How Long Does Ambien (Zolpidem) Stay In Your System?

Mieke asked

I took 2 Ambien (zolpidem) 10 mg yesterday at 4 PM. I had a screening at 10 this morning. I'm afraid I will test positive. What do you think?

Answer

How long Ambien (zolpidem) stays in your system, and the detection time for it on a drug test, can vary considerably by the individual.

Reported detection times range from 12 to 72 hours! Below, we discuss zolpidem metabolism and why there is such a wide range of time it can stay in your body.

Drug-Half Life Confusion

One of the more common measures of how long a drug lasts in your system is the 'half-life'. The elimination half-life of a drug is the time it takes for the body to metabolize and eliminate 50% of it from the blood. In general, it takes around five to six half-lives for a drug to be considered completely metabolized from the body and no longer detectable on a drug test.

The half-life of Ambien (technically zolpidem as it is the active ingredient) is around 2 to 3 hours. Therefore, you would expect Ambien to be completely eliminated in 10 to 15 hours. This, however, is not the case for many individuals based on published reports. One study reported that Ambien was detectable in the urine for up to 60 hours (3). Per the study:

"Zolpidem was detected for up to 60 h in urine with peak concentrations obtained at 12 h."

Another study reported that zolpidem is detectable for up to 72 hours!

The half-life of Ambien alone clearly isn't the only factor that determines how long it lasts in the body.

In fact, it is important to note that when referring to the 'half-life' of a drug, typically, this is in reference to the elimination half-life in the plasma (i.e. blood). Drugs that have extensive tissue absorption can stay in the body for long periods of time, well past the published half-life (one good example is cannabis).

Variables That Affect Ambien Elimination

It is well known that a variety of factors determine how quickly drugs are eliminated from the body, including:

• Drug-protein binding
• Volume of distribution
• Age
• Tissue penetration
• Gender
• Kidney/liver function
• Active metabolites

Aside from half-life, the important variables determining Ambien elimination are most likely liver function, active metabolites, age, and protein binding.

Liver Dysfunction And Ambien Metabolism 

Ambien elimination is greatly altered with changes in liver function. For example, in patients with cirrhosis, studies show that the half-life can be significantly increased to an average of 9.9 hours (ranging from 4.1 to 25.8 hours).

If your liver function is reduced, elimination rates for Ambien will greatly increase. Based on the prolonged half-life numbers (4.1-25.8 hours), this means it could theoretically stay in your system for more than 5 days!

In addition, Ambien is extensively metabolized in the liver by a variety of enzymes.

Drug interactions that inhibit certain liver metabolizing enzymes (such as CYP3A4) could potentially prolong how long the drug lasts in the body. For example, when Ambien was given with ketoconazole, a potent CYP3A4 inhibitor, the elimination half-life increased by approximately 30%.

Active Metabolites

Very often, a published half-life refers only to the 'parent' compound of a drug, in this case 'zolpidem'. However, many drugs have metabolites which are by-products of metabolism. When it comes to drug tests, many actually look for metabolites of the parent compound, as opposed to the parent compound itself, since they last much longer in the body.

Most drugs tests don't look for 'zolpidem' but rather the metabolite 'zolpidem 4-phenyl carboxylic acid' (ZCA). Based on the data available, it appears to be the metabolite that lasts for extended time periods in your system. This active metabolite is the most likely reason why 'Ambien' is detectable longer than the half-life would indicate.

Age

Ambien is metabolized slower in older individuals. It is been reported that the average half-life increases on average by 3 hours in elderly individuals.

Protein Binding

While protein binding probably isn't a huge factor in Ambien elimination time, it is still worth noting.

Ambien is highly protein-bound in the blood (~92%). Any change in protein binding can significantly affect characteristics like drug elimination. 

 Many factors can affect the extent of protein binding, including:

• Kidney/liver function
• Stress
• Concomitant medication
• Concomitant disease states (e.g. hyperalbuminemia)

There isn't much data on protein binding and associated elimination rates when it comes to Ambien and it most likely isn't a huge factor.

Final Words

It can't be emphasized enough that the published half-life of a drug is but one indicator of how long it will last in the body. This is very evident with Ambien as it has a published half-life of 2 to 3 hours, but studies indicate that it can be detectable for days. This is most likely due to a variety of factors, including:

• Protein binding
• Metabolites
• Age
• Liver function/Drug interactions

To recap, based on the half-life of Ambien, the majority of the drug will be eliminated in 12-14 hours for most individuals. However, studies report that Ambien can stay in your system for up to 72 hours based on a variety of factors (e.g. test looking for metabolites, liver function, etc...).

As a final note, although a drug test that involves the collection of hair would be uncommon for Ambien, it has been reported that it will be detectable for up to 5 weeks in hair follicles.