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nafcillin (Nafcil, Unipen, Nallpen)

Tradenames: Nafcil, Unipen. 2nd generation penicillin. Indications: - treatment of serious bacterial infections - infectious arthritis, osteomyelitis - skin or soft tissue infection - urinary tract infection - respiratory tract infection - bacteremia - empiric treatment for fever of unknown origin [5] - mainly indicated for penicillinase-producing Staphylococci Contraindications: - avoid in patients with hypersensitivity to penicillin Dosage: 1-2 g IV/IM every 4 hours. - 250-500 mg PO every 4-6 hours. Pediatrics: 50 mg/kg/day divided every 4-6 hours Tabs: 250 & 500 mg. Suspension: 250 mg/5 mL. Powder for injection: 500 mg, 1 g, 2 g. Pharmacokinetics: 1) well distributed to most tissues & fluids 2) minimal CSF penetration 3) elimination 1/2life is 1 hour with normal or moderately impaired renal function 4) protein binding 90% 5) 60% is metabolized in the liver 6) most is eliminated in the bile, small amounts in the urine 7) dosage adjustment not necessary with renal insufficiency 8) minimally removed by hemodialysis 9) dose adjustment may be warranted in patients with both hepatic & renal insufficiency Monitor: - weekly monitoring for outpatients on parenteral nafcillin - liver function tests - renal function tests - complete blood count [6] Antimicrobial activity: 1) Staphylococcus aureus (but not methicillin-resistant S. aureus {MRSA}) 2) less active than other penicillins against Streptococcus sp. 3) lacks enterococcus & anaerobic coverage Adverse effects: 1) common (> 10%) - phlebitis or irritation at IV site 2) uncommon (< 1%) - thrombophlebitis, fever, rash, nausea, diarrhea, neutropenia, pain, acute interstitial nephritis, hypersensitivity reactions 3) other [2] 1) blood dyscrasia (rare) 2) elevated serum transaminases 3) seizures (rare) Drug interactions: 1) probenecid increases & prolongs the 1/2life of nafcillin 2) nafcillin induces cyt P450 3A4 -> may diminish levels of drugs metabolized by cyt P450 3A4 Mechanism of action: 1) inhibition of bacterial wall synthesis 2) active against penicillinase-producing organisms

Interactions

drug interactions

Related

cytochrome P450 3A4 (cytochrome P450 C3, nifedipine oxidase, P450-PCN1, NF-25, CYP3A4)

General

2nd generation penicillin (penicillinase-resistant)

Properties

MISC-INFO: elimination route LIVER KIDNEY protein-binding 90% elimination by hemodialysis - pregnancy-category B safety in lactation ?

Database Correlations

PUBCHEM correlations

References

  1. The Pharmacological Basis of Therapeutics, 9th ed. Gilman et al, eds. Permagon Press/McGraw Hill, 1996.
  2. Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998
  3. Kaiser Permanente Northern California Regional Drug Formulary, 1998
  4. Prescriber's Letter 13(3): 2006 Cytochrome P450 drug interactions Detail-Document#: 220233 (subscription needed) http://www.prescribersletter.com
  5. Deprecated Reference
  6. Medical Knowledge Self Assessment Program (MKSAP) 17, American College of Physicians, Philadelphia 2015