Source: FDA, National Drug Code (US) Revision Year: 2022
Imipenem and Cilastatin for Injection (I.V.) is a combination of imipenem and cilastatin. Imipenem is a penem antibacterial drug [see Microbiology (12.4)]. Cilastatin sodium is a renal dehydropeptidase inhibitor that limits the renal metabolism of imipenem.
Intravenous infusion of Imipenem and Cilastatin for Injection (I.V.) over 20 minutes results in peak plasma levels of imipenem antimicrobial activity that range from 21 to 58 mcg/mL for the 500 mg dose, and from 41 to 83 mcg/mL for the 1,000 mg dose. At these doses, plasma levels of imipenem antimicrobial activity decline to below 1 mcg/mL or less in 4 to 6 hours. Peak plasma levels of cilastatin following a 20-minute intravenous infusion of Imipenem and Cilastatin for Injection (I.V.) range from 31 to 49 mcg/mL for the 500 mg dose, and from 56 to 88 mcg/mL for the 1,000 mg dose.
The binding of imipenem to human serum proteins is approximately 20% and that of cilastatin is approximately 40%.
Imipenem has been shown to penetrate into human tissues, including vitreous humor, aqueous humor, lung, peritoneal fluid, CSF, bone, interstitial fluid, skin, and fascia. As there are no adequate and well-controlled studies of imipenem treatment in these additional body sites, the clinical significance of these tissue concentration data is unknown.
After a 1 gram dose of Imipenem and Cilastatin for Injection (I.V.), the following average levels of imipenem were measured (usually at 1 hour post dose except where indicated) in the tissues and fluids listed in Table 9:
Table 9. Average Levels of Imipenem:
| Tissue or Fluid | N | Imipenem Level mcg/mL or mcg/g | Range |
|---|---|---|---|
| Vitreous Humor | 3 | 3.4 (3.5 hours post dose) | 2.88 to 3.6 |
| Aqueous Humor | 5 | 2.99 (2 hours post dose) | 2.4 to 3.9 |
| Lung Tissue | 8 | 5.6 (median) | 3.5 to 15.5 |
| Sputum | 1 | 2.1 | — |
| Pleural | 1 | 22 | — |
| Peritoneal | 12 | 23.9 S.D.±5.3 (2 hours post dose) | — |
| Bile | 2 | 5.3 (2.25 hours post dose) | 4.6 to 6 |
| CSF (uninflamed) | 5 | 1 (4 hours post dose) | 0.26 to 2 |
| CSF (inflamed) | 7 | 2.6 (2 hours post dose) | 0.5 to 5.5 |
| Fallopian Tubes | 1 | 13.6 | — |
| Endometrium | 1 | 11.1 | — |
| Myometrium | 1 | 5 | — |
| Bone | 10 | 2.6 | 0.4 to 5.4 |
| Interstitial Fluid | 12 | 16.4 | 10 to 22.6 |
| Skin | 12 | 4.4 | NA |
| Fascia | 12 | 4.4 | NA |
Imipenem, when administered alone, is metabolized in the kidneys by dehydropeptidase I, resulting in relatively low levels in urine. Cilastatin an inhibitor of this enzyme, effectively prevents renal metabolism of imipenem so that when imipenem and cilastatin sodium are given concomitantly, adequate antibacterial levels of imipenem are achieved in the urine.
The plasma half-life of each component is approximately 1 hour. Approximately 70% of the administered imipenem is recovered in the urine within 10 hours after which no further urinary excretion is detectable. Urine concentrations of imipenem in excess of 10 mcg/mL can be maintained for up to 8 hours with Imipenem and Cilastatin for Injection (I.V.) at the 500-mg dose. Approximately 70% of the cilastatin sodium dose is recovered in the urine within 10 hours of administration of Imipenem and Cilastatin for Injection (I.V.). Imipenem/cilastatin sodium is hemodialyzable [see Overdosage (10)].
No accumulation of imipenem/cilastatin in plasma or urine is observed with regimens administered as frequently as every 6 hours in patients with normal renal function.
In healthy elderly volunteers (65 to 75 years of age with normal renal function for their age), the pharmacokinetics of a single dose of imipenem 500 mg and cilastatin 500 mg administered intravenously over 20 minutes are consistent with those expected in subjects with slight renal impairment for which no dosage alteration is considered necessary. The mean plasma half-lives of imipenem and cilastatin are 91 ± 7 minutes and 69 ± 15 minutes, respectively. Multiple dosing has no effect on the pharmacokinetics of either imipenem or cilastatin, and no accumulation of imipenem/cilastatin is observed.
Doses of 25 mg/kg/dose in patients 3 months to <3 years of age, and 15 mg/kg/dose in patients 3 to 12 years of age were associated with mean trough plasma concentrations of imipenem of 1.1±0.4 mcg/mL and 0.6±0.2 mcg/mL following multiple 60-minute infusions, respectively; trough urinary concentrations of imipenem were in excess of 10 mcg/mL for both doses. These doses have provided adequate plasma and urine concentrations for the treatment of non-CNS infections.
In a dose-ranging study of smaller premature infants (670 to 1,890 g) in the first week of life, a dose of 20 mg/kg q12h by 15 to 30 minutes infusion was associated with mean peak and trough plasma imipenem concentrations of 43 mcg/mL and 1.7 mcg/mL after multiple doses, respectively. However, moderate accumulation of cilastatin in neonates may occur following multiple doses of Imipenem and Cilastatin for Injection (I.V.). The safety of this accumulation is unknown.
Imipenem and Cilastatin for Injection (I.V.) is a combination of imipenem and cilastatin. The bactericidal activity of imipenem results from the inhibition of cell wall synthesis. Its greatest affinity is for penicillin binding proteins (PBPs) 1A, 1B, 2, 4, 5 and 6 of Escherichia coli, and 1A, 1B, 2, 4 and 5 of Pseudomonas aeruginosa. The lethal effect is related to binding to PBP 2 and PBP 1B.
Imipenem has a high degree of stability in the presence of beta-lactamases, both penicillinases and cephalosporinases produced by Gram-negative and Gram-positive bacteria. It is a potent inhibitor of beta-lactamases from certain Gram-negative bacteria which are inherently resistant to most beta-lactam antibacterials, e.g., Pseudomonas aeruginosa, Serratia spp., and Enterobacter spp.
Imipenem is inactive in vitro against Enterococcus faecium, Stenotrophomonas maltophilia and some isolates of Burkholderia cepacia. Methicillin-resistant staphylococci should be reported as resistant to imipenem.
In vitro tests show imipenem to act synergistically with aminoglycoside antibacterials against some isolates of Pseudomonas aeruginosa.
Imipenem has been shown to be active against most isolates of the following microorganisms, both in vitro and in clinical infections [see Indications and Usage (1)].
Gram-positive bacteria:
Enterococcus faecalis
Staphylococcus aureus
Staphylococcus epidermidis
Streptococcus agalactiae (Group B streptococci)
Streptococcus pneumoniae
Streptococcus pyogenes
Gram-negative bacteria:
Acinetobacter spp.
Citrobacter spp.
Enterobacter spp.
Escherichia coli
Gardnerella vaginalis
Haemophilus influenzae
Haemophilus parainfluenzae
Klebsiella spp.
Morganella morganii
Proteus vulgaris
Providencia rettgeri
Pseudomonas aeruginosa
Serratia spp., including S. marcescens
Gram positive bacteria:
Bifidobacterium spp.
Clostridium spp.
Eubacterium spp.
Peptococcus spp.
Peptostreptococcus spp.
Propionibacterium spp.
Gram-negative bacteria:
Bacteroides spp. , including B. fragilis
Fusobacterium spp.
The following in vitro data are available, but their clinical significance is unknown. At least 90 percent of the following bacteria exhibit an in vitro minimum inhibitory concentration (MIC) less than or equal to the susceptible breakpoint for imipenem against isolates of similar genus or organism group. However, the efficacy of imipenem in treating clinical infections due to these bacteria has not been established in adequate and well-controlled clinical trials.
Gram-positive bacteria:
Bacillus spp.
Listeria monocytogenes
Nocardia spp.
Staphylococcus saprophyticus
Group C streptococci
Group G streptococci
Viridans group streptococci
Gram-negative bacteria:
Aeromonas hydrophila
Alcaligenes spp.
Capnocytophaga spp.
Haemophilus ducreyi
Neisseria gonorrhoeae
Pasteurella spp.
Providencia stuartii
Anaerobic bacteria:
Prevotella bivia
Prevotella disiens
Prevotella melaninogenica
Veillonella spp.
For specific information regarding susceptibility test methods, interpretive criteria, and associated test methods and quality control standards recognized by FDA for this drug, please see: https://www.fda.gov/STIC.
Long term studies in animals have not been performed to evaluate carcinogenic potential of imipenem/cilastatin. A variety of bacterial and mammalian tests were performed to evaluate genetic toxicity. The tests used were: V79 mammalian cell mutagenesis assay (cilastatin sodium alone and imipenem alone), Ames test (cilastatin sodium alone and imipenem alone), unscheduled DNA synthesis assay (imipenem/cilastatin sodium) and in vivo mouse cytogenetics test (imipenem/cilastatin sodium). None of these tests showed any evidence of genetic alterations.
Impairment of fertility or reproductive performance was not observed in male and female rats given imipenem/cilastatin at intravenous doses up to 80 mg/kg/day and at a subcutaneous dose of 320 mg/kg/day. In rats, a dose of 320 mg/kg/day was approximately equal to the highest recommended human dose based on body surface area.
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