Valproate (Valproic Acid / Sodium Valproate)

1. Chemistry and Formulations

2. Mechanism of Action

1. Inhibition of voltage-sensitive sodium channels (VSSCs): Valproate may change the sensitivity of VSSCs, possibly by directly binding to channel subunits or inhibiting phosphorylating enzymes that regulate their sensitivity. This reduces sodium influx and downstream glutamate excitatory neurotransmission - a possible mechanism for antimanic effects.
2. Potentiation of GABAergic neurotransmission: Valproate inhibits the catabolism of GABA, thereby increasing GABAergic inhibition.
3. Downstream signal transduction regulation (Maudsley): Valproate reduces protein kinase C, activates the extracellular signal-regulated kinase (ERK) pathway, promotes BDNF (brain-derived neurotrophic factor) expression, reduces turnover of arachidonic acid, and alters synaptic plasticity. It also depletes inositol and influences non-GABA pathways.

Figure 7-75 from Stahl's: Pharmacological actions of valproic acid. Valproic acid may work by interfering with voltage-sensitive sodium channels, enhancing GABA activity, and regulating downstream signal transduction cascades.

3. Indications (Psychiatric)

A. Mania / Bipolar I Disorder - Acute Mania

• Approved for manic episodes associated with Bipolar I Disorder (Kaplan & Sadock's).
• About two-thirds of patients with acute mania respond to valproate.
• Response usually within 1-4 days after achieving serum concentrations above 50 µg/mL.
• Optimal therapeutic range: 50-125 µg/mL for antimanic response; levels >94 mg/L associated with the most robust response (Maudsley).
• Rapid oral loading strategies can achieve therapeutic serum concentrations in 1 day and control manic symptoms within 5 days.
• NNT = 2-4 for acute mania (Maudsley).
• The irritable manic subtype responds significantly better to valproate than lithium or placebo (Kaplan & Sadock's).
• Preferred over lithium for acute mania in children and elderly due to more favorable cognitive, dermatologic, thyroid, and renal adverse effect profile.

B. Bipolar Depression

• Valproate has some activity in bipolar depressive episodes, but far less pronounced than for mania.
• More useful for agitation than dysphoria within depressive episodes.
• A 2020 meta-analysis placed divalproex 5th out of 21 treatments for bipolar depression (Maudsley).
• In clinical practice, most often used as add-on therapy to an antidepressant to prevent mania or rapid cycling.

C. Prophylaxis (Maintenance)

• Useful in prophylaxis of Bipolar I disorder - fewer, less severe, shorter manic episodes.
• At least as effective as lithium in prophylaxis and better tolerated (Kaplan & Sadock's).
• Particularly useful in:
  • Rapid-cycling and ultrarapid-cycling bipolar disorders
  • Dysphoric or mixed mania
  • Mania due to a general medical condition
  • Comorbid substance use disorders or panic attacks
  • Incomplete response to lithium
• NICE (UK) recommends valproate as a first-line option for acute mania, bipolar depression (with antidepressant), and prophylaxis - but NOT in women of child-bearing potential (Maudsley).
• A Cochrane review noted that evidence supporting prophylactic use is limited.

D. Other Psychiatric Uses

• Schizophrenia/Schizoaffective disorder: May accelerate response to antipsychotic therapy; not effective alone for psychotic symptoms (Kaplan & Sadock's).
• Aggression/Behavioral agitation: Some evidence for reduction of aggressive behavior in various psychiatric conditions; one RCT failed to show advantage over risperidone alone in schizophrenia (Maudsley).
• Studied (weak evidence) in: alcohol withdrawal, panic disorder, PTSD, impulse control disorder, borderline personality disorder (Kaplan & Sadock's).

4. Pharmacokinetics

• Pharmacokinetics are complex, following a three-compartmental model with protein-binding saturation (Maudsley).
• Highly protein-bound (~90-95%); can be displaced by other protein-bound drugs (e.g., aspirin).
• Hepatically metabolized - primarily by glucuronide conjugation and beta-oxidation; CYP enzymes play a minor role.
• Plasma half-life: approximately 9-16 hours (varies by formulation and age).
• Therapeutic range: 50-125 µg/mL (trough, 12 hours post-dose).
• Serum levels <55 mg/L are no more effective than placebo in acute mania (Maudsley).

5. Dosing

• Start low and titrate upwards against response and adverse effects.
• Loading dose regimens (e.g., 20-30 mg/kg/day) are generally well tolerated and achieve therapeutic levels rapidly.
• Controlled-release sodium valproate (Epilim Chrono) can be given once daily; other formulations require at least twice daily dosing.
• Typical maintenance doses: 750-2,000 mg/day in divided doses.

• Full blood count (FBC) and liver function tests (LFTs)
• Baseline weight measurement
• In women: pregnancy test + contraception counseling

• LFTs and FBC at 6 months; BMI monitoring
• More frequent LFTs during the first 6 months; albumin and clotting if enzyme levels are abnormal
• Plasma level monitoring: useful to detect non-compliance or toxicity

6. Adverse Effects

Serious / Black Box Warnings (Kaplan & Sadock's)

Common Adverse Effects

7. Teratogenicity and Use in Women

• Established human teratogen (Maudsley) - contraindicated in women of child-bearing potential in many countries.
• Neural tube defects (e.g., spina bifida): ~1-4% risk in first trimester; risk reduced with folic acid 1-4 mg/day.
• Cognitive effects in offspring: Lower IQ at age 6 years; dose-dependent reduction in cognitive abilities across multiple domains.
• Autism spectrum disorder: Increased risk with in utero exposure.
• Folic acid supplementation is mandatory in all women of child-bearing potential on valproate.
• PCOS: Reported particularly in adolescents and young women; driven by metabolic syndrome/insulin resistance.
• Breastfeeding: Infant serum levels reach 1-10% of maternal; not contraindicated but caution advised.

8. Drug Interactions

9. Contraindications

• Hepatic disease or severe hepatic impairment
• Personal or family history of severe hepatic dysfunction
• Women of child-bearing potential (UK/EU regulatory guidance)
• Known hypersensitivity to valproate
• Mitochondrial disorders (e.g., Alpers' syndrome) - especially in children

10. Discontinuation

• If discontinuing, taper slowly over at least 1 month (preferably longer) to avoid precipitating mood episodes (Maudsley).
• Limited data on whether abrupt discontinuation worsens the natural course of bipolar illness as markedly as with lithium, but caution is warranted.
• In epilepsy, withdrawal of valproate is associated with depression, falls, and hospital admissions.

Summary: Valproate at a Glance

• Kaplan and Sadock's Synopsis of Psychiatry (11th ed.), Chapter 21, pp. 1979-1990
• Stahl's Essential Psychopharmacology (5th ed., Neuroscientific Basis), Chapter 7, pp. 363-370
• The Maudsley Prescribing Guidelines in Psychiatry (15th ed.), Chapter 2 (Valproate), pp. 314-316

VALPROATE

20-Mark Answer

I. INTRODUCTION

II. CHEMISTRY AND FORMULATIONS

III. MECHANISM OF ACTION

A. Inhibition of Voltage-Sensitive Sodium Channels (VSSCs)

B. Potentiation of GABAergic Neurotransmission

C. Downstream Signal Transduction Regulation

• Activates the ERK (extracellular signal-regulated kinase) pathway, altering synaptic plasticity
• Promotes BDNF (brain-derived neurotrophic factor) expression
• Reduces protein kinase C levels
• Reduces turnover of arachidonic acid
• Interferes with intracellular signaling and gene expression (transcription regulation, cytoskeletal modifications, ion homeostasis)
• Depletes inositol (similar to lithium)
• May also interact with voltage-sensitive calcium channels and indirectly reduce glutamate activity

Figure 7-75, Stahl's Essential Psychopharmacology: Valproic acid acts on Na+ channels, GABA, Ca++ channels, and glutamate (Glu) pathways.

IV. PHARMACOKINETICS

• Pharmacokinetics follow a three-compartmental model with protein-binding saturation (Maudsley, p. 315)
• Highly protein-bound (~90-95%); can be displaced by other protein-bound drugs (e.g., aspirin, warfarin)
• Hepatically metabolized - primarily via glucuronide conjugation and beta-oxidation; CYP enzymes play a minor role
• Half-life: approximately 9-16 hours (varies by formulation and age)
• Bioavailability: nearly 100% on oral administration
• Therapeutic plasma range: 50-125 µg/mL (trough level, drawn 12 hours post-dose)
  • Levels <55 mg/L are no more effective than placebo in acute mania
  • Levels >94 mg/L are associated with the most robust antimanic response
  • Maintenance phase optimal levels: likely ≥50 mg/L
• Total (rather than free) valproate concentration is the standard monitoring method and is adequate in most situations

V. INDICATIONS AND CLINICAL USE

A. Bipolar I Disorder - Acute Mania (PRIMARY INDICATION)

• About two-thirds of patients with acute mania respond to valproate (Kaplan & Sadock's, p. 1984)
• Response usually occurs within 1-4 days after achieving serum concentrations >50 µg/mL
• Rapid oral loading strategies achieve therapeutic levels in 1 day, controlling mania within 5 days
• NNT = 2-4 for acute mania (Maudsley, p. 314)
• Antimanic effects can be augmented with lithium, carbamazepine, second-generation antipsychotics (SGAs), or dopamine receptor antagonists (DRAs)
• The irritable manic subtype responds significantly better to valproate than to lithium or placebo
• Preferred over lithium in children and elderly due to more favorable cognitive, dermatologic, thyroid, and renal adverse effect profile

B. Bipolar Depression

• Has some short-term efficacy in bipolar depressive episodes, but far less pronounced than for mania (Kaplan & Sadock's, p. 1984)
• More useful for agitation than dysphoria
• A 2020 meta-analysis placed divalproex 5th out of 21 treatments for bipolar depression
• Commonly used as add-on therapy to an antidepressant to prevent switch to mania or rapid cycling

C. Prophylaxis (Maintenance Therapy)

• Results in fewer, less severe, shorter manic episodes (Kaplan & Sadock's, p. 1984)
• At least as effective as lithium and better tolerated in prophylaxis
• Particularly useful in:
  • Rapid-cycling and ultrarapid-cycling bipolar disorder
  • Dysphoric or mixed mania
  • Mania secondary to a general medical condition
  • Comorbid substance use disorders or panic disorder
  • Incomplete response to lithium
• NICE (UK) recommends valproate as a first-line option for mania, bipolar depression, and prophylaxis - but NOT in women of child-bearing potential (Maudsley, p. 314)
• BALANCE study found lithium numerically superior to valproate alone; the combination of lithium + valproate was statistically superior to valproate alone

D. Schizophrenia and Schizoaffective Disorder

• May accelerate response to antipsychotic therapy
• Not effective alone for psychotic symptoms; typically used in combination (Kaplan & Sadock's, p. 1984)

E. Other Psychiatric Uses (Weak Evidence)

• Alcohol withdrawal and relapse prevention
• Panic disorder
• PTSD
• Impulse control disorder
• Borderline personality disorder
• Behavioral agitation in dementia (one Cochrane review found it ineffective and associated with higher adverse effects)
• Aggression in various psychiatric disorders

VI. DOSING AND MONITORING

Dosing

Pre-treatment Work-up (NICE/Maudsley, p. 315-316)

• Full blood count (FBC)
• Liver function tests (LFTs)
• Baseline weight / BMI
• In women: pregnancy test + contraception counseling + folic acid prescription

On-treatment Monitoring

• LFTs and FBC repeated at 6 months; more frequently in first 6 months if enzyme levels are elevated
• Albumin and clotting measured if LFT abnormality persists
• BMI monitored throughout
• Plasma levels for compliance check, toxicity detection, or dose optimization
• Free valproate levels indicated when significant hypoalbuminaemia is present

VII. ADVERSE EFFECTS

Common

Uncommon

• Persistent elevation of hepatic transaminases (5-40%; usually asymptomatic, reversible)
• Hyperammonaemia (can cause encephalopathy, confusion, lethargy)
• Peripheral oedema

Serious / Black Box Warnings

VIII. TERATOGENICITY AND USE IN WOMEN

• Neural tube defects (e.g., spina bifida): 1-4% risk with first-trimester exposure
• Cognitive effects in offspring: Children exposed in utero have lower IQ scores at age 6 years; dose-dependent reduction across multiple cognitive domains
• Autism spectrum disorder: Increased risk with prenatal valproate exposure
• PCOS in young women on long-term therapy
• Folic acid 1-4 mg/day must be prescribed to all women of child-bearing potential
• Breastfeeding: Infant serum levels reach 1-10% of maternal concentration; not absolutely contraindicated but caution advised

IX. DRUG INTERACTIONS

X. CONTRAINDICATIONS

• Hepatic disease or severe hepatic impairment
• Personal or family history of severe hepatic dysfunction
• Women of child-bearing potential (UK/EU regulatory contraindication)
• Known hypersensitivity to valproate
• Mitochondrial disorders (e.g., Alpers-Huttenlocher syndrome) - particularly in children
• Urea cycle disorders (risk of fatal hyperammonaemic encephalopathy)

XI. DISCONTINUATION

• If discontinuing, taper slowly over at least 1 month (preferably longer) to avoid precipitating mood relapse (Maudsley, p. 316)
• Whether abrupt withdrawal worsens the natural course of bipolar illness as severely as lithium withdrawal is unknown; caution is prudent
• In epilepsy, valproate withdrawal is associated with depression, falls, and hospital admissions

XII. SUMMARY TABLE

REFERENCES

1. Sadock BJ, Sadock VA, Ruiz P. Kaplan and Sadock's Synopsis of Psychiatry. 11th ed. Wolters Kluwer; 2015. Chapter 21, pp. 1979-1990.
2. Stahl SM. Stahl's Essential Psychopharmacology: Neuroscientific Basis and Practical Application. 5th ed. Cambridge University Press; 2021. Chapter 7, pp. 363-370.
3. Taylor D, Barnes TRE, Young AH. The Maudsley Prescribing Guidelines in Psychiatry. 15th ed. Wiley-Blackwell; 2021. Chapter 2 (Valproate), pp. 313-317.