Prescription medicine
Nafcillin First approved as Unipen
Nafcillin (Unipen) is a prescription medicine with an FDA approval on record since 1965. FDA's NDC Directory lists it from 9 generic labelers.
- Generic listed
Check it at the source: the nafcillin FDA label on DailyMed (effective March 9, 2026, ONESOURCE SPECIALTY PHARMA LIMITED); the NDA 50199 record on Drugs@FDA; every nafcillin label on DailyMed.
Highlights of the record
FDA label of March 9, 2026; NDC Directory, Drugs@FDA and Orange Book, October 8, 2026
Used for
From the label: indications and usageNafcillin is indicated in the treatment of infections caused by penicillinase-producing staphylococci which have demonstrated susceptibility to the drug.
Forms and strengths
- 1 g
- 2 g
- 10 g
- 1 g/4ml
- 2 g/8ml
- 2 g/100ml
- 10 g/100ml
Injection (powder) for solution; injection (powder) (lyophilized) for solution; injection (solution).
On the market
- Earliest approval on file
- October 11, 1965 Unipen, Wyeth Ayerst; Drugs@FDA’s file, where older or withdrawn approvals can be missing
- Generic approvals
- 16 first August 2, 1984; 9 with a marketed status in Drugs@FDA
- Labelers listed (NDC)
- 10 of which 9 under generic applications, 1 under brand applications, repackagers included
Supply and safety
- Pharmacy cost (NADAC)
- Not in the survey
- Shortage (FDA)
- No current entry
- Recalls by its makers (FDA)
- 3 since 2023 0 Class I among all firms' recalls; latest May 19, 2023
- FAERS reports
- 918 through July 30, 2026
What is nafcillin used for?
From the label: indications and usageNafcillin is indicated in the treatment of infections caused by penicillinase-producing staphylococci which have demonstrated susceptibility to the drug. Culture and susceptibility tests should be performed initially to determine the causative organism and its susceptibility to the drug (see CLINICAL PHARMACOLOGY – Susceptibility Test Methods. Nafcillin should not be used in infections caused by organisms susceptible to penicillin G. If the susceptibility tests indicate that the infection is due to methicillin-resistant Staphylococcus sp., therapy with Nafcillin for Injection, USP should be discontinued and alternative therapy provided. […]
FDA pharmacologic class: Penicillin-class Antibacterial.
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
Is there a generic for nafcillin (Unipen)?
The FDA approved the first generic nafcillin on August 2, 1984. 16 generic applications are approved; 9 of them carry a current (not discontinued) marketing status in Drugs@FDA; that status is not evidence that the generic is on sale.
FDA's NDC Directory lists nafcillin from 9 labelers under a generic (ANDA) application and from 1 brand labeler. A listing means the company has registered the product for sale; it does not show that every pharmacy stocks it.
- 1965 earliest approval on file
- 1984 first generic approved
- red ticks recalls
Source: Drugs@FDA, FDA NDC Directory and the Orange Book (openFDA bulk files, October 8, 2026)
Has nafcillin been recalled?
The FDA's Enforcement Report lists 3 recalls naming nafcillin since 2023: 0 Class I (the most serious), 3 Class II, 0 Class III; 3 still ongoing. A recall names products and lots, not every product of the medicine.
| Started | Class | Company | Reason |
|---|---|---|---|
| May 19, 2023 | Class II | Sagent Pharmaceuticals Inc | Lack of Assurance of Sterility |
Source: FDA Enforcement Report (drug recalls) via openFDA, through October 8, 2026
What does the nafcillin label say about other medicines?
The nafcillin label names 3 other medicines in its interaction, contraindication or warning sections. The labels of 8 other medicines name nafcillin. The sentences are the labels' own; a label lists what its studies and reports found, not every interaction.
| Medicine named | Section | What the label says |
|---|---|---|
| Cyclosporine | drug interactions | Nafcillin when administered concomitantly with cyclosporine has been reported to result in subtherapeutic cyclosporine levels. |
| Tetracycline | drug interactions | Drug Interactions Tetracycline, a bacteriostatic antibiotic, may antagonize the bactericidal effect of penicillin, and concurrent use of these drugs should be avoided. |
| Warfarin | drug interactions | Nafcillin in high dosage regimens, i.e., 2 grams every 4 hours, has been reported to decrease the effects of warfarin. |
Other labels that name nafcillin
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 do FAERS reports show for nafcillin?
The FDA Adverse Event Reporting System holds 918 reports that list nafcillin among the medicines taken, through July 30, 2026, each a report of something that happened, not proof the medicine caused it; 110 are coded as a death and 465 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is.
Reports received each year
The most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026
What next?
- Other penicillins
- the pharmacologic class, with prices and generics
- Nafcillin side effects
- the label's list beside FAERS reports
- Check an interaction
- what two or more labels say about each other