What the FDA labels say about taking them together
Carbamazepine and efavirenz
Efavirenz's FDA label of March 31, 2024 names carbamazepine in its drug interactions section; the carbamazepine labels PlainMeds reads (3) do not name efavirenz. The efavirenz label: “There are insufficient data to make a dose recommendation for efavirenz. Alternative anticonvulsant treatment should be used. Potential for reduction in anticonvulsant and/or efavirenz plasma levels; …”
Check it at the source: the carbamazepine FDA label on DailyMed (effective August 20, 2026, Novartis Pharmaceuticals Corporation); the efavirenz FDA label on DailyMed (effective March 31, 2024, Cipla USA Inc.).
What does the carbamazepine label say about efavirenz?
Carbamazepine's label (effective August 20, 2026) and its 2 other brand-application labels do not name efavirenz in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Tegretol), Novartis Pharmaceuticals Corporation, effective August 20, 2026 (SPL set 8d409411-aa9f-4f3a-a52c-fbcb0c3ec053), via openFDA; the full label on DailyMed
What does the efavirenz label say about carbamazepine?
Efavirenz label, drug interactionsConcomitant Drug Class/Drug Name: Anticonvulsants:Carbamazepine Phenytoin Phenobarbital; Effect: ↓ carbamazepine * ↓ efavirenz * ↓ anticonvulsant ↓ efavirenz; Clinical Comment: There are insufficient data to make a dose recommendation for efavirenz. Alternative anticonvulsant treatment should be used. Potential for reduction in anticonvulsant and/or efavirenz plasma levels; periodic monitoring of anticonvulsant plasma levels should be conducted.
Source: FDA drug label (Efavirenz), Cipla USA Inc., effective March 31, 2024 (SPL set 92603fa5-7a2c-4bfb-9a70-aadb4fba952c), via openFDA; the full label on DailyMed
These are the labels' own sentences. PlainMeds does not grade interactions; a pharmacist or prescriber can say what they mean for one person's medicines.
Both medicines on the record
| Carbamazepine | Efavirenz | |
|---|---|---|
| Labeled for | Bipolar disorder, Seizures and epilepsy | HIV |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | $0.119 per tablet 200 mg tablet | $1.28 per tablet 600 mg tablet |
| Shortage now | A presentation being discontinued | No current entry |
Source: FDA NDC Directory, CMS NADAC of October 7, 2026 and the FDA Drug Shortage Database (FDA files October 8, 2026)
What next?
- Check more medicines together
- up to five at once