Monitoring sodium valproate levels

The routine checking of serum sodium valproate levels is not generally supported (1,2).

If sodium valproate levels are indicated e.g. side effects, overdose then consider:

• usually is absorbed rapidly from the GI tract - peak serum concentrations are recorded from 1-8 hours
• therapeutic range: 50-100 mg/L (SI 350-690 mmol/L); however control of symptoms may be improved at levels higher than 100 mg/L (SI 690 mmol/L)
• toxic range:
  • mild symptoms - these may occur with levels higher than 100 mg/L (SI 690 mmol/L)
  • serious or fatal valproate intoxication is likely at levels higher than 800-1000 mg/L

NICE suggest that with respect to monitoring valproate (3):

• do not routinely measure plasma valproate evels unless there is evidence of ineffectiveness, poor adherence or toxicity
• measure the person's weight or BMI and carry out liver function tests and a full blood count again after 6 months of treatment with valproate and repeat annually
• monitor sedation, tremor and gait disturbance carefully in older people

Note that reference ranges may vary between laboratories and the local laboratory should be consulted regarding timing and assessment of levels.

Reference:

1. Thapar A et al. Are serum anticonvulsant levels in people with epilepsy appropriately monitored? J Eval Clin Pract. 2001 Aug;7(3):335-8.
2. French J. The long-term therapeutic management of epilepsy. Annals of Internal Medicine 1994; 120, 411-422.
3. NICE (April 2018). Bipolar disorder.