Valproate
Valproate (valproic acid, VPA, sodium valproate, and valproate semisodium forms) are medications primarily used to treat epilepsy and bipolar disorder and prevent migraine headaches. They are useful for the prevention of seizures in those with absence seizures, partial seizures, and generalized seizures. They can be given intravenously or by mouth, and the tablet forms exist in both long- and short-acting formulations.
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| Trade names | Depakote, Epilim, Convulex, others |
| Other names | Valproic acid; Sodium valproate (sodium); Valproate semisodium (semisodium); 2-Propylvaleric acid |
| AHFS/Drugs.com | Monograph |
| MedlinePlus | a682412 |
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| Routes of administration | By mouth, intravenous |
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| Bioavailability | Rapid absorption |
| Protein binding | 80–90% |
| Metabolism | Liver—glucuronide conjugation 30–50%, mitochondrial β-oxidation over 40% |
| Elimination half-life | 9–16 hours |
| Excretion | Urine (30–50%) |
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| ECHA InfoCard | 100.002.525 |
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| Formula | C8H16O2 |
| Molar mass | 144.214 g·mol−1 |
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Common side effects of valproate include nausea, vomiting, somnolence, and dry mouth. Serious side effects can include liver failure, and regular monitoring of liver function tests is therefore recommended. Other serious risks include pancreatitis and an increased suicide risk. Valproate is known to cause serious abnormalities in fetuses if taken during pregnancy, and is contra-indicated for women of childbearing age unless the drug is essential to their medical condition and the recipient is also prescribed a contraceptive. The United States FDA has indicated a black box warning given the frequency and severity of the side effects and teratogenicity. As of 2022 the drug was still prescribed in the UK to potentially pregnant women, but use declined by 51% from 2018–19 to 2020–21. Valproate's precise mechanism of action is unclear. Proposed mechanisms include affecting GABA levels, blocking voltage-gated sodium channels, inhibiting histone deacetylases, and increasing LEF1. Valproic acid is a branched short-chain fatty acid (SCFA), a derivative of valeric acid.
Valproate was first made in 1881 and came into medical use in 1962. It is on the World Health Organization's List of Essential Medicines and is available as a generic medication. In 2020, it was the 109th most commonly prescribed medication in the United States, with more than 6 million prescriptions.