Overview
11 DESCRIPTION Valproic acid is a carboxylic acid designated as 2-propylpentanoic acid. It is also known as dipropylacetic acid. Valproic acid has the following structure: Valproic acid (pKa 4.8) has a molecular weight of 144 and occurs as a colorless liquid with a characteristic odor. It is slightly soluble in water (1.3 mg/mL) and very soluble in organic solvents.
Mechanism of Action
12 CLINICAL PHARMACOLOGY 12.1 Mechanism of Action Valproic acid dissociates to the valproate ion in the gastrointestinal tract. The mechanisms by which valproate exerts its therapeutic effects have not been established. It has been suggested that its activity in epilepsy is related to increased brain concentrations of gamma-aminobutyric acid (GABA). 12.2 Pharmacodynamics The relationship between plasma concentration and clinical response is not well documented. One contributing factor is the nonlinear, concentration dependent protein binding of valproate which affects the clearance of the drug. Thus, monitoring of total serum valproate cannot provide a reliable index of the bioactive valproate species.
Indications
- 1 INDICATIONS AND USAGE Valproic acid oral solution is indicated for: Monotherapy and adjunctive therapy of complex partial seizures; sole and adjunctive therapy of simple and complex absence seizures; adjunctive therapy in patients with multiple seizure types that include absence seizures ( 1 ) 1.1 Epilepsy Valproic acid oral solution is indicated as monotherapy and adjunctive therapy in the treatment of patients with complex partial seizures that occur either in isolation or in association with other types of seizures.
Common Doses
- 15 mg
- 10 mg
- 60 mg
- 100 mcg
Dosage
2 DOSAGE AND ADMINISTRATION Valproic acid oral solution is intended for oral administration. ( 2.1 ) Simple and Complex Absence Seizures: Start at 10 to 15 mg/kg/day, increasing at 1 week intervals by 5 to 10 mg/kg/week until seizure control or limiting side effects ( 2.1 ) Safety of doses above 60 mg/kg/day is not established ( 2.1 , 2.2 ) 2.1 Epilepsy Valproic acid oral solution is intended for oral administration. Patients should be informed to take valproic acid oral solution every day as prescribed.
Black Box Warning
BOXED WARNING Hepatotoxicity General Population: Hepatic failure resulting in fatalities has occurred in patients receiving valproate and its derivatives. These incidents usually have occurred during the first six months of treatment. Serious or fatal hepatotoxicity may be preceded by non-specific symptoms such as malaise, weakness, lethargy, facial edema, anorexia, and vomiting. In patients with epilepsy, a loss of seizure control may also occur. Patients should be monitored closely for appearance of these symptoms.
Contraindications
- 4 CONTRAINDICATIONS Valproic acid should not be administered to patients with hepatic disease or significant hepatic dysfunction [see Warnings and Precautions ( 5.1 )] . Valproic acid is contraindicated in patients known to have mitochondrial disorders caused by mutations in mitochondrial DNA polymerase γ (POLG; e.g., Alpers-Huttenlocher Syndrome) and children under two years of age who are suspected of having a POLG-related disorder [see Warnings and Precautions ( 5.1 )] . Valproic acid is contraindicated in patients with known hypersensitivity to the drug [see Warnings and Precautions ( 5.
Side Effects
- 6 ADVERSE REACTIONS The following serious adverse reactions are described below and elsewhere in the labeling: Hepatic failure [see Warnings and Precautions ( 5.1 )] Birth defects [see Warnings and Precautions ( 5.2 )] Decreased IQ following in utero exposure [see Warnings and Precautions ( 5.3 )] Pancreatitis [see Warnings and Precautions ( 5.5 )] Hyperammonemic encephalopathy [see Warnings and Precautions ( 5.6 , 5.9 , 5.10 )] Suicidal behavior and ideation [see Warnings and Precautions ( 5.7 )] Bleeding and other hematopoietic disorders [see Warnings and Precautions ( 5.
Interactions
- 7 DRUG INTERACTIONS Hepatic enzyme-inducing drugs (e.g., phenytoin, carbamazepine, phenobarbital, primidone, rifampin) can increase valproate clearance, while enzyme inhibitors (e.g., felbamate) can decrease valproate clearance. Therefore increased monitoring of valproate and concomitant drug concentrations and dosage adjustment are indicated whenever enzyme- inducing or inhibiting drugs are introduced or withdrawn ( 7.1 ) Aspirin, carbapenem antibiotics, estrogen-containing hormonal contraceptives: Monitoring of valproate concentrations is recommended ( 7.