Nafcillin
NALLPEN
What it isPenicillinase-resistant penicillin; methicillin-susceptible staphylococcal infection.
Why this oneIts unusual distinction among antibiotics is enzyme induction strong enough to undermine warfarin.
What limits itPhlebitis and extravasation injury can end IV therapy; renal adjustment is unnecessary.
FDA-approved for
- staphylococcal infections (MSSA) (1964)
FDA label
Read the full label on DailyMed ↗
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Staphylococcal / susceptible infection | adult | 500 mg IV q4h; 1 g q4h for severe infection | ||
| Staphylococcal / susceptible infection (IM) | adult | 500 mg IM q4–6h | ||
| Susceptible infection | infants & children <40 kg | 25 mg/kg IM BID | ||
| Susceptible infection | neonates | 10 mg/kg IM BID |
Renal No adjustment needed, including patients on hemodialysis
Hepatic Undefined
Instructions
- Administer IV slowly over at least 30–60 min to minimize vein irritation and extravasation
- Do not add supplementary medication to nafcillin
- Continue therapy ≥14 days for severe staphylococcal infections
- Inspect visually for particulate matter and discoloration before use
Contraindications
- History of anaphylactic reaction to any penicillin
Cautions
- Serious/fatal hypersensitivity (anaphylaxis)
- Severe tissue necrosis/sloughing with extravasation; thrombophlebitis
- Interstitial nephritis
- Neurotoxicity with high doses (esp. hepatic + renal impairment)
- Pseudomembranous colitis
- Neutropenia/bone marrow depression
Adverse reactions
- Allergic reactions (urticaria, pruritus, fever)
- Injection-site pain/phlebitis/thrombophlebitis
- GI upset (nausea, vomiting, diarrhea)
- Elevated liver transaminases
- Interstitial nephritis
- Neutropenia
Pregnancy Undefined
Lactation Undefined
NO BOXED WARNINGS
Principal riskIt INDUCES CYP3A4, so warfarin fails
Cost, est. cash$10–$500/month
Generic entryBy 2023
Classes and tags
Clinical profile
Legacy pregnancy categoryB
Defining liabilityAllergy, gastrointestinal effects and agent-specific renal, hepatic, hematologic or interaction risks.
Mechanism of action: Nafcillin ballicule
