Phenobarbital and Voriconazole interaction
Phenobarbital and Voriconazole: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Phenobarbital (SEZABY) label · effective 2025-12-23
Drugs that Prolong the QT Interval : Avoid concomitant use.
QT Prolongation SEZABY may prolong the QT interval [see Clinical Pharmacology (12.2)] .
Drugs that Prolong QT Interval SEZABY may prolong the QT interval [see Warnings and Precautions (5.10) and Clinical Pharmacology (12.2)] .
Other products that may also prolong the QTc interval may have additive effects, and products that may increase concentrations of phenobarbital [see Drug Interactions (7.1)] may increase the QT prolongation risk; therefore, avoid concomitant use of SEZABY and these products.
From the Voriconazole label · effective 2026-06-02
Carbamazepine (CYP450 Induction) Not Studied In Vivo or In Vitro , but Likely to Result in Significant Reduction Contraindicated Long Acting Barbiturates (e.g., phenobarbital, mephobarbital) (CYP450 Induction) Not Studied In Vivo or In Vitro , but Likely to Result in Significant Reduction Contraindicated Phenytoin (CYP450 Induction) Significantly Reduced Increase…
• Long-acting barbiturates • Rifabutin • Rifampin • Ritonavir Concomitant use with high-dose ritonavir (400 mg every 12 hours) is contraindicated.
Eszopiclone (CYP3A4 Inhibition) Not Studied In Vivo or In Vitro , but Drug Plasma Exposure Likely to be Increased which may Increase the Sedative Effect of Eszopiclone Dose reduction of eszopiclone is recommended.
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.