Nichelle asked
Hello. Can someone clarify a question about Ambien. I have a client who was taking 10mg for a few years before bed for insomnia. She took a blood test 16+ hours after she took the Ambien and the test came back with 145ng/mL. Is this normal?
Answer
Laboratory monitoring or blood testing of Ambien (zolpidem) generally isn't necessary or recommended to asses therapeutic effect. As such, there is as distinct lack of information in regard to what "normal" blood levels of Ambien are. Nevertheless, there have been a few studies that we discuss below.
"Normal" Ambien (Zolpidem) Blood Levels
According to the prescribing information for Ambien, blood concentrations for Ambien are as follows:
- After administration of 5 and 10 mg zolpidem tablets, average peak concentrations were 59 ng/mL (range: 29 to 113) and 121 ng/mL (range: 58 to 272), occurring at an average time of 1.6 hours after dosing for both.
Our bodies metabolize Ambien quickly, with a reported half-life (time it takes to metabolize 50% of a drug) of only 2-3 hours. Therefore, most single doses are Ambien are metabolized and eliminated from the body within 24 hours. However, there are several factors that can greatly prolong the half-life of Ambien in individuals, such as age, dosing history and liver impairment.
Factors That Influence Ambien (Zolpidem) Metabolism
Studies show that liver impairment can extend to the half-life of Ambien to over 10 hours, nearly 5 times the average range for non-liver impaired individuals. In addition, the half-life is increased in the elderly and in females.
Multiple studies that evaluate blood levels of Ambien (such as in studies that investigate impaired driving) state that average blood concentrations are around 30-100 ng/mL in those who take the drug consistently, with higher concentrations (e.g. >100 ng/mL) being associated with impaired driving. Acute overdose blood levels of Ambien are generally over 1,000 ng/ml according to studies evaluating such cases.
As the individual in question has been taking Ambien consistently for years, blood concentrations have almost assuredly reached a steady state level, where blood levels (technically the AUC, or area under the curve) of the drug will stay relatively consistent on a daily basis.
According to all the published data, 145 ng/mL appears to be an acceptable and common range, when taking into account single dose concentrations of Ambien 10 mg can produce blood levels over 270 ng/mL, individuals taking the drug consistently for long period of time will reach a steady state concentration and the half-life can be greatly extended in those with certain characteristics (e.g. age, liver impairment).
If the individual referred to in this inquiry is feeling residual daily effects of Ambien, they should be sure to see their doctor to be evaluated.
