NAFCILLIN SODIUM
(naf-sill'in)
Nafcil, Nallpen, Unipen
Classifications: antiinfective; beta-lactam antibiotic; penicillin; antistaphylococcal penicillin
Prototype: Penicillin G potassium
Pregnancy Category: B
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250 mg capsules; 500 mg, 1 g, 2 g injection
Semisynthetic, acid-stable, penicillinase-resistant penicillin. Mechanism of bactericidal action is by interfering with synthesis
of mucopeptides essential to formation and integrity of bacterial cell wall.
Effective against both penicillin-sensitive and penicillin-resistant strains of Staphylococcus aureus. Also active against pneumococci and group A beta-hemolytic Streptococci. Highly active against penicillinase-producing Staphylococci but less potent than penicillin G against penicillin-sensitive microorganisms and generally ineffective against Methicillin-Resistant
Staphylococcus aureus (MRSA).
Primarily, infections caused by penicillinase-producing Staphylococci. May also be used to initiate treatment in suspected staphylococcal infections pending culture and sensitivity test results.
As with other penicillins, serum concentrations are considerably enhanced by concurrent use of probenecid.
Hypersensitivity to penicillins, cephalosporins, and other allergens; use of oral drug in severe infections, gastric dilatation,
cardiospasm, or intestinal hypermotility; lactation. Safety during pregnancy (category B) is not established.
History of or suspected atopy or allergy (eczema, hives, hay fever, asthma).
Staphylococcal Infections
Adult: IM/IV 500 mg–2 g q4–6h up to 12 g/d PO 250–1000 mg q4–6h
Child: IM/IV 100–300 mg/kg/d divided q4–6h PO 50–100 mg/kg/d in 4 divided doses
Neonate: IM/IV 50–100 mg/kg/d divided q6–12h
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Oral
- Give on empty stomach (at least 1 h before or 2 h after meals).
Intramuscular
- Reconstitute each 500 mg with 1.7 mL of sterile water for injection or NaCal injection to yield 250 mg/mL. Shake vigorously
to dissolve.
- In adults: Make certain solution is clear. Select site carefully. Inject deeply into gluteal muscle. Rotate injection sites.
- In children: The preferred IM site in children <3 y is the midlateral or anterolateral thigh. Check agency policy.
- Label and date vials of reconstituted solution. Remains stable for 7 d under refrigeration and for 3 d at 15°–30°
C (59°–86° F).
Intravenous
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Note: Verify correct IV concentration and rate of infusion in neonates, infants, children with physician.
PREPARE: Direct: Reconstitute as for IM injection. Further dilute with 15–30 mL of D5W, NS, or 0.45% NaCl. Intermittent: Dilute reconstituted solution in 100–150 mL of compatible IV solution. Continuous: Add desired dose to a volume of IV solution that maintains concentration of drug between 2–40 mg/mL.
ADMINISTER: Direct: Give over at least 10 min. Intermittent: Give over 30–90 min. Continuous: Give at ordered rate.
INCOMPATIBILITIES Solution/additive:
Aminophylline,
ascorbic acid,
aztreonam,
bleomycin,
cytarabine,
hydrocortisone,
methylprednisolone,
promazine.
Y-site:
Droperidol,
Innovar,
labetalol,
nalbuphine,
pentazocine,
verapamil.
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Note: Usually, limit IV therapy to 24–48 h because of the possibility of thrombophlebitis (see Appendix F), particularly in
older adults.
- Discard unused portions 24 h after reconstitution.
Body as a Whole: Drug fever, anaphylaxis (particularly following parenteral therapy). GI: Nausea, vomiting, diarrhea, increase in serum transaminase activity (following IM). Hematologic: Eosinophilia, thrombophlebitis following IV; neutropenia (long-term therapy). Metabolic: Hypokalemia (with high IV doses). Skin: Urticaria, pruritus, rash, pain and tissue irritation. Urogenital: Allergic interstitial nephritis.
Nafcillin in large doses can cause false-positive urine protein tests using sulfosalicylic acid method.
Drug: May antagonize hypoprothrombinemic effects of warfarin.
Absorption: Incompletely and erratically absorbed orally. Peak: 30–120 min IM; 15 min IV. Duration: 4 h PO; 4–6 h IM. Distribution: Distributes into CNS with inflamed meninges; crosses placenta; distributed into breast milk. Metabolism: Enters enterohepatic circulation. Elimination: Primarily excreted in bile; 10–30% excreted in urine. Half-Life: 1 h.
Assessment & Drug Effects
- Lab tests: Perform C&S prior to initiation of therapy and periodically thereafter. Obtain twice weekly differential WBC counts
in patients receiving IV nafcillin therapy for longer than 2 wk.
- Obtain a careful history before therapy to determine any prior allergic reactions to penicillins, cephalosporins, and other
allergens.
- Inspect IV site for inflammatory reaction. Also check IV site for leakage; in the older adult patient especially, loss of
tissue elasticity with aging may promote extravasation around the needle.
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Note: Allergic reactions, principally rash, occur most commonly. Nausea, vomiting, and diarrhea may occur with oral therapy.
- Monitor neutrophil count. Nafcillin-induced neutropenia (agranulocytosis) occurs commonly during third week of therapy. It
may be associated with malaise, fever, sore mouth, or throat. Perform periodic assessments of liver and kidney functions during
prolonged therapy.
- Be alert for signs of bacterial or fungal superinfections (see Appendix F) in patients on prolonged therapy.
- Determine IV sodium intake for patients with sodium restriction. Nafcillin sodium contains approximately 3 mEq of sodium per
gram.
Patient & Family Education
- Report promptly S&S of neutropenia (see Assessment & Drug Effects), superinfection, or hypokalemia (see Appendix F).
- Do not breast feed while taking this drug.
1%)
Canadian drug name; 
Prototype drug