Phenytoin (Dilantin) and Ketamine Therapy | Tovani Health
Dilantin (Phenytoin) — Anticonvulsant (CYP3A4 inducer)
Verdict at Tovani Health
Strong CYP induction can reduce ketamine exposure; therapeutic-level patients need individual planning.
Phenytoin alongside ketamine requires individual evaluation. Phenytoin strongly induces CYP3A4 and other enzymes, which can substantially lower ketamine plasma levels. Patients on phenytoin for epilepsy should not adjust the medication without their neurologist; we work around the induction and may use higher KAP doses to achieve equivalent effect.
If you take Dilantin regularly and are considering at-home ketamine therapy, the combination is depends on your specific situation. This page covers the brief pharmacologic context and what we do at intake.
How Dilantin interacts with ketamine
Phenytoin induces CYP3A4, CYP2C9, CYP2C19, and others. Long half-life and zero-order kinetics complicate dosing. Ketamine clearance increases with chronic phenytoin therapy.
What we do at intake
Disclose dose, target level, and most recent serum phenytoin level. Do not stop phenytoin for KAP — seizure breakthrough is the bigger risk. We adjust the KAP plan instead.
Bottom line
Phenytoin alongside ketamine requires individual evaluation. Phenytoin strongly induces CYP3A4 and other enzymes, which can substantially lower ketamine plasma levels. Patients on phenytoin for epilepsy should not adjust the medication without their neurologist; we work around the induction and may use higher KAP doses to achieve equivalent effect.
Ready to find out if at-home ketamine fits your situation?
We’ll note that you’re on Dilantin (Phenytoin) at intake. The eligibility check takes 5 minutes and gives you an honest answer about whether at-home ketamine fits your specific situation.
FL and NJ residents only. Benjamin Soffer, DO — Tovani Health.
Sources
The verdict and clinical guidance on this page are based on the following peer-reviewed literature and FDA prescribing information.
- Ketamine: A Review of Clinical Pharmacokinetics and Pharmacodynamics in Anesthetic and Pain Therapy. Peltoniemi MA, Hagelberg NM, Olkkola KT, Saari TI. Clinical Pharmacokinetics. 2016. PMID: 27028535
Clinically reviewed
Reviewed by Benjamin Soffer, DO on May 17, 2026. Dr. Soffer is a board-certified physician (American Board of Internal Medicine) licensed in Florida and New Jersey, prescribing at-home ketamine therapy through Tovani Health.
This page is general information about how this medication interacts with at-home ketamine therapy at Tovani Health. It is not a substitute for medical advice from your prescribing physician about your specific situation. Always discuss medication changes with the doctor who prescribed them.