TRC: Valproic acid

Valproic acid

Valproic acid has several anticonvulsant properties: Sodium channel blocker: valproic acid slows the rate of channel recovery from inactivation, but to a lesser extent than other agents of this class.

GABA potentiator: valproic acid increases the GABA content of the brain. It is an inhibitor of GABA degrading enzymes and it is a potentiator of the GABA-synthesising enzyme glutamic acid decarboxylase.

T-type Ca channel inhibitor: valproic acid is thought to have similar actions as ethosuximide, as it is used in patients whose absences are refractory to ethosuximide.

Valproic acid is indicated for all forms of epilepsy. It also causes concentration-dependent adverse effects (AEs) which begin with tremor and GI effects, progress to ataxia, nystagmus, diplopia and at high concentrations cognitive changes and an altered level of consciousness. Chronic AEs include weight gain, idiosyncratic AEs include serious hepatotoxicity, blood dyscrasias, and rash.

Valproic acid has many interactions: it inhibits drug metabolism of other drugs.

Valproic acid is a first line drug in the following type of epilepsy

Extra info: Valproic acid is a useful drug in most types of epilepsy, with no specific age limit.

Option explanation:

tonic-clonic seizures

partial seizures

partial seizures with secondary generalisation

all the above

Women on valproic acid who are planning a baby should

Extra info: 5mg of folic acid in the first trimester is recommended for women with epilepsy because of the increased risk of neural tube defects. Valproic acid is a folate antagonist. Even in the first trimester, valproic acid should not be stopped suddenly, as there is no evidence for this reducing negative outcomes at this stage and the risk of a seizure outweighs any benefit. Valproic acid is shown to be teratogenic and should be replaced by lamotrigine or carbamazepine in order to reduce birth defects. Taking vita

Option explanation:

take 400mcg of folic acid throughout pregnancy

stop their valproic acid if they find they are pregnant unexpectedly

taper valproic acid and be changed to another antiepileptic drug

take oral vitamin K in the last month of pregnancy

Which monitoring is appropriate for a patient on valproic acid?

Extra info: Liver function tests should be performed before and during the first 6 months of use, particularly in high risk groups on valproic acid therapy. Patients should be taught to look for signs of blood dyscrasias, liver toxicity and pancreatitis.

Valproic acid

Valproic acid

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