What the FDA labels say about taking them together
Phenobarbital and ranolazine
Ranolazine's FDA label of January 23, 2026 names phenobarbital in its contraindications section; the phenobarbital labels PlainMeds reads (2) do not name ranolazine. The ranolazine label: “CYP3A Inducers Do not use ranolazine with CYP3A inducers such as rifampin, rifabutin, rifapentine, phenobarbital, phenytoin, carbamazepine, and St. John’s wort.”
Check it at the source: the phenobarbital FDA label on DailyMed (effective August 27, 2026); the ranolazine FDA label on DailyMed (effective January 23, 2026, Glenmark Pharmaceuticals Inc., USA).
What does the phenobarbital label say about ranolazine?
Phenobarbital's label (effective August 27, 2026) and its 1 other brand-application label do not name ranolazine in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Phenobarbital), Chartwell RX, LLC, effective August 27, 2026 (SPL set 74428144-fb24-40a5-a670-3b876e2d116c), via openFDA; the full label on DailyMed
What does the ranolazine label say about phenobarbital?
Ranolazine label, contraindicationsCYP3A inducers (e.g., rifampin, phenobarbital, St. John’s wort)
Ranolazine label, drug interactionsCYP3A Inducers Do not use ranolazine with CYP3A inducers such as rifampin, rifabutin, rifapentine, phenobarbital, phenytoin, carbamazepine, and St. John’s wort [see Contraindications (4), Clinical Pharmacology (12.3) ].
Aspruzyo Sprinkle label (SUN PHARMACEUTICAL INDUSTRIES, INC., January 29, 2025), contraindicationsCONTRAINDICATIONS ASPRUZYO Sprinkle is contraindicated in patients: Taking strong inhibitors of CYP3A [see Drug Interactions (7.1)] Taking inducers of CYP3A [see Drug Interactions (7.1)] With liver cirrhosis [see Use in Specific Populations (8.6)] Strong CYP3A inhibitors (e.g., ketoconazole, clarithromycin, nelfinavir) (4, 7.1) CYP3A inducers (e.g., rifampin, phenobarbital, St. John's wort) (4, 7.1) Liver cirrhosis
Source: FDA drug label (Aspruzyo Sprinkle, NDA216018), SUN PHARMACEUTICAL INDUSTRIES, INC., effective January 29, 2025 (SPL set dd9f81e4-50da-4551-aed5-559d304df42e), via openFDA
Source: FDA drug label (Ranolazine), Glenmark Pharmaceuticals Inc., USA, effective January 23, 2026 (SPL set 0cf58732-c242-49b0-8e3f-248778b4458d), 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
| Phenobarbital | Ranolazine | |
|---|---|---|
| Labeled for | Seizures and epilepsy | Angina |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.213 per tablet 100 mg tablet | $0.165 per tablet 500 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