From the Guidelines
The half-life of Valproic acid is approximately 7-13 hours in children less than 2 months old and 3.5-20 hours in children 2-14 years old. When considering the half-life of Valproic acid, it's essential to take into account the age of the patient, as it significantly affects the drug's metabolism.
- In children under 2 months, the half-life ranges from 7-13 hours 1.
- In children between 2-14 years, the mean half-life is around 9 hours, with a range of 3.5-20 hours 1. It's crucial to note that these values are based on the study published in Pediatrics in 2011 1, which provides the most recent and relevant information on the half-life of Valproic acid in pediatric patients. The half-life of Valproic acid is an important factor in determining the appropriate dosing interval and in interpreting blood level measurements for therapeutic drug monitoring.
- Physicians should be aware that organ dysfunction and hypothermia can affect the metabolism of pharmacologic agents, including Valproic acid 1.
- Additionally, the total amount of administered medication can impact drug metabolism and levels, emphasizing the need for careful monitoring and dose adjustment as necessary 1.
From the FDA Drug Label
Mean terminal half-life for valproate monotherapy ranged from 9 to 16 hours following oral dosing regimens of 250 to 1000 mg.
The half-life of Valproic acid is 9 to 16 hours for monotherapy, following oral dosing regimens of 250 to 1000 mg 2.
- This range applies primarily to patients who are not taking drugs that affect hepatic metabolizing enzyme systems.
- The half-life may be affected by various factors, including age, liver disease, and renal disease.
From the Research
Half-Life of Valproic Acid
The half-life of valproic acid varies depending on several factors, including age and formulation.
- In adults, the half-life of valproic acid ranges from 10 to 20 hours 3.
- In children, the half-life is significantly shorter, ranging from 6 to 9 hours 3.
- The elimination half-life of valproic acid can also vary depending on the population, with a range of 4-16 hours in different populations (children vs adults, enzyme-induced vs uninduced) 4.
- A study in adolescents and young adults found that the terminal half-life of free valproic acid was 6.4-6.7 hours, which is significantly shorter than the half-life of total valproic acid (10.4-11.9 hours) 5.
- In the elderly, the half-life of valproic acid is similar to that in young adults, with a range of 13-15 hours 6.
Factors Affecting Half-Life
Several factors can affect the half-life of valproic acid, including:
- Age: Children have a shorter half-life than adults 3.
- Formulation: Different formulations of valproic acid can have different absorption half-lives, ranging from less than 30 minutes to 3 or 4 hours 3.
- Enzyme induction: Enzyme induction can decrease the half-life of valproic acid 4.
- Plasma protein binding: The binding of valproic acid to plasma proteins can affect its half-life, with free valproic acid having a shorter half-life than total valproic acid 5, 6.