Clonazepam and Felbamate interaction
Clonazepam and Felbamate: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Felbamate (Felbatol) label · effective 2025-08-15
IT IS NOT KNOWN WHETHER CONCOMITANT USE OF OTHER ANTIEPILEPTIC DRUGS AND/OR OTHER DRUGS AFFECT THE INCIDENCE OF HEPATIC FAILURE.
Use in Conjunction with Other Antiepileptic Drugs (see DOSAGE AND ADMINISTRATION ) The addition of Felbatol ® to antiepileptic drugs (AEDs) affects the steady-state plasma concentrations of AEDs.
CBZ epoxide ↓ ↑ ↓ Phenobarbital ↑ ↓ Specific Effects of Felbatol® on Other Antiepileptic Drugs Phenytoin Felbatol ® causes an increase in steady-state phenytoin plasma concentrations.
Effects of Other Antiepileptic Drugs on Felbatol ® Phenytoin Phenytoin causes an approximate doubling of the clearance of Felbatol ® (felbamate) at steady-state and, therefore, the addition of phenytoin causes an approximate 45% decrease in the steady-state trough concentrations of Felbatol ® as compared to the same dose of Felbatol ® given as monotherapy.
The net effect of these interactions is summarized in Table 2: Table 2 Steady-State Plasma Concentrations of Felbatol When Coadministered With Other AEDs AED Coadministered AED Concentration Felbatol ® Concentration Phenytoin ↑ ↓ Valproate ↑ ↔ No significant effect.
From the Clonazepam (Klonopin) label · effective 2025-12-01
They should also be warned about the concomitant use of alcohol or other CNS-depressant drugs during Klonopin therapy (see PRECAUTIONS: Drug Interactions and PRECAUTIONS: Information for Patients ).
…Interactions The CNS-depressant action of the benzodiazepine class of drugs may be potentiated by alcohol, narcotics, barbiturates, nonbarbiturate hypnotics, antianxiety agents, the phenothiazines, thioxanthene and butyrophenone classes of antipsychotic agents, monoamine oxidase inhibitors and the tricyclic antidepressants, and by other anticonvulsant drugs.
The selective serotonin reuptake inhibitors sertraline (weak CYP3A4 inducer) and fluoxetine (CYP2D6 inhibitor), and the anti-epileptic drug felbamate (CYP2C19 inhibitor and CYP3A4 inducer) do not affect the pharmacokinetics of clonazepam.
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.