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Imipenem – Uses, Dosage, Side Effects, Interactions

Imipenem is a semisynthetic thienamycin that has a wide spectrum of antibacterial activity against gram-negative and gram-positive aerobic and anaerobic bacteria, including many multiresistant strains. It is stable to many beta-lactamases. Similar compounds include meropenem, known for having greater activity against Gram-negative bacteria, and the newer ertapenem which exhibits a longer half-life due to increased binding to plasma proteins.^[rx]Imipenem is commonly used in combination with cilastatin and is now available in a triple-drug product with cilastatin and sulbactam which was recently approved by the FDA. Imipenem was first approved by the FDA in November 1985 as the combination product Primaxin marketed by Merck & Co.^[rx]

Imipenem and cilastatin injection is used to treat certain serious infections that are caused by bacteria, including endocarditis (infection of the heart lining and valves) and respiratory tract (including pneumonia), urinary tract, abdominal (stomach area), gynecological, blood, skin, bone, and joint infections. Imipenem is in a class of medications called carbapenem antibiotics. It works by killing bacteria. Cilastatin is in a class of medications called dehydropeptidase inhibitors. It works by helping imipenem stay active in your body for a longer period of time.

Mechanism of action

Imipenem acts as an antimicrobial through the inhibition of cell wall synthesis of various gram-positive and gram-negative bacteria.^[rx] This inhibition of cell wall synthesis in gram-negative bateria is attained by binding to penicillin-binding proteins (PBPs). In E. coli and selected strains of P. aeruginosa, imipenem has shown to have the highest affinity to PBP-2, PBP-1a, and PBP-1b.^[rx] This inhibition of PBPs prevents the bacterial cell from adding to the peptidoglycan polymer which forms the bacterial cell wall eventually leading to cell death.^[rx]

Imipenem is a beta-lactam antibiotic belongings to the subgroup of carbapenems.^[rx] Imipenem is active against aerobic and anaerobic Gram-positive as well as Gram-negative bacteria including Pseudomonas aeruginosa and Enterococcus. It exerts a bactericidal effect by disrupting cell wall synthesis.

Indications of Imipenem

The spectrum of bacterial susceptibility and resistance

Acinetobacter anitratus, Acinetobacter calcoaceticus, Actinomyces odontolyticus, Aeromonas hydrophila, Bacteroides distasonis, Bacteroides uniformis, and Clostridium perfringens are generally susceptible to imipenem, while Acinetobacter baumannii, some Acinetobacter spp., Bacteroides fragilis, and Enterococcus faecalis have developed resistance to imipenem to varying degrees. Not many species are resistant to imipenem except Pseudomonas aeruginosa (Oman) and Stenotrophomonas maltophilia.^[rx]

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Coadministration with cilastatin

Imipenem is rapidly degraded by the renal enzyme dehydropeptidase 1 when administered alone, and is almost always coadministered with cilastatin to prevent this inactivation.^[rx]
Imipenem is indicated, in combination with cilastatin with or without sulbactam, for the treatment of bacterial infections including respiratory, skin, bone, gynecologic, urinary tract, and intra-abdominal as well as septicemia and endocarditis.^[rx]
Bloodstream Infections
Bone and Joint Infections
Complicated Intra-Abdominal Infections
Complicated Urinary Infection
Complicated Urinary Tract Infection
Endocarditis caused by staphylococcus aureus
Gynecological infection
Intra-Abdominal Infections
Lower respiratory tract infection bacterial
Pyelonephritis
Skin and Subcutaneous Tissue Bacterial Infections
Uncomplicated Urinary Tract Infections

Contraindications of Imipenem

Children less than 30 kg with renal impairment, children with CNS infections (increased seizure risk), known hypersensitivity to local anesthetics of the amide-type, and in patients with severe shock or heart block
History of seizures,
Concomitant ganciclovir; risk for generalized seizures,
Hypersensitivity to penicillins,
cephalosporins, and other beta-lactams

Dosage of Imipenem

Strengths: 500mg, 750mg

Intramuscular

500mg imipenem and 500mg cilastatin power mixture for intramuscular injection
750mg imipenem and 750mg cilastatin power mixture for intramuscular injection

Intravenous

250mg imipenem, 250mg cilastatin, and 10mg sodium bicarbonate power mixture for intravenous injection
500mg imipenem, 500mg cilastatin, and 20mg sodium bicarbonate power mixture for intravenous injection

Mild infections

(fully susceptible) 250 mg IV every 6 hr; (moderately susceptible including P. aeruginosa) 500 mg IV every 6 hr

Moderate infections

(fully susceptible) 500 mg IV every 6-8 hr; (moderately susceptible including P. aeruginosa) 500 mg IV every 6 hr or 1 g IV every 8 hr

Severe, life-threatening infections

(fully susceptible) 500 mg IV every 6 hr; (moderately susceptible including P. aeruginosa) 1 g IV every 8 hr or 1 g IV every 6 hr; maximum 50 mg/kg/day or 4 g/day, whichever is lower

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Cystic fibrosis

(12 years and older) up to 90 mg/kg/day IV divided every 6 hr; maximum 4 g/day

Urinary tract infections, uncomplicated

250 mg IV every 6 hr

Urinary tract infections, complicated

500 mg IV every 6 hr

Gynecologic infections

500-750 mg IM every 12 hr

Intra-abdominal infections

750 mg IM every 12 hr

Lower respiratory tract infections

500-750 mg IM every 12 hr

Skin/skin structure infections

500-750 mg IM every 12 hr

Side Effects of Imipenem

Most Common

pain, swelling, redness, bruising, or hardening where the medicine was injected;
nausea
vomiting
diarrhea
confusion
drooping eyelids
seizures
headache
redness, pain, or swelling at the injection site

Common

severe diarrhea (watery or bloody stools) that may occur with or without fever and stomach cramps (may occur up to 2 months or more after your treatment)
hives
itching
rash
difficulty breathing or swallowing
blisters on the skin, mouth, nose, and eyes
sloughing (shedding) of skin
confusion
seizures

Rare

severe stomach pain, diarrhea that is watery or bloody;
upper stomach pain, loss of appetite;
jaundice (yellowing of the skin or eyes);
a seizure (convulsions);
fever; or
a light-headed feeling, like you might pass out.
dizziness, drowsiness;
nausea, vomiting, diarrhea; or
itching, rash.

Imipenem and cilastatin injection may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.

Drug Interactions of Imipenem

amifampridine
aminophylline
anisindione
bcg
bupropion
cholera vaccine, live
cyclosporine
dicumarol
divalproex sodium
dyphylline
entecavir
estradiol
ethinyl estradiol
evening primrose
fluphenazine
ganciclovir
ginkgo
indium oxyquinoline in-111
iohexol
iopamidol
lindane topical
metrizamide
mycophenolate mofetil
mycophenolic acid
oxtriphylline
pemetrexed
polyethylene glycol 3350 with electrolytes
probenecid
theophylline
tramadol
typhoid vaccine, live
valganciclovir
valproic acid
warfarin

Pregnancy

Category C: Risk unknown. Human studies are inadequate.

Before using imipenem and cilastatin injection,

tell your doctor and pharmacist if you are allergic to imipenem or cilastatin; other carbapenem antibiotics such as doripenem (Doribax), ertapenem (Invanz), or meropenem (Merrem); local anesthetics such as bupivacaine (Exparel, Marcaine, Sensorcaine), etidocaine (Duranest), lidocaine, mepivacaine (Carbocaine, Prolocaine), or prilocaine (Citanest); cephalosporins such as cefaclor (Ceclor), cefadroxil (Duricef), or cephalexin (Keflex); other beta-lactam antibiotics such as penicillin or amoxicillin (Amoxil, Trimox, Wymox); any other medications; or any of the ingredients in imipenem and cilastatin injection. Ask your pharmacist or check the manufacturer’s patient information for a list of the ingredients.
tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention any of the following: ganciclovir, probenecid (Probalan), or valproic acid (Depakene, Depakote). Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
tell your doctor if you have or have ever brain lesions, seizures, or kidney disease.
tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding. If you become pregnant while using imipenem and cilastatin injection, call your doctor.

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References