What the FDA labels say about taking them together
Nafcillin and tetracycline
Nafcillin's FDA label (Nafcillin) of December 6, 2024 names tetracycline in its drug interactions section; the tetracycline label PlainMeds reads does not name nafcillin.
Check it at the source: the nafcillin FDA label on DailyMed (effective March 9, 2026, ONESOURCE SPECIALTY PHARMA LIMITED); the tetracycline FDA label on DailyMed (effective March 18, 2025, Heritage Pharmaceuticals Inc. d/b/a Avet Pharmaceuticals Inc.).
What does the nafcillin label say about tetracycline?
Nafcillin label (Baxter Healthcare Corporation, December 6, 2024), drug interactionsDrug Interactions Tetracycline, a bacteriostatic antibiotic, may antagonize the bactericidal effect of penicillin, and concurrent use of these drugs should be avoided.
Source: FDA drug label (Nafcillin, NDA050655), Baxter Healthcare Corporation, effective December 6, 2024 (SPL set cd2d18c5-95a2-4fb4-bd8b-b5d39e2da416), via openFDA
Source: FDA drug label (NAFCILLIN SODIUM), ONESOURCE SPECIALTY PHARMA LIMITED, effective March 9, 2026 (SPL set 4b3b8e52-df96-4886-e063-6294a90ac63f), via openFDA; the full label on DailyMed
What does the tetracycline label say about nafcillin?
Tetracycline's label (effective March 18, 2025) does not name nafcillin in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (tetracycline hydrochloride), Heritage Pharmaceuticals Inc. d/b/a Avet Pharmaceuticals Inc., effective March 18, 2025 (SPL set eaa5b1bd-0927-46e4-b941-32fcc492d258), 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
| Nafcillin | Tetracycline | |
|---|---|---|
| Labeled for | n/a | Bacterial infections |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | n/a | $0.247 per capsule 250 mg capsule |
| Shortage now | No current entry | 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