Drug interactions
Cabotegravir + Phenytoin
Severity: Contraindicated
Cabotegravir and Phenytoin: contraindicated interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Phenytoin substantially reduces cabotegravir concentrations, which may cause loss of virologic response and integrase inhibitor resistance. This applies to oral and long-acting injectable forms.
What this interaction means in plain words
Cabotegravir and Phenytoin are not normally used together. Taking them at the same time is expected to cause harm or make one of them unsafe, so a different medicine is usually chosen for one of the two.
Cabotegravir belongs to Anti Virals; Phenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces UGT1A1 and UGT1A9, the main enzymes eliminating cabotegravir.
What to do
Do not co-administer; select a non-inducing anticonvulsant. Inducer effects can persist for weeks after phenytoin is stopped, so delay cabotegravir accordingly.
What to ask your pharmacist
- Is there an alternative to one of these two medicines for me?
- If both are essential, who is monitoring me and how often?
- Which symptoms mean I should stop and seek help straight away?
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Other interactions of Phenytoin
- Artemether / lumefantrine + Phenytoin Contraindicated
- Bictegravir + Phenytoin Contraindicated
- Doravirine + Phenytoin Contraindicated
- Elbasvir / grazoprevir + Phenytoin Contraindicated
- Elvitegravir / cobicistat / emtricitabine / tenofovir df + Phenytoin Contraindicated
- Ensitrelvir + Phenytoin Contraindicated
Other interactions of Cabotegravir
- Apalutamide + Cabotegravir Contraindicated
- Cabotegravir + Carbamazepine Contraindicated
- Cabotegravir + Oxcarbazepine Contraindicated
- Cabotegravir + Phenobarbitone Contraindicated
- Cabotegravir + Rifabutin Contraindicated
- Cabotegravir + Rifampicin Contraindicated
Frequently asked questions
Can I take Cabotegravir with Phenytoin?
MediHelp rates the interaction as contraindicated. Cabotegravir and Phenytoin are not normally used together. Taking them at the same time is expected to cause harm or make one of them unsafe, so a different medicine is usually chosen for one of the two. Phenytoin substantially reduces cabotegravir concentrations, which may cause loss of virologic response and integrase inhibitor resistance. This applies to oral and long-acting injectable forms.
How serious is the interaction between Cabotegravir and Phenytoin?
MediHelp rates it contraindicated, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Do not co-administer; select a non-inducing anticonvulsant. Inducer effects can persist for weeks after phenytoin is stopped, so delay cabotegravir accordingly.
What other medicines interact with Phenytoin?
MediHelp also lists interactions of Phenytoin with, for example, Artemether / lumefantrine, Bictegravir, Doravirine. The full list is on the Phenytoin page.
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