Imipenem/Cilastatin (Premaxin®) for Dogs and Cats

Overview of Imipenem/Cilastatin for Dogs and Cats

Imipenem with cilastatin, also known as Premaxin®, acts as an effective antibiotic in dogs and cats for the treatment of infections of various body systems. It most valuable for treatment of mixed aerobic and anaerobic infections; bacteremia in non-neutropenic patients; and serious nosocomial infections.

• Imipenem can be further described as a semi-synthetic thienamycin that is administered intravenously or intramuscularly in combination with cilastatin to reduce toxicity.
• Cilastatin, a renal dipeptidase inhibitor, inhibits the enzymatic breakdown of imipenem and increases urinary excretion of the active drug.
• Imipenem preferentially binds to bacterial penicillin-binding protein sites and inhibits bacterial cell wall peptidoglycan synthesis. It has a wide spectrum of antibacterial activity against Gram-negative and Gram-positive aerobic and anaerobic bacteria. It is also effective against some multiresistant strains of bacteria. Imipenem is also effective against bacteria that produce beta-lactamases.
• Imipenum should be reserved for treatment of organisms that are resistant to the usual antibiotics.
• Imipenem/cilastatin is a prescription drug and can only be obtained from a veterinarian or by prescription from a veterinarian.
• This drug is not approved for use in animals by the Food and Drug Administration but it is prescribed legally by veterinarians as an extra-label drug.

Brand Names and Other Names Imipenem/Cilastatin

• This drug is registered for use in humans only.
• Human formulations: Premaxin® (Merck)
• Veterinary formulations: None

Uses of Imipenem/Cilastatin for Dogs and Cats

Uses may include treatment of the following:

• Lower respiratory tract infections
• Urogenital tract infections
• Dermatogical infections
• Infections of bone and joint
• Endocarditis
• Intra-abdominal infections
• Bacterial septicemia
• Infections resistant to aminoglycosides, cephalosporins, or penicillins

Precautions and Side Effects

• While generally safe and effective when prescribed by a veterinarian, imipenem/cilastatin can cause side effects in some animals.
• Imipenem should not be used in animals with known hypersensitivity or allergy to the drug or other beta-lactams.
• The safety of imipenem/cilastatin has not been established for animals that are pregnant or lactating.
• Side effects may include: nausea, vomiting, diarrhea, skin rashes, phlebitis, eosinophilia, transient elevation of liver function tests and seizures (esp. in patients with CNS dysfunction and renal failure).
• Imipenem should be used with caution in patients with impaired renal function: Its dose must be adjusted in renal failure.
• Also, high doses of imipenem have been associated with CNS side effects, including confusion, muscle twitching, and seizures. Imipenem should not be used in very young patients with CNS infections because of a risk of inducing seizures.
• It is recommended that renal, hepatic, and hemopoietic function be monitored during prolonged treatment with imipenem.

Drug Interactions

Imipenem/cilastatin may interact with other medications. Consult with your veterinarian to determine if other drugs your dog or cat is receiving could interact with imipenem/cilastatin. Such drugs may include:

• Impenem should not be physically mixed with other antibiotics. It is contraindicated in patients allergic to local anesthetics of the amide type and use in clients with heart block (because of lidocaine diluent) or in patients in severe shock.
• It interacts with cyclosporine, causing increased CNS side effects of both drugs.
• When it is used with ganciclovir there is an increased risk of seizures. Probenecid increases imipenem blood levels and its half-life; these drugs should not be administered together.

How Imipenem is Supplied

• The injectable forms include powder for IV injection and powder for IM injection contain imipenem, 250 mg and cilastatin 250 mg; imipenem 500 mg, and cilastatin 500 mg; or imipenem, 750 mg and cilastatin 750 mg concentrations.

Dosing Information of Imipenem/Cilastatin for Dogs and Cats

• Medication should never be administered without first consulting your veterinarian.
• The dosage prescribed may vary depending on the reason for prescribing.
• The duration of administration depends on the condition being treated, response to the medication and the development of any adverse effects.
• In dogs and cats, the usual dose of Imipenem with cilastatin is 2.5 to 5 mg per pound (5 to 10 mg/kg) every 6 to 8 hours intravenously. Doses as high as 5 mg per pound (10 mg/kg) every 8 hours have been recommended.