Phenobarbital and Voriconazole Interaction
Drug interaction information between Phenobarbital and Voriconazole.
Phenobarbital and Voriconazole have a documented major interaction in FDA labeling.
FDA drug labeling documents a major-severity interaction between Phenobarbital and Voriconazole. This page displays the available source-record category and label text. The category is not an individual risk estimate or medication-combination direction.
How They Interact
Phenobarbital causes the body to process voriconazole much faster than normal, which significantly lowers the amount of medicine in your system. This makes the treatment much less likely to fight off an infection.
FDA Label Information
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 voriconazole maintenance dose from 4 mg/kg to 5 mg/kg IV every 12 hours or from 200 mg to 400 mg orally every 12 hours (100 mg to 200 mg orally every 12 hours in patients weighing less than 40 kg).
Phenobarbital Also Interacts With
- Nirmatrelvir/Ritonavir major
- Ranolazine major
- Canagliflozin moderate
- Cenobamate moderate
- Clarithromycin moderate
Voriconazole Also Interacts With
- Norethindrone major
- Rifampin major
- Lurasidone major
- Pimozide major
- Ivabradine major
Frequently Asked Questions
What SPL severity band is on file for Phenobarbital + Voriconazole?
Compiled FDA labeling labels this pair major. That is a source-record field, not an individual medication-combination decision.
Which drug in this pair has the larger labeled-interaction portfolio?
Phenobarbital has 59 labeled pairs on file vs Voriconazole's 50. In the major band specifically: Phenobarbital has 3 (also Nirmatrelvir/Ritonavir, Ranolazine); Voriconazole has 8 (also Norethindrone, Rifampin, Lurasidone, Pimozide).
What mechanism field is on file for Phenobarbital and Voriconazole?
Phenobarbital causes the body to process voriconazole much faster than normal, which significantly lowers the amount of medicine in your system. This makes the treatment much less likely to fight off an infection.
Voriconazole carries more major-labeled pairs than Phenobarbital
SPL source-record counts only. This page's band is major · classes on file: Phenobarbital (Anticonvulsant (Barbiturate)); Voriconazole (Azole Antifungal).
Voriconazole has 8 major-labeled pairs vs Phenobarbital's 3.
3 major · 13 moderate · 43 minor · 59 total
- Other major peers for Phenobarbital
- Nirmatrelvir/Ritonavir
- Ranolazine
8 major · 9 moderate · 33 minor · 50 total
- Other major peers for Voriconazole
- Norethindrone
- Rifampin
- Lurasidone
- Pimozide
Sources: FDA Drug Labels (SPL) via openFDA (2026). This is for informational purposes only and is not medical advice. This registry does not provide individual medication-combination directions.
Read our methodology - how this data is sourced, computed, and verified.