How Long Is Valium (Diazepam) Detectable In Your System?

In our latest question and answer, the pharmacist discusses how long Valium (diazepam) is detectable in your system.

Mar 16, 2018

Jae asked

How’s long is Valium detectable in the system?

Answer

Valium (diazepam) is a benzodiazepine medication that is noted for its long half-life when compared to other medications in the class. Due to the long half-life of the drug, data indicates that Valium is detectable in your system (i.e. on a drug test) for up to 30 days.

Valium Half-Life

Half-life refers to the time it takes for 50% of a drug to be metabolized and eliminated from the body. Therefore, drugs with a long half-life tend to be detectable on standard urine drug tests for a longer period of time than drugs with a short half-life.

The active ingredient in Valium, diazepam, has a half-life of around 48 hours while one of its metabolites (i.e. metabolism by-product),  N-desmethyldiazepam, has a half life of nearly 100 hours. In addition, diazepam can accumulate in the body after prolonged and consistent dosing, which may prolong the half-life even further.

Diazepam, and its metabolites are excreted mainly in the urine, making standard urine drug tests a popular option for testing.

Most employers and medical offices use a simple, urine based immunoassay tests known as an EIA (Enzyme Linked Immunoassay) test. Immunoassay tests work by utilizing antibodies to react to specific drug compounds. A positive result will occur, when a specified drug is present in a test urine sample and an antibody binds to it. This produces a reaction which is recorded as a positive result.

How Long Is Valium Detectable?

Most immunoassay urine tests designed to detect N-desmethyldiazepam (also known as nordiazepam), not the parent compound (diazepam) according to studies. Therefore, to determine how long diazepam is detectable in your system (i.e. a drug test), you need to considered N-desmethyldiazepam, which has an extremely long half life.

Most sources state that N-desmethyldiazepam, the metabolite being tested for, will be detectable in your system on urine tests for up to 30 days. When we consider the 100 hour half life, this makes sense.

A general rule of thumb is that it takes around 5 half-lives for a drug to no longer be detectable in your system, which translates to 500 hours, or around 21 days for the diazepam metabolite N-desmethyldiazepam. Considering that diazepam can accumulate in the system, prolonging the half life, up to 30 days is a good estimate for how long it lasts in your system.

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