What is the half-life of Diazepam (Valium)?

From the Guidelines

The half-life of Valium (diazepam) is approximately 20-120 hours. This information is based on the clinical pharmacology of sedative medications outlined in a study published in Critical Care Medicine 1. The half-life of diazepam can vary significantly, and it is essential to consider factors such as age, liver function, and genetics when determining the duration of its effects. Some key points to consider about the half-life of Valium include:

• The extended half-life means that the drug stays in the system for a considerable time, with its active metabolites having half-lives of up to 120 hours.
• The half-life can vary significantly between individuals, with older adults and those with liver impairment typically experiencing longer half-lives due to decreased metabolism.
• This prolonged duration has clinical implications, including a lower risk of withdrawal symptoms between doses compared to shorter-acting benzodiazepines, but also means the drug can accumulate in the body with repeated dosing, potentially leading to increased sedation over time. The information provided in the study 1 highlights the importance of considering the pharmacokinetics of sedative medications, including diazepam, when managing patients in the intensive care unit.

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 In children 3 to 8 years old the mean half-life of diazepam has been reported to be 18 hours. In full term infants, elimination half-lives around 30 hours have been reported, with a longer average half-life of 54 hours reported in premature infants Elimination half-life increases by approximately 1 hour for each year of age beginning with a half-life of 20 hours at 20 years of age In mild and moderate cirrhosis, average half-life is increased, with individual half-lives over 500 hours reported

The half-life of Valium (diazepam) is up to 48 hours. However, it's essential to note that the half-life can vary depending on factors such as:

• Age: Half-life increases by approximately 1 hour for each year of age, starting with a half-life of 20 hours at 20 years of age.
• Population:
  • Children (3-8 years old): 18 hours
  • Full-term infants: around 30 hours
  • Premature infants: up to 54 hours
• Hepatic function: Half-life is increased in patients with mild and moderate cirrhosis, with individual half-lives over 500 hours reported 2

From the Research

Half-Life of Valium (Diazepam)

The half-life of Valium, also known as diazepam, varies depending on several factors such as age, liver function, and duration of treatment.

• The normal half-life of diazepam is between 1 and 2 days 3.
• However, in subjects over 60 years of age, the half-life can be increased to up to 80-100 hours 3.
• In patients with liver disease, the half-life is about doubled due to a reduction in hepatic clearance 3.
• The half-life of diazepam can also be affected by the duration of treatment, with subchronic treatment resulting in a reduced elimination rate in healthy subjects 3.
• A study found that the mean half-life of diazepam in elderly subjects was 86 hours, compared to 31 hours in young volunteers 4.
• The half-life of desmethyldiazepam, the active metabolite of diazepam, is around 51 hours 3 and can accumulate after multiple doses of diazepam.
• Another study found that the half-life of desmethyldiazepam in elderly subjects was 80 hours, compared to 40 hours in young volunteers 4.

Factors Affecting Half-Life

Several factors can affect the half-life of diazepam, including:

• Age: Elderly subjects tend to have a longer half-life of diazepam and its active metabolite 3, 4.
• Liver function: Patients with liver disease tend to have a longer half-life of diazepam due to reduced hepatic clearance 3, 5.
• Duration of treatment: Subchronic treatment with diazepam can result in a reduced elimination rate in healthy subjects 3.
• Metabolism: Diazepam is metabolized by hepatic oxidation and glucuronidation, and its metabolism can be affected by age and liver disease 5.