Medication·Interactions & depletion·Reviewed June 9, 2026
Phenobarbital interactions.
Phenobarbital has 4 documented interactions in the NutriStack database, including 1 flagged to avoid or as a serious conflict. Prolonged use is also associated with lower Vitamin D, Calcium, and Folate. The full interaction list, depletion table, and replacement suggestions are below. None of this is a substitute for your prescriber's advice.
Phenobarbital at a glance.
A quick, data-grounded summary. The full tables are below.
Phenobarbital has 4 documented interactions in the NutriStack database, including 1 flagged to avoid or as a serious conflict. Prolonged use is also associated with lower Vitamin D, Calcium, and Folate. The full interaction list, depletion table, and replacement suggestions are below. None of this is a substitute for your prescriber's advice.
Substances that interact with phenobarbital.
Every supplement and medication in the NutriStack database with a documented interaction with this drug, highest-severity first. Open any pair for the mechanism and sources.
| Substance | Interaction | What happens |
|---|---|---|
| Ginkgo Biloba | Conflict | Ginkgo has seizure case reports and may undermine seizure control. |
| Ashwagandha | Caution | Ashwagandha may be sedating and can compound phenobarbital CNS depression. |
| L-Theanine | Caution | L-Theanine may add calming or sedating effects to phenobarbital. |
| Melatonin | Caution | Melatonin can add to phenobarbital sedation and psychomotor impairment. |
What phenobarbital can deplete.
Nutrients this medication is associated with lowering over time, with the mechanism, a suggested replacement where one applies, and the biomarker to monitor. Discuss any replacement with your prescriber first.
| Nutrient | Severity | How it happens | Replace with | Monitor |
|---|---|---|---|---|
| Vitamin D | Significant | Phenobarbital induces hepatic enzymes that accelerate vitamin D catabolism, lowering 25-hydroxyvitamin D and reducing calcium absorption. | Vitamin D3 | Serum 25-hydroxyvitamin D |
| Calcium | Moderate | Reduced vitamin D activity decreases intestinal calcium absorption and can contribute to secondary hyperparathyroidism and bone loss. | Calcium | Serum calcium, parathyroid hormone, and bone density when indicated |
| Folate | Moderate | Chronic enzyme-inducing anticonvulsant therapy can lower folate status through altered metabolism and absorption, increasing risk of megaloblastic... | Methylfolate | CBC, serum folate, red blood cell folate, and homocysteine |
The full phenobarbital profile.
Uses, typical dosing, side effects, and the cited evidence for this medication.
Common phenobarbital questions.
Quick answers drawn from the tables above.
What interacts with Phenobarbital?
In the NutriStack database, Phenobarbital has 4 documented interactions. The most notable include Ginkgo Biloba, Ashwagandha, L-Theanine, and Melatonin. Check any specific combination before taking it and confirm with your prescriber.
Which substances should I avoid with Phenobarbital?
Phenobarbital is flagged against 1 substance in the database, including Ginkgo Biloba. These pairings carry a higher risk and should be reviewed with a clinician before combining.
Does Phenobarbital deplete any nutrients?
Phenobarbital is associated with lowering Vitamin D, Calcium, and Folate with prolonged use. Useful biomarkers to monitor include Serum 25-hydroxyvitamin D, Serum calcium, parathyroid hormone, and bone density when indicated, and CBC, serum folate, red blood cell folate, and homocysteine. Ask your prescriber before adding any replacement supplement.
Is it safe to take Ginkgo Biloba with Phenobarbital?
NutriStack classifies the Ginkgo Biloba and Phenobarbital pairing as conflict: Ginkgo has seizure case reports and may undermine seizure control. Avoid ginkgo in patients using phenobarbital for seizures. Always confirm with your prescriber.
Check your whole stack
See how phenobarbital fits your supplements.
NutriStack screens your full routine for interactions and depletions, and updates the moment you change it.