Interaction between Valproic acid and Cannabidiol
Moderate Synergy

ID DDInter1913 and DDInter284
Interaction Coadministration of cannabidiol with other agents known to induce hepatotoxicity may potentiate the risk of liver injury. Cannabidiol causes dose-related elevations of liver transaminases, both alanine aminotransferase (ALT) and aspartate aminotransferase (AST).
Management Caution is advised if cannabidiol is used in patients who are currently receiving or have recently received treatment with other hepatotoxic agents, and vice versa. Serum transaminases and total bilirubin levels should be obtained prior to initiating cannabidiol, and patients with elevated baseline transaminase levels above 3 times the ULN accompanied by elevations in bilirubin above 2 times the ULN should be evaluated. Patients who develop clinical signs or symptoms suggestive of hepatic dysfunction (e.g., unexplained nausea, vomiting, right upper quadrant abdominal pain, fatigue, anorexia, jaundice, dark urine) should have serum transaminases and total bilirubin measured promptly, and cannabidiol treatment interrupted or discontinued as appropriate. Cannabidiol should be discontinued in patients with elevations of transaminase levels greater than 3 times the ULN and bilirubin levels greater than 2 times the ULN. Patients with sustained transaminase elevations of greater than 5 times the ULN should also have treatment discontinued. Patients with prolonged elevations of serum transaminases should be evaluated for other possible causes. Also consider dosage adjustment or discontinuation of any coadministered medication that is known to affect the liver.
References
Alternative for Valproic acid N03A
Alternative for Cannabidiol N03A

Potential Metabolism Interactions

Substrate-Substrate Interaction:If more than one drug is metabolized by the same CYP, it is possible that its metabolism is inhibited because of the competition between the drugs. That means, it can be useful to lower the dosage of the drugs in the drug-cocktail because they remain longer in the organism than in monotherapy.
Inhibitor-Inhibitor Interaction:Combining two or more inhibitors of one CYP, should be compensated by lowering the dosage of these drugs because the metabolism is reduced and the drugs remain longer in the organism than in monotherapy. Not adapting the dosage bears the risk of even more side effects.
Inhibitor-Substrate Interaction:Combining drugs that have inhibitory effect and are substrates of one particular CYP, should be compensated by lowering the dosage. They rest longer in the organism than in monotherapy. Not adapting the dosage bears the risk of even more side effects.