oxacillin sodium
Bactocill

Available forms
Available by prescription only
Capsules: 250 mg, 500 mg
Injection: 250 mg, 500 mg, 1 g, 2 g, 4 g, 10 g
I.V. infusion: 1 g, 2 g, 4 g
Oral solution: 250 mg/5 ml (after reconstitution)

Indications and dosages
 Systemic infections caused by Staphylococcus aureus. Adults and children who weigh more than 40 kg (88 lb): 500 mg P.O. q 4 to 6 hours for mild to moderate infections. Dose is 1 g P.O. q 4 to 6 hours when changing from I.V. to P.O. therapy. Or, 250 to 500 mg I.M. or I.V. q 4 to 6 hours. For more severe infections, 1 g or more I.V. or I.M. q 4 to 6 hours. Serious infections are treated for 1 to 2 weeks.
Children older than age 1 month who weigh less than 40 kg: 50 to 100 mg/kg P.O. daily, divided into doses given q 4 to 6 hours. Or, 50 to 200 mg/kg I.M. or I.V. daily, divided into doses given q 4 to 6 hours. Doses vary based on severity of infection.
 Acute or chronic osteomyelitis caused by susceptible organisms. Adults: 1.5 to 2 g I.V. q 4 hours for 4 to 8 weeks or I.V. dose for 5 to 28 days followed by P.O. dose for 3 to 6 weeks for a total of 6 weeks of therapy.
 Treatment of native valve endocarditis caused by methicillin-susceptible staphylococci. Adults: 2 g I.V. q 4 hours for 4 to 6 weeks with gentamicin for the first 3 to 5 days.
 Treatment of prosthetic valve endocarditis caused by methicillin-susceptible staphylococci. Adults: 2 g I.V. q 4 hours for 6 weeks or longer with gentamicin and rifampin.
≡ Dosage adjustment. For adults with creatinine clearance less than 10 ml/minute, 1 g I.M. or I.V. q 4 to 6 hours.

Pharmacodynamics
Antibiotic action: Oxacillin is bactericidal; it adheres to bacterial penicillin-binding proteins, thus inhibiting bacterial cell wall synthesis. Oxacillin resists the effects of penicillinases-enzymes that inactivate penicillin-and is thus active against many strains of penicillinase-producing bacteria; this activity is most important against penicillinase-producing staphylococci; some strains may remain resistant. Oxacillin is also active against a few gram-positive aerobic and anaerobic bacilli but has no significant effect on gram-negative bacilli.

Pharmacokinetics
Absorption: Absorbed rapidly but incompletely from the GI tract; stable in an acid environment. Food decreases absorption.
Distribution: Distributed widely. CSF penetration is poor but enhanced by meningeal inflammation. Oxacillin crosses the placental barrier, and is 89% to 94% protein-bound.
Metabolism: Metabolized partially.
Excretion: Excreted primarily in urine by renal tubular secretion and glomerular filtration; it also appears in breast milk and in small amounts in bile. Elimination half-life in adults is 1/2 to 1 hour, extended to 2 hours in severe renal impairment. Dosage adjustments aren’t required in patients with creatinine clearance less than 10 ml/minute.

Contraindications and precautions
Contraindicated in patients hypersensitive to drug or other penicillins. Use cautiously in neonates, infants, and patients with other drug allergies, especially to cephalosporins.

Interactions
Drug-drug. Aminoglycosides: Produces synergistic bactericidal effects against S. aureus. This is a therapeutic effect.
Probenecid: Blocks renal tubular secretion of penicillins, increasing their serum levels. Use together cautiously.
Drug-food. Any food: Decreases absorption. Tell patient to take drug on an empty stomach.
Carbonated beverages, fruit juice: Interferes with absorption. Tell patient to take drug with water.

Adverse reactions
CNS: neuropathy, neuromuscular irritability, seizures, lethargy, hallucinations, anxiety, confusion, agitation, depression, dizziness, fatigue.
GI: oral lesions, nausea, vomiting, diarrhea, enterocolitis, pseudomembranous colitis.
GU: interstitial nephritis, nephropathy.
Hematologic: thrombocytopenia, eosinophilia, hemolytic anemia, neutropenia, anemia, agranulocytosis.
Other: hypersensitivity reactions (fever, chills, rash, urticaria, anaphylaxis, overgrowth of nonsusceptible organisms, thrombophlebitis).

Effects on lab test results
• May increase ALT, AST, alkaline phosphatase, and LDH levels.
• May increase eosinophil count. May decrease hemoglobin, hematocrit, and platelet, neutrophil, and granulocyte counts.

Overdose and treatment
Overdose may cause neuromuscular sensitivity or seizures.
 There are no specific recommendations. Treatment is supportive. After recent ingestion (within 4 hours), empty the stomach by induced emesis or gastric lavage; follow with activated charcoal to reduce absorption. Oxacillin isn’t appreciably removed by peritoneal dialysis or hemodialysis.

Special considerations
• Give oral drug with water; acid in fruit juice or carbonated beverage may inactivate drug.
• Give oral dose on empty stomach; food decreases absorption.
• Except in osteomyelitis, don’t give by I.M. or I.V. route unless patient can’t take oral dose.
• For oral preparation, add amount of water specified on bottle to yield 250 mg/5 ml. Add water in 2 parts and shake vigorously.
• For I.M. preparation, add 1.4, 2.8, 5.7, 11.4, or 21.8 ml of sterile water for injection or half-normal or normal saline solution injection to vial containing 250 mg, 500 mg, 1 g, 2 g, or 4 g, respectively. Final solution is 250 mg/1.5 ml.
• For intermittent I.V. injection, use sterile water for injection or normal saline solution injection; add 5 ml to 250-mg vial to equal 50 mg/ml. Add 5 ml, 10 ml, 20 ml, or 40 ml to vials containing 500 mg, 1 g, 2 g, or 4 g, respectively, and 93 ml to 10-g pharmacy bulk package to produce 100 mg/ml. Inject slowly over 10 minutes. For continuous I.V. infusion, further dilute with compatible solution to 0.5 to 40 mg/ml. Infuse over 30 to 60 minutes. Drug loses 10% of potency within 6 hours of dilution.
• Thaw commercial solutions at room temperature or in refrigerator.
• Oxacillin is incompatible with aminoglycosides in the same I.V. infusion.
• Prosthetic valve endocarditis caused by coagulase-negative staphylococci is usually methicillin-resistant.
• When drug is given for group A beta-hemolytic streptococci, continue therapy for at least 10 days to decrease risk of glomerulonephritis and rheumatic fever.
• Oxacillin alters tests for urinary and serum proteins; turbidimetric urine and serum proteins are often falsely positive or elevated in tests using sulfosalicylic acid or trichloroacetic acid.
• Oxacillin may falsely decrease serum aminoglycoside levels.
Breast-feeding patients
• Oxacillin appears in breast milk. Use cautiously in breast-feeding women.
Pediatric patients
• Elimination of oxacillin is reduced in neonates. Transient hematuria, azotemia, and albuminuria have occurred in some neonates receiving oxacillin. Monitor renal function closely.
Geriatric patients
• Half-life of drug may be prolonged in elderly patients because of impaired renal function.
• These patients have an increased risk of thrombophlebitis during I.V. infusion.

Patient education
• Explain need to take oral preparations without food and to follow with water only, not fruit juice or carbonated beverages.
• Tell patient to report allergic reactions or severe diarrhea promptly.
• Emphasize importance of completing the full course of therapy.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use