Carbamazepine and Phenobarbital interaction
Carbamazepine and Phenobarbital: 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 Carbamazepine (EQUETRO) label · effective 2025-08-19
CNS Depressants The concomitant use of EQUETRO and other CNS depressants can increase the risk of respiratory depression, profound sedation, hypotension, and syncope.
Limited evidence suggests that HLA-B*1502 may be a risk factor for the development of SJS/TEN in patients of Chinese ancestry taking other anti-epileptic drugs associated with SJS/TEN, including phenytoin.
Consider reducing the dose of CNS depressants or EQUETRO when using these drugs concomitantly.
Hypersensitivity Hypersensitivity reactions to carbamazepine have been reported in patients who previously experienced this reaction to anticonvulsants including phenytoin, primidone, and phenobarbital.
Such drugs include the following: Aminophylline, c isplatin, doxorubicin, felbamate, phosphenytoin, methsuximide , phenobarbital, phenytoin, primidone, rifampin and theophylline.
From the Phenobarbital (SEZABY) label · effective 2025-12-23
Additionally, consider alternatives to structurally similar drugs such as carboxamides (e.g., carbamazepine) and hydantoins (e.g., phenytoin) in these same patients.
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.