Adding valproic acid to quetiapine.
- Quetiapine is principally metabolized by CYP3A4 to active and inactive metabolites.
- Valproic acid is principally metabolized by CYP2C9, CYP2C19, CYP2A6 and UDP-glucuronosyltransferases. Valproic acid is an inhibitor of the enzymes CYP2C9, epoxide-hydroxylase and UDP-glucuronosyltransferases.
- This combination of drugs may have possible synergistic effects. However, this combination will also have additive side effects. Dose adaptation will be recommended for this combination. 
Start valproic acid
- Start valproic acid according to the general dosing advice.
- During concomitant use of these drugs, patients should be monitored for potentially excessive or prolonged CNS and respiratory depression. 
KNMP; Informatorium Medicamentorum 2015; Monografie "quetiapine" (Dutch)
Cite error: Invalid
<ref>tag; name "informatorium" defined multiple times with different content
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- Farmacotherapeutisch Kompas - valproinezuur (dutch)
- Vieta E at al, Efficacy and safety of quetiapine in combination with lithium or divalproex for maintenance of patients with bipolar I disorder (international trial 126). J Affect Disord. 2008 Aug;109(3):251-63. Epub 2008 Jun 24
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