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Primaxin IM Dosage

Medically reviewed by Last updated on Jan 26, 2022.

Generic name: IMIPENEM 500mg in 2mL, CILASTATIN SODIUM 500mg in 2mL
Dosage form: injection, powder, for suspension

PRIMAXIN I.M. is for intramuscular use only.

The dosage recommendations for PRIMAXIN I.M. represent the quantity of imipenem to be administered. An equivalent amount of cilastatin is also present.

Patients with lower respiratory tract infections, skin and skin structure infections, and gynecologic infections of mild to moderate severity may be treated with 500 mg or 750 mg administered every 12 hours depending on the severity of the infection.

Intra-abdominal infection may be treated with 750 mg every 12 hours. [See table below.]


Type*/Location of Infection


Dosage Regimen


Lower respiratory tract

Skin and skin structure



500 or 750 mg q 12 h depending on the severity of infection



750 mg q 12 h

Total daily IM dosages greater than 1500 mg per day are not recommended.

The dosage for any particular patient should be based on the location of and severity of the infection, the susceptibility of the infecting pathogen(s), and renal function.

The duration of therapy depends upon the type and severity of the infection. Generally, PRIMAXIN I.M. should be continued for at least two days after the signs and symptoms of infection have resolved. Safety and efficacy of treatment beyond fourteen days have not been established.

PRIMAXIN I.M. should be administered by deep intramuscular injection into a large muscle mass (such as the gluteal muscles or lateral part of the thigh) with a 21 gauge 2” needle. Aspiration is necessary to avoid inadvertent injection into a blood vessel.


The safety and efficacy of PRIMAXIN I.M. have not been studied in patients with creatinine clearance of less than 20 mL/min/1.73 m2. Serum creatinine alone may not be a sufficiently accurate measure of renal function. Creatinine clearance (Tcc) may be estimated from the following equation:

Tcc (Males) = (wt. in kg) (140–age)
(72) (creatinine in mg/dL)

Tcc (Females) = 0.85 x above value


PRIMAXIN I.M. should be prepared for use with 1.0% lidocaine HCl solution1 (without epinephrine). PRIMAXIN I.M. 500 should be prepared with 2 mL and PRIMAXIN I.M. 750 with 3 mL of lidocaine HCl. Agitate to form a suspension, then withdraw and inject the entire contents of vial intramuscularly. The suspension of PRIMAXIN I.M. in lidocaine HCl should be used within one hour after preparation. Note: The IM formulation is not for IV use.


Refer to the package circular for lidocaine HCl for detailed information concerning CONTRAINDICATIONS, WARNINGS, PRECAUTIONS, and ADVERSE REACTIONS.


Before Reconstitution

The dry powder should be stored at a temperature below 25°C (77°F).

Suspensions for IM Administration

Suspensions of PRIMAXIN I.M. are white to light tan in color. Variations of color within this range do not affect the potency of the product.

The suspension of PRIMAXIN I.M. in lidocaine HCl should be used within one hour after preparation.

PRIMAXIN I.M. should not be mixed with or physically added to other antibiotics. However, PRIMAXIN I.M. may be administered concomitantly but at separate sites with other antibiotics, such as aminoglycosides.

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Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.