Isotretinoin and Phenytoin Interaction
Drug interaction information between Isotretinoin and Phenytoin.
Isotretinoin and Phenytoin have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Isotretinoin and Phenytoin. 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
Both drugs may have an effect on bone strength, though it is not certain if taking them together increases the risk of bone loss.
FDA Label Information
Phenytoin : Isotretinoin capsules have not been shown to alter the pharmacokinetics of phenytoin in a study in seven healthy volunteers. Phenytoin is known to cause osteomalacia. No formal clinical studies have been conducted to assess if there is an interactive effect on bone loss between phenytoin and isotretinoin capsules.
Isotretinoin Also Interacts With
- Progesterone major
- Retinol moderate
- Estradiol minor
- Norethindrone minor
- Minocycline minor
Phenytoin Also Interacts With
- Nirmatrelvir/Ritonavir major
- Posaconazole major
- Ranolazine major
- Voriconazole major
- Apixaban moderate
Frequently Asked Questions
What SPL severity band is on file for Isotretinoin + Phenytoin?
Compiled FDA labeling labels this pair minor. That is a source-record field, not an individual medication-combination decision.
Which drug in this pair has the larger labeled-interaction portfolio?
Phenytoin has 147 labeled pairs on file vs Isotretinoin's 7. In the minor band specifically: Isotretinoin has 5 (also Estradiol, Norethindrone, Minocycline, Prenatal Multivitamin); Phenytoin has 120 (also Atorvastatin, Omeprazole, Simvastatin, Methylphenidate).
What mechanism field is on file for Isotretinoin and Phenytoin?
Both drugs may have an effect on bone strength, though it is not certain if taking them together increases the risk of bone loss.
Phenytoin carries more major-labeled pairs than Isotretinoin
SPL source-record counts only. This page's band is minor · classes on file: Isotretinoin (Systemic Retinoid); Phenytoin (Anticonvulsant (Hydantoin)).
Phenytoin has 4 major-labeled pairs vs Isotretinoin's 1. This page itself is in the minor band, not the major band.
1 major · 1 moderate · 5 minor · 7 total
- Other minor peers for Isotretinoin
- Estradiol
- Norethindrone
- Minocycline
- Prenatal Multivitamin
4 major · 23 moderate · 120 minor · 147 total
- Other minor peers for Phenytoin
- Atorvastatin
- Omeprazole
- Simvastatin
- Methylphenidate
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.