What the FDA labels say about taking them together
Codeine and rifampin
Codeine's FDA label of December 22, 2025 names rifampin in its drug interactions section; the rifampin label PlainMeds reads does not name codeine. The codeine label: “Codeine is metabolized by CYP2D6 to form morphine. The concomitant use of Codeine Sulfate Tablets and CYP2D6 inhibitors can increase the plasma concentration of codeine, but can decrease the plasma concentration of …”
Check it at the source: the codeine FDA label on DailyMed (effective December 22, 2025, Hikma Pharmaceuticals USA Inc.); the rifampin FDA label on DailyMed (effective February 11, 2026, Lupin Pharmaceuticals, Inc.).
What does the codeine label say about rifampin?
Codeine label, drug interactionsRifampin, carbamazepine, phenytoin Inhibitors of CYP2D6 Clinical Impact: Codeine is metabolized by CYP2D6 to form morphine. The concomitant use of Codeine Sulfate Tablets and CYP2D6 inhibitors can increase the plasma concentration of codeine, but can decrease the plasma concentration of active metabolite morphine, which could result in reduced analgesic efficacy or symptoms of opioid withdrawal … Intervention: If concomitant use with a CYP2D6 inhibitor is necessary, or if a CYP2D6 inhibitor is discontinued after concomitant use, consider dosage adjustment of Codeine Sulfate Tablets and evaluate patients at frequent intervals. …
Codeine label, warnings and precautionsCytochrome P450 3A4 Interaction: The concomitant use of Codeine Sulfate Tablets with all cytochrome P450 3A4 inhibitors, such as macrolide antibiotics (e.g., erythromycin), azole-antifungal agents (e.g., ketoconazole), and protease inhibitors (e.g., ritonavir) or discontinuation of a cytochrome P450 3A4 inducer such as rifampin, carbamazepine, and phenytoin, may result in an increase in codeine plasma concentrations with subsequently greater metabolism by cytochrome P450 2D6, resulting in greater morphine levels, which could increase or prolong adverse reactions and may cause potentially fatal respiratory depression.
Source: FDA drug label (Codeine sulfate), Hikma Pharmaceuticals USA Inc., effective December 22, 2025 (SPL set 010905f9-3bcb-4b50-9fe8-a3ad0010f14c), via openFDA; the full label on DailyMed
What does the rifampin label say about codeine?
Rifampin's label (effective February 11, 2026) does not name codeine in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (rifampin), Lupin Pharmaceuticals, Inc., effective February 11, 2026 (SPL set b56004f0-f23d-47f6-80c7-39884fccbccc), 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
| Codeine | Rifampin | |
|---|---|---|
| Labeled for | Pain | n/a |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | $0.726 per tablet 30 mg tablet | $0.679 per capsule 300 mg capsule |
| Shortage now | No current entry | In shortage |
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