By Yolanda Smith, BPharm
Valproic acid is an antiepileptic drug that is usually used in the prevention of various types of seizure, although it can also be used for several other alternative indications.
In the body, it undergoes a reaction to become valproate ions, which are responsible for the pharmacological effects of the drug. In addition to the useful qualities of valproate, it can also result in a large number of side effects and has the potential to interact with several other drugs.
Valproate is thought to act via a number of mechanisms to produce the desired effect, which explains why it can be utilized for various different indications and seizure types associated with different pathways.
The primary mechanism of action involves an increase in the neurotransmitter gamma-aminobutyric acid (GABA) in the brain. Although it is not certain how this increase occurs, many medical researchers believe this may arise as a result of increased production or enhanced effect of the neurotransmitter.
Additionally, a secondary mechanism of action of valproate involves the inhibition of sodium and calcium channels in the brain, which also affects the propagation of seizures.
The most widespread use of valproic acid is in the prevention of various types of epileptic seizures, including generalized, focal and absence seizures. It is also commonly indicated to treat the manic episodes associated with bipolar disorder, in conjunction with other medications designed to target depressive symptoms.
Other uses of valproic acid include the treatment of neuropathic pain, aggression associated with ADHD and the prevention of migraines. However, sound scientific research to support its indication for these conditions is lacking and it should only be considered when other options with some evidence are disregarded.
Adverse Effects and Complications
Valproic acid has many possible side effects, due to the broad effect it has on the function of the brain and the rest of the body. The most common side effect is nausea and related gastrointestinal symptoms, although almost every organ and system of the body made be affected.
In addition to the adverse effects of valproic acid, there are more severe effects that can pose significant issues for some users.
Of particular note, pregnant women taking this medication are more likely to give birth to a child with congenital birth defects. As a result, most women taking valproate who are pregnant or planning to become pregnant should use an alternative medication. Additionally, all sexually active women of childbearing age should use adequate contraceptive protection to reduce the risk of an unplanned pregnancy.
Valproic acid may also cause significant damage to the liver or pancreas, which can be fatal in some cases. Signs of these complications, such a significant abdominal pain, nausea and vomiting, should be investigated further to determine the cause.
Some patients may also be allergic to valproic acid and experience a hypersensitivity reaction. This usually occurs shortly after initiation of therapy and is easily recognised by distinctive signs of allergy, such as swelling. In this case, further doses should be ceased and immediate medical attention if required.
When valproic acid is administered together with other medications, there are several possible drug interaction that may occur.
Several drugs often used in the treatment of epilepsy alongside valproate are carbamazepine, phenobarbital, primidone and phenytoin. These are known as metabolism enzyme inducers and increase the metabolism of valproate, leading to a required increase in dose.
Additionally, valproate can affect the bleeding time of a patient when a small blood injury occurs. This can be particularly problematic when anticoagulant medications that alter bleeding time precisely such as warfarin are being used by the patient.
Last Updated: Jul 20, 2015