-depressants that also take into account other factors such as diet, co-medications, smoking habit, impaired organ function, and compliance.