From the Guidelines
Valium (diazepam) has a half-life ranging from 15-95 hours, depending on the age of the patient, with infants having the longest half-life. The half-life of Valium varies significantly across different age groups, with infants (1 month–2 years) having a half-life of 40–50 hours, children (2 years–12 years) having a half-life of 15–21 hours, and adolescents (12–16 years) having a half-life of 18–20 hours 1. This information is crucial for clinicians to consider when prescribing Valium, as its prolonged half-life can lead to accumulation and increased risk of adverse effects, particularly in younger patients or those with impaired liver function. Key factors that influence the half-life of Valium include age, liver function, and the presence of active metabolites, which can further prolong the drug's effects 1. It is essential to consider these factors when determining the timing of neurologic examinations, such as those for brain death, to ensure that the patient's condition is not influenced by the residual effects of Valium or its metabolites. In some cases, waiting several half-lives and rechecking serum levels of the medication may be necessary to confirm that the drug's levels are within a low to mid therapeutic range before conducting a brain death examination 1. Overall, understanding the half-life of Valium and its variations across different age groups is vital for safe and effective prescribing practices.
From the FDA Drug Label
The initial distribution phase has a half-life of approximately 1 hour, although it may range up to >3 hours. The terminal elimination half-life of diazepam is up to 48 hours The terminal elimination half-life of the active metabolite N-desmethyldiazepam is up to 100 hours Diazepam Half-Life:
- Initial distribution phase: approximately 1 hour (up to 3 hours)
- Terminal elimination phase: up to 48 hours
- Active metabolite N-desmethyldiazepam: up to 100 hours 2
From the Research
Valium Half-Life
- The half-life of Valium (diazepam) is affected by various factors, including age and liver disease 3.
- In elderly patients, the elimination half-life of diazepam is prolonged, with a mean half-life of 86 hours compared to 31 hours in young volunteers 4.
- The half-life of diazepam's active metabolite, desmethyldiazepam, is also prolonged in elderly patients, with a mean half-life of 80 hours compared to 40 hours in young volunteers 4.
- The effective duration of action of diazepam in status epilepticus is only 20 to 30 minutes due to its high lipid solubility and large volume of distribution of unbound drug 5.
- Diazepam's pharmacokinetic properties, including its half-life, can influence its clinical use and efficacy in various conditions, such as epilepsy and anxiety disorders 6, 7.