Valproate

Contraindications

Contraindications include:

• Pre-existing acute or chronic liver dysfunction or family history of severe liver inflammation (hepatitis), particularly medicine related.
• Pregnancy 11% risk of birth defects and 30-40% risk of neuro-developmental disabilities which can be permanent
• Known hypersensitivity to valproate or any of the ingredients used in the preparation
• Urea cycle disorders
• Hepatic porphyria
• Hepatotoxicity
• Mitochondrial disease
• Pancreatitis
• Porphyria

Adverse effects

Most common adverse effects include:

• Nausea (22%)
• Drowsiness (19%)
• Dizziness (12%)
• Vomiting (12%)
• Weakness (10%)

Serious adverse effects include:

• Bleeding
• Low blood platelets
• Encephalopathy
• Suicidal behavior and thoughts
• Low body temperature

Valproic acid has a black box warning for hepatotoxicity, pancreatitis, and fetal abnormalities.

There is evidence that valproic acid may cause premature growth plate ossification in children and adolescents, resulting in decreased height. Valproic acid can also cause mydriasis, a dilation of the pupils. There is evidence that shows valproic acid may increase the chance of Polyendocrine metabolic ovarian syndrome (PMOS) in women with epilepsy or bipolar disorder. Studies have shown this risk of PMOS is higher in women with epilepsy compared to those with bipolar disorder. Weight gain is also possible. Valproic acid may decrease platelets in proportion to its dosage, particularly in women and the elderly.

Pregnancy

Fetal valproate spectrum disorder (FVSD), previously known as fetal valproate syndrome (FVS), is a rare disease caused by prenatal exposure to valproic acid (VPA), a medication commonly used to treat epilepsy, bipolar disorder, and migraines. This exposure can lead to a range of neurodevelopmental and physical symptoms, including cognitive impairments, developmental delays, autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), and congenital malformations.

Valproate is a teratogen. Teratogens can cause birth defects. Valproate is restricted for all women under age 55 in the United Kingdom and European Union. It has a black box warning for pregnancy in the United States.

There are also restrictions for men. Children fathered by men taking valproate have a higher risk of neurodevelopmental disorders. Valproate is restricted for men under age 55 in the United Kingdom and European Union. The restrictions require two specialists to agree that there is no other effective or tolerated treatment for the patient.

Elderly

Valproate may cause increased somnolence in the elderly. In a trial of valproate in elderly patients with dementia, a significantly higher portion of valproate patients had somnolence compared to placebo. In approximately one-half of such patients, there was associated reduced nutritional intake and weight loss.

Overdose

Excessive amounts of valproic acid can result in somnolence, tremor, stupor, respiratory depression, coma, metabolic acidosis, and death. In general, serum or plasma valproic acid concentrations are in a range of 20–100 mg/L during controlled therapy, but may reach 150–1500 mg/L following acute poisoning. Monitoring of the serum level is often accomplished using commercial immunoassay techniques, although some laboratories employ gas or liquid chromatography. In contrast to other antiepileptic drugs, at present there is little favorable evidence for salivary therapeutic drug monitoring. Salivary levels of valproic acid correlate poorly with serum levels, partly due to valproate's weak acid property (pKa of 4.9).

In severe intoxication, hemoperfusion or hemofiltration can be an effective means of hastening elimination of the drug from the body. Supportive therapy should be given to all patients experiencing an overdose and urine output should be monitored. Supplemental L-carnitine is indicated in patients having an acute overdose and also prophylactically in high risk patients. Acetyl-L-carnitine lowers hyperammonemia less markedly than L-carnitine.

Interactions

Valproate inhibits CYP2C9, glucuronyl transferase, and epoxide hydrolase and is highly protein bound and hence may interact with drugs that are substrates for any of these enzymes or are highly protein bound themselves. It may also potentiate the CNS depressant effects of alcohol. It should not be given in conjunction with other antiepileptics due to the potential for reduced clearance of other antiepileptics (including carbamazepine, lamotrigine, phenytoin and phenobarbital) and itself. It may also interact with:

• Aspirin: may increase valproate concentrations. May also interfere with valproate's metabolism.
• Benzodiazepines: may cause CNS depression and there are possible pharmacokinetic interactions.
• Carbapenem antibiotics: reduce valproate levels, potentially leading to seizures.
• Cimetidine: inhibits valproate's metabolism in the liver, leading to increased valproate concentrations.
• Erythromycin: inhibits valproate's metabolism in the liver, leading to increased valproate concentrations.
• Ethosuximide: valproate may increase ethosuximide concentrations and lead to toxicity.
• Felbamate: may increase plasma concentrations of valproate.
• Mefloquine: may increase valproate metabolism combined with the direct epileptogenic effects of mefloquine.
• Oral contraceptives: may reduce plasma concentrations of valproate.
• Primidone: may accelerate metabolism of valproate, leading to a decline of serum levels and potential breakthrough seizure.
• Rifampicin: increases the clearance of valproate, leading to decreased valproate concentrations.
• Warfarin: valproate may increase free warfarin concentration and prolong bleeding time.
• Zidovudine: valproate may increase zidovudine serum concentration and lead to toxicity.

Pharmacology

Pharmacodynamics

Although the mechanism of action of valproate is not fully understood, traditionally, its anticonvulsant effect has been attributed to the blockade of voltage-gated sodium channels and increased brain levels of the inhibitory synaptic neurotransmitter gamma-aminobutyric acid (GABA). The GABAergic effect is also believed to contribute towards the anti-manic properties of valproate. In animals, sodium valproate raises cerebral and cerebellar levels of GABA, possibly by inhibiting GABA degradative enzymes, such as GABA transaminase, succinate-semialdehyde dehydrogenase and by inhibiting the re-uptake of GABA by neuronal cells. Prevention of neurotransmitter-induced hyperexcitability of nerve cells via Kv7.2 channel and AKAP5 may also contribute to its mechanism. Valproate has been shown to protect against a seizure-induced reduction in phosphatidylinositol (3,4,5)-trisphosphate (PIP3) as a potential therapeutic mechanism.

Valproate is a weak or low-potency histone deacetylase inhibitor, specifically of the class I HDAC1, HDAC2, HDAC3, and HDAC8, but not of other HDACs. Earlier studies found a wide range of inhibitory potencies of valproate against HDACs, ranging from low micromolar to millimolar concentrations, but subsequent work with improved methodology has supported greater inhibitory potencies, with IC₅₀Tooltip half-maximal inhibitory concentration values in the range of 36 to 219 μM for the class I HDACs. For comparison, valproate was found to be 4- to 46-fold less potent in inhibiting the class I HDACs relative to butyric acid (butyrate). By inhibiting HDACs, valproate promotes more transcriptionally active chromatin structures, that is it exerts an epigenetic effect. This has been proven in mice: Valproic acid induced histone hyperacetylation had brain function effects on the next generation of mice through changes in sperm DNA methylation. Intermediate molecules include VEGF, BDNF, and GDNF.

Endocrine actions

Valproic acid has been found to be an antagonist of the androgen and progesterone receptors, and hence as a nonsteroidal antiandrogen and antiprogestogen, at concentrations much lower than therapeutic serum levels. In addition, the drug has been identified as a potent aromatase inhibitor, and suppresses estrogen concentrations. These actions are likely to be involved in the reproductive endocrine disturbances seen with valproic acid treatment.

Valproic acid has been found to directly stimulate androgen biosynthesis in the gonads via inhibition of histone deacetylases and has been associated with hyperandrogenism in women and increased 4-androstenedione levels in men. High rates of polycystic ovary syndrome and menstrual disorders have also been observed in women treated with valproic acid.

Pharmacokinetics

Taken by mouth, valproate is rapidly and virtually completely absorbed from the gut. When in the bloodstream, 80–90% of the substance are bound to plasma proteins, mainly albumin. Protein binding is saturable: it decreases with increasing valproate concentration, low albumin concentrations, the patient's age, additional use of other drugs such as aspirin, as well as liver and kidney impairment. Concentrations in the cerebrospinal fluid and in breast milk are 1 to 10% of blood plasma concentrations.

The vast majority of valproate metabolism occurs in the liver. Valproate is known to be metabolized by the cytochrome P450 enzymes CYP2A6, CYP2B6, CYP2C9, and CYP3A5. It is also known to be metabolized by the UDP-glucuronosyltransferase enzymes UGT1A3, UGT1A4, UGT1A6, UGT1A8, UGT1A9, UGT1A10, UGT2B7, and UGT2B15. Some of the known metabolites of valproate by these enzymes and uncharacterized enzymes include (see image):

• via glucuronidation (30–50%): valproic acid β-O-glucuronide
• via beta oxidation (>40%): 2E-ene-valproic acid, 2Z-ene-valproic acid, 3-hydroxyvalproic acid, 3-oxovalproic acid
• via omega oxidation: 5-hydroxyvalproic acid, 2-propyl-glutaric acid
• some others: 3E-ene-valproic acid, 3Z-ene-valproic acid, 4-ene-valproic acid, 4-hydroxyvalproic acid

All in all, over 20 metabolites are known.

In adult patients taking valproate alone, 30–50% of an administered dose is excreted in urine as the glucuronide conjugate. The other major pathway in the metabolism of valproate is mitochondrial beta oxidation, which typically accounts for over 40% of an administered dose. Typically, less than 20% of an administered dose is eliminated by other oxidative mechanisms. Less than 3% of an administered dose of valproate is excreted unchanged (i.e., as valproate) in urine. Only a small amount is excreted via the faeces. Elimination half-life is 16±3 hours and can decrease to 4–9 hours when combined with enzyme inducers.

Chemistry

Valproic acid is a branched short-chain fatty acid (SCFA) and the 2-n-propyl derivative of valeric acid (valerate; pentanoic acid; pentanoate). It is also a GABA analogue, or analogue of the inhibitory neurotransmitter γ-aminobutyric acid (GABA). Other analogues of valproic acid include valproate pivoxil, valpromide, and valnoctamide.

History

Valproic acid was first synthesized in 1882 by Beverly S. Burton as an analogue of valeric acid, found naturally in valerian. Valproic acid is a carboxylic acid, a clear liquid at room temperature. For many decades, its only use was in laboratories as a "metabolically inert" solvent for organic compounds. In 1962, the French researcher Pierre Eymard serendipitously discovered the anticonvulsant properties of valproic acid while using it as a vehicle for a number of other compounds that were being screened for antiseizure activity. He found it prevented pentylenetetrazol-induced convulsions in laboratory rats. It was approved as an antiepileptic drug in 1967 in France and has become the most widely prescribed antiepileptic drug worldwide. Valproic acid has also been used for migraine prophylaxis and bipolar disorder.

Society and culture

Valproate is available as a generic medication.

Restrictions

In 2024, for those under age 55, additional restrictions for valproate prescription have been imposed in the United Kingdom. Patients under 55 can still receive valproate, but need to obtain the permission of two specialists. The restrictions are, in women, due to the potential for birth defects in children born of women of childbearing age. In men, the restrictions are due to the potential for reversible male infertility, testicular problems, and the risks of neurodevelopmental conditions in children born to men taking valproate in the 3 months before conception. Similar restrictions have been imposed in the European Union for both women and men. In February 2026, a French man, Jean-Marc Laurent, filed what has been described as the first legal complaint related to paternal exposure to valproate, alleging that his child developed neurodevelopmental disorders after he had been treated with the drug prior to conception.

Approval status

Off-label uses

In 2012, pharmaceutical company Abbott paid $1.6 billion in fines to US federal and state governments for illegal promotion of off-label uses for Depakote, including the sedation of elderly nursing home residents.

Some studies have suggested that valproate may reopen the critical period for learning absolute pitch and possibly other skills such as language.

Formulations

Valproate exists in two main molecular variants: sodium valproate and valproic acid without sodium (often implied by simply valproate). A mixture between these two is termed semisodium valproate. It is unclear whether there is any difference in efficacy between these variants, except from the fact that about 10% more mass of sodium valproate is needed than valproic acid without sodium to compensate for the sodium itself. In Europe, the US, and many other countries three variants of valproate are sold: valproic acid, sodium valproate and valproate semisodium also known as divalproex sodium, the latter is believed to have fewer gastrointestinal side-effects. Divalproex sodium tablets are a formulation comprising valproate sodium and valproic acid in a 1:1 molar relationship.

Magnesium valproate is also available in China.

Terminology

Valproate is a negative ion. The conjugate acid of valproate is valproic acid (VPA). Valproic acid is fully ionized into valproate at the physiologic pH of the human body, and valproate is the active form of the drug. Sodium valproate is the sodium salt of valproic acid. Divalproex sodium is a coordination complex composed of equal parts of valproic acid and sodium valproate.

Brand names of valproic acid

Branded products include:

• Absenor (Orion Corporation Finland)
• Convulex (G.L. Pharma GmbH Austria)
• Depakene (Abbott Laboratories in US and Canada)
• Depakin (Sanofi S.R.L. Italy)
• Depakine (Sanofi Aventis France)
• Depakine (Sanofi Synthelabo Romania)
• Depalept (Sanofi Aventis Israel)
• Deprakine (Sanofi Aventis Finland)
• Encorate (Sun Pharmaceuticals India)
• Epilim (Sanofi Synthelabo Australia and South Africa)
• Stavzor (Noven Pharmaceuticals Inc.)
• Valcote (Abbott Laboratories Argentina)
• Valpakine (Sanofi Aventis Brazil)
• Orfiril (Desitin Arzneimittel GmbH Norway)

Brand names of sodium valproate

Portugal

• Tablets – Diplexil-R by Bial.

United States

• Intravenous injection – Depacon by Abbott Laboratories.
• Syrup – Depakene by Abbott Laboratories. (Note: Depakene capsules are valproic acid).
• Depakote tablets are a mixture of sodium valproate and valproic acid.
• Tablets – Eliaxim by Bial.

Australia

• Epilim Crushable Tablets Sanofi
• Epilim Sugar Free Liquid Sanofi
• Epilim Syrup Sanofi
• Epilim Tablets Sanofi
• Sodium Valproate Sandoz Tablets Sanofi
• Valpro Tablets Alphapharm
• Valproate Winthrop Tablets Sanofi
• Valprease tablets Sigma

New Zealand

• Epilim by Sanofi-Aventis

All the above formulations are Pharmac-subsidised.

UK

• Depakote Tablets (as in USA)
• Tablets – Orlept by Wockhardt and Epilim by Sanofi
• Oral solution – Orlept Sugar Free by Wockhardt and Epilim by Sanofi
• Syrup – Epilim by Sanofi-Aventis
• Intravenous injection – Epilim Intravenous by Sanofi
• Extended release tablets – Epilim Chrono by Sanofi is a combination of sodium valproate and valproic acid in a 2.3:1 ratio.
• Enteric-coated tablets – Epilim EC200 by Sanofi is a 200 mg sodium valproate enteric-coated tablet.

UK only

• Capsules – Episenta prolonged release by Beacon
• Sachets – Episenta prolonged release by Beacon
• Intravenous solution for injection – Episenta solution for injection by Beacon

Germany, Switzerland, Norway, Finland, Sweden

• Tablets – Orfiril by Desitin Pharmaceuticals
• Intravenous injection – Orfiril IV by Desitin Pharmaceuticals

South Africa

• Syrup – Convulex by Byk Madaus
• Tablets – Epilim by Sanofi-synthelabo

Malaysia

• Tablets – Epilim (200 ENTERIC COATED) by Sanofi-Aventis
• Controlled release tablets – Epilim Chrono (500 CONTROLLED RELEASE) by Sanofi-Aventis

Romania

• Companies are SANOFI-AVENTIS FRANCE, GEROT PHARMAZEUTIKA GMBH and DESITIN ARZNEIMITTEL GMBH
• Types are Syrup, Extended release mini tablets, Gastric resistant coated tablets, Gastric resistant soft capsules, Extended release capsules, Extended release tablets and Extended release coated tablets

Canada

• Intravenous injection – Epival or Epiject by Abbott Laboratories.
• Syrup – Depakene by Abbott Laboratories its generic formulations include Apo-Valproic and ratio-Valproic.

Japan

• Tablets – Depakene by Kyowa Hakko Kirin
• Extended release tablets – Depakene-R by Kyowa Hakko Kogyo and Selenica-R by Kowa
• Syrup – Depakene by Kyowa Hakko Kogyo

Europe

In much of Europe, Dépakine and Depakine Chrono (tablets) are equivalent to Epilim and Epilim Chrono above.

Taiwan

• Tablets (white round tablet) – Depakine (Chinese: 帝拔癲; pinyin: di-ba-dian) by Sanofi Winthrop Industrie (France)

Iran

• Tablets – Epival 200 (enteric coated tablet) and Epival 500 (extended release tablet) by Iran Najo
• Slow release tablets – Depakine Chrono by Sanofi Winthrop Industrie (France)

Israel

Depalept and Depalept Chrono (extended release tablets) are equivalent to Epilim and Epilim Chrono above. Manufactured and distributed by Sanofi-Aventis.

India, Russia and CIS countries

• Valparin Chrono by Sanofi India
• Valprol CR by Intas Pharmaceutical (India)
• Encorate Chrono by Sun Pharmaceutical (India)
• Serven Chrono by Leeven APL Biotech (India)

Uruguay

• Tablets – DI DPA by Megalabs

Brand names of valproate semisodium

• Brazil – Depakote by Abbott Laboratories and Torval CR by Torrent do Brasil
• Canada – Epival by Abbott Laboratories
• Mexico – Epival and Epival ER (extended release) by Abbott Laboratories
• United Kingdom – Depakote (for psychiatric conditions) and Epilim (for epilepsy) by Sanofi-Aventis and generics
• United States – Depakote and Depakote ER (extended release) by Abbott Laboratories and generics
• India – Valance and Valance OD by Abbott Healthcare Pvt Ltd, Divalid ER by Linux laboratories Pvt Ltd, Valex ER by Sigmund Promedica, Dicorate by Sun Pharma
• Germany – Ergenyl Chrono by Sanofi-Aventis and generics
• Chile – Valcote and Valcote ER by Abbott Laboratories
• France and other European countries – Depakote
• Peru – Divalprax by AC Farma Laboratories
• China – Diprate OD

Research

A 2023 systematic review of the literature identified only one study in which valproate was evaluated in the treatment of seizures in infants aged 1 to 36 months. In a randomized control trial, valproate alone was found to show poorer outcomes for infants than valproate plus levetiracetam in terms of reduction of seizures, freedom from seizures, daily living ability, quality of life, and cognitive abilities.