OverviewDosageSide EffectsInteractionsHalf-Life

Mirtazapine was the 119th most commonly prescribed drug in the United States in 2017. In that year alone, there were over six million prescriptions issued. Considering how popular this drug is right now, it pays to know a little bit more about this medication, including how long mirtazapine stays in your system.

Basic Information

The FDA states the following information regarding mirtazapine half-life:

Mean effective half-life: 20 to 40 hours

Time to steady-state: Five days

Mean accumulation ratio: 1.5

Terminal phase half-life: 20 to 40 hours

Mirtazapine has an oral bioavailability of 50 percent. Once metabolized, elimination is completed via urine and feces. 


What is the half-life of mirtazapine?

20 to 40 hours.

How long does mirtazapine stay in your system?

Mirtazapine is detectable in your system for the following time frames:

Mirtazapine has a half-life of 20 to 40 hours. This means it will be in the body for up to eight days. Most of it leaves through the urine, so that is where detection is most likely. Blood, saliva, and hair tests for this medication are not likely.

How long does it take for mirtazapine to work for sleep?

Mirtazapine is sometimes used as a sleep medication. It can make a person drowsy and also increase the amount of time they stay asleep. It’s unclear how long it would take to be effective for this purpose, but most see some improvement within the first or second week of taking this drug. 

Does mirtazapine make you tired the next day?

Taking mirtazapine can lead to daytime sleepiness. 

Disclaimer: this article does not constitute or replace medical advice. If you have an emergency or a serious medical question, please contact a medical professional or call 911 immediately. To see our full medical disclaimer, visit our Terms of Use page.

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