Valproic acid is an antiepileptic drug that is usually used in the prevention of various types of seizures, although it can also be used for several other alternative indications.
Image Credit: Imageforge / Shutterstock.com
In the body, valproic acid 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.
Pharmacology
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.
Indications
The most widespread use of valproic acid is in the prevention of various types of epileptic seizures, including generalized, focal, and absence seizures. Valproic acid is also commonly used 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 attention deficit hyperactivity disorder (ADHD) and the prevention of migraines. However, sound scientific research to support its indication for these conditions is lacking and should therefore 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 associated with this drug is nausea and related gastrointestinal symptoms, although almost every organ and system of the body can 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 recognized by distinctive signs of an allergic reaction, such as swelling. In this case, further doses should be ceased and immediate medical attention should be sought if required.
Interactions
When valproic acid is administered together with other medications, there are several possible drug interactions that may occur.
Several drugs often used in the treatment of epilepsy alongside valproate include carbamazepine, phenobarbital, primidone, and phenytoin. These are known as metabolism enzyme inducers and increase the metabolism of valproate, which will reduce the efficacy of the current valproate dose and thus require more of the drug to be taken in order to achieve the desired therapeutic response.
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, such as warfarin, are being taken by the patient.
References
Further Reading