Primaxin

Primaxin,

trademark for a broad-spectrum parenteral antibiotic (imipenem-cilastatin sodium).

---

imipenem and cilastatin sodium

Primaxin

Pharmacologic class: Carbapenem

Therapeutic class: Anti-infective

Pregnancy risk category C

Action

Acts against many gram-positive and gram-negative organisms by binding to bacterial cell wall, causing cell death. Addition of cilastatin prevents renal inactivation of imipenem, resulting in increased urinary concentration. Imipenem resists actions of many enzymes that degrade most other penicillins and penicillin-like drugs.

Availability

Powder for I.M. injection: 500 mg imipenem/500 mg cilastatin, 750 mg imipenem/750 mg cilastatin

Powder for I.V. injection: 250 mg imipenem/250 mg cilastatin, 500 mg imipenem/500 mg cilastatin

⊘Indications and dosages

➣ Lower respiratory tract infections, urinary tract infections, abdominal infections, gynecologic infections, skin infections, bone and joint infections, endocarditis, and polymicrobial infections

Adults: For mild infections, 250 to 500 mg I.V. q 6 hours; for moderate infections, 500 mg I.V. q 6 to 8 hours or 1 g I.V. q 8 hours; for serious infections, 500 mg I.V. q 6 hours to 1 g q 6 to 8 hours or 500 to 750 mg I.M. q 12 hours

Children: 15 to 25 mg/kg I.V. q 6 hours or 10 to 15 mg/kg I.M. q 6 hours

Infants ages 4 weeks to 3 months: 25 mg/kg I.V. q 6 hours

Infants ages 1 to 4 weeks: 25 mg/kg I.V. q 8 hours

Infants age 1 week and younger: 25 mg/kg I.V. q 12 hours

Dosage adjustment

• Renal impairment

Contraindications

• Hypersensitivity to drug, penicillins, or cephalosporins

Precautions

Use cautiously in:
• seizure disorders, renal impairment
• history of multiple hypersensitivity reactions
• elderly patients
• pregnant or breastfeeding patients.

Administration

• For I.V. use, reconstitute each 250- or 500-mg vial with 10 ml of diluent; shake well.
• For piggyback infusion, add 250- or 500-mg I.V. dose to 100 ml of diluent; shake solution until clear and drug has dissolved completely.
• Infuse doses of 500 mg or less over 20 to 30 minutes; infuse doses of 750 to 1,000 mg over 40 to 60 minutes.
• Slow infusion rate if patient experiences nausea, vomiting, dizziness or sweating.
• For I.M. use, inject into large muscle.

Route	Onset	Peak	Duration
I.V.	Rapid	End of infusion	6-8 hr
I.M.	Rapid	1-2 hr	12 hr

Adverse reactions

CNS: dizziness, drowsiness, seizures

CV: hypotension

GI: nausea, vomiting, diarrhea, pseudomembranous colitis

Hematologic: eosinophilia

Skin: rash, pruritus, diaphoresis, urticaria

Other: phlebitis at I.V. site, fever, superinfection, allergic reactions including anaphylaxis

Interactions

Drug-drug. Aminoglycosides: interference with imipenem effects

Cyclosporine, ganciclovir: increased risk of seizures

Probenecid: decreased renal excretion of imipenem

Drug-diagnostic tests. Alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase, bilirubin, blood urea nitrogen, creatinine, lactate dehydrogenase: increased values

Direct Coombs' test: positive result

Hematocrit, hemoglobin: decreased

Patient monitoring

☞ Stay alert for seizures in patients with brain lesions, head trauma, or other CNS disorders and in those receiving more than 2 g daily.
☞ Monitor closely for severe diarrhea and hypersensitivity reaction.
• Assess tissue or fluid culture results obtained before and during therapy.
• Monitor for signs and symptoms of infection, such as fever and elevated white blood cell count. Also evaluate for bacterial and fungal superinfection.
• Monitor electrolyte levels, especially sodium.

Patient teaching

• Caution patient to report discomfort at I.V. site.
☞ Instruct patient to report rash, hives, difficulty breathing, and signs or symptoms of superinfection (such as diarrhea, mouth sores, and vaginal itching or discharge).
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.