Trazodone: Pharmacokinetics & Mechanism of Action

Instructor: Justine Fritzel

Justine has been a Registered Nurse for 10 years and has a Bachelor's of Science in Nursing degree.

What is trazodone and what is it used for? In this lesson, we will learn about trazodone use. We will also look at the pharmacology of trazodone, specifically the pharmacokinetics and mechanism of action.


Mary has been feeling down a lot lately. She doesn't have the motivation to do anything, even things she used to enjoy. She has been eating more and has gained 5lbs in the last month. Some days she literally can't even get out of bed. But then at night, she can't sleep. She goes to see her doctor and he tells her she is experiencing depression. He prescribes her a drug called trazodone. He tells her to take it at night so it can also help with her insomnia.

Trazodone is an oral medication that is used for depression. It can also be used to treat anxiety and chronic pain. It has a secondary effect to help with insomnia so it can be beneficial to take at night.

Let's learn more about trazodone by looking at pharmacokinetics and mechanism of action.


Pharmacokinetics is how a drug moves through the body. This includes absorption, metabolism, and excretion.

Absorption is how the drug is absorbed in the body. Trazodone is absorbed after oral administration. It is recommended to take on an empty stomach because taking it with food can affect the levels of the drug in the body.

Metabolism is a wide range of processes within the body that either builds up or breaks down different substances. Trazodone is metabolized by the liver and is changed into an active metabolite. An active metabolite just refers to the active form of the drug after it has been metabolized, this is what makes it work! It is changed to m-chlorophenylpiperazine (mCPP) by cytochrome P450 3A4 (CYP3A4). Whoa, that was technical! Think of the liver as Superman's phone booth. Clark Kent goes into the phone booth and comes out as Superman in the same way that trazodone is metabolized in the liver to the active metabolite.

Half-life refers to the amount of time it takes for the amount of the drug in the body to decrease by half. The half-life of trazodone is 3-6 hours in the first phase and then 5-9 hours in the second phase. This is the process of how the drug leaves the body, or excretion. Trazodone is excreted mainly in the urine.

So how exactly does trazodone work?

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