β-lactam antibiotic; bacerial cell wall synthesis

The in vitro activity of N-formimidoyl thienamycin (MK0787), a stable congener of thienamycin, was determined against 200 species of aerobic and 84 species of anaerobic bacteria. The compound was highly active against resistant gram-negative bacilli, penicillin-resistant Staphylococcus aureus, enterococci, and anaerobic bacteria. The new derivative of thienamycin was more active than the parent compound, probably reflecting the stability of the analog[2].

Time-dependent death is the effect of imipenem (MK0787) (4 mg/kg, 8 mg/kg, 16 mg/kg, 32 mg/kg, 64 mg/kg, IP, single dose) [3]. Ipenem's pharmacokinetic properties (4 mg/kg, 8 mg/kg, 16 mg/kg, 32 mg/kg, 64 mg/kg, IP,single) in a neutropenic mouse biofilm lung infection model[1]. 50 Drugs and dosage (mg/kg) Cmax (mg/L) Tmax (min) AUCtot (mg·min/L) Vz/F (ml/kg) Vss/F (ml/kg) CL/F (ml/min ) /kg) t1/2(min) MRT(min) Imipenem8 15 (7.1) 21 (11) 1,470 (777) 648 (330) 721 (343) 6.7 (3) 67 (11) 108 (12) 16 34 (6) 28 (18) 2,857 (559) 507 (140) 543 (121) 5.8 (1) 60 (9.1) 94 (10) 32 54 (11) 18 (6.1) 4,895 (635) 516 (75 ) 566 (83) 6.6 (0.8) 54 (6.5) 86 (11) 64 69 (37) 15 (9.5) 6,037 (2,976) 547 (274) 617 (308) 7.4 (3.6) 43 (22) 70 (35 ).

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Many Pseudomonas aeruginosa isolates from the airways of patients with cystic fibrosis (CF) are sensitive to antibiotics in susceptibility testing, but eradication of the infection is difficult. The main reason is the biofilm formation in the airways of patients with CF. The pharmacokinetics (PKs) and pharmacodynamics (PDs) of antimicrobials can reliably be used to predict whether antimicrobial regimens will achieve the maximum bactericidal effect against infections. Unfortunately, however, most PK/PD studies of antimicrobials have been done on planktonic cells and very few PK/PD studies have been done on biofilms, partly due to the lack of suitable models in vivo. In the present study, a biofilm lung infection model was developed to provide an objective and quantitative evaluation of the PK/PD profile of antimicrobials. Killing curves were set up to detect the antimicrobial kinetics on planktonic and biofilm P. aeruginosa cells in vivo. Colistin showed concentration-dependent killing, while imipenem showed time-dependent killing on both planktonic and biofilm P. aeruginosa cells in vivo. The parameter best correlated to the elimination of bacteria in lung by colistin was the area under the curve (AUC) versus MIC (AUC/MIC) for planktonic cells or the AUC versus minimal biofilm inhibitory concentration (MBIC; AUC/MBIC) for biofilm cells. The best-correlated parameter for imipenem was the time that the drug concentration was above the MIC for planktonic cells (T(MIC)) or time that the drug concentration was above the MBIC (T(MBIC)) for biofilm cells. However, the AUC/MIC of imipenem showed a better correlation with the efficacy of imipenem for biofilm infections (R(2) = 0.89) than planktonic cell infections (R(2) = 0.38). The postantibiotic effect (PAE) of colistin and imipenem was shorter in biofilm infections than planktonic cell infections in this model[3].

Wild-type P. aeruginosa PAO1 was used in this study. Colistin and imipenem were pharmaceutical grade. The MIC was detected by Etest and by a microtiter method; the minimal bactericidal concentration (MBC) for planktonic cells was detected by the microtiter method. The MICs and MBCs of colistin for PAO1 were 2 to 4 mg/liter and 8 mg/liter, respectively; the MICs and MBCs of imipenem were 1 mg/liter and 4 mg/liter, respectively. The minimal biofilm inhibitory concentration (MBIC) and minimal biofilm eradication concentration (MBEC) of colistin and imipenem were determined by use of a modified Calgary biofilm device as previously reported. In short, the biofilms are formed on pegs, treated by antibiotics, and detached by sonication for the assessment of bacterial killing. The MBIC and MBEC of colistin were 8 mg/liter and 64 mg/liter, respectively; the MBIC and MBEC of imipenem were 8 mg/liter and 128 mg/liter, respectively[3].

Animal/Disease Models: Neutropenic biofilm lung infection mouse model [3]
Doses: 4 mg/kg, 8 mg/kg, 16 mg/kg, 32 mg/kg, 64 mg/kg
Doses: 4 mg/kg, 8 mg/kg, 16 mg/kg kg, 32 mg/kg, 64 mg/kg, IP, single
Doses: Demonstrates time-dependent killing of mice infected with biofilm bacterial lungs effect.

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PKs of colistin and imipenem.[3]
While the infected animals were under anesthesia, they were treated intraperitoneally 2 h after infection with 0.2 ml of different doses of colistin (16 mg/kg, 64 mg/kg, 256 mg/kg; 6 mice/regimen; total, 18 mice) or imipenem (4 mg/kg, 8 mg/kg, 16 mg/kg, 32 mg/kg, 64 mg/kg; 6 mice/regimen; total, 30 mice) as a single administration. The control groups received equal volumes of 0.15 M NaCl intraperitoneally. An approximately 0.08-ml blood sample was collected from the tail at 5 min, 15 min, 30 min, 60 min, 120 min, 180 min, and 240 min after antibiotic administration. At the end of the experiment, the mice were euthanized with pentobarbital/lidocaine. Blood samples were centrifuged at 3,000 rpm, and serum was collected for measurement of antibiotic concentration by a biologic method (agar diffusion), as reported previously, employing Streptococcus sp. strain EB68 (imipenem) or Bordetella bronchiseptica ATCC 4617 (colistin). The detection limits were 1 μg/ml (colistin) and 0.2 μg/ml (imipenem). Data about the variability of the assay are presented in the supplementary material. Time-concentration curves of colistin and imipenem were established.

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Time-kill study of colistin and imipenem in planktonic and biofilm bacteria and PAE.[3]
To establish killing curves of colistin and imipenem, anesthetized neutropenic mice infected with planktonic bacteria (4 mice/point; total, 176 mice) or biofilm bacteria (4 mice/point; total, 176 mice) were treated at 2 h after infection with a single intraperitoneal dose of colistin or imipenem (4× MIC, 16× MIC, and 64× MIC; 4 to 256 mg/kg). Control mice received the same volume of saline. The mice were euthanized, and lungs were collected aseptically at −2, 0, 2, 4, 8, 12, and 24 h after bacterial challenge and homogenized in 5 ml of sterilized saline. Humane endpoints were applied during the period. The numbers of CFU were counted for plotting of the killing curves. The duration of the postantibiotic effect (PAE) was calculated by the formula T − C, where T is the time required for the mean count of CFU in the lung of treated mice to increase by 1 log10 unit above its value at the time that the antibiotic concentration in serum fell below the MIC or MBIC, and C is the time required for the mean count of CFU in the lungs of control mice to increase by 1 log unit above the viable count at time zero.

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PK/PD indices of colistin and imipenem in planktonic and biofilm bacteria in vivo.[3]
To establish PK/PD indices of colistin and imipenem, anesthetized neutropenic mice infected with planktonic bacteria (total, 60 mice) or biofilm bacteria (total, 60 mice) were treated from the time point of 2 h after infection with multiple intraperitoneal doses of colistin (range, 16 to 256 mg/kg, representing 2× MBIC to 32× MBIC/4× MBEC) or imipenem (range, 8 to 64 mg/kg, representing 1× MBIC to 8× MBIC). Due to the toxicity of imipenem, it was not possible to administer higher dosages. The multiple dosages were administered at time intervals ranging from 2 h to 16 h after infection for periods of 12 h (colistin) and 24 h (imipenem). The mice were euthanized, and lungs were collected at the end of the experiment and homogenized in 5 ml of sterilized saline. The numbers of CFU were counted for each lung and expressed as the log10 number of CFU per lung. The counts of viable bacteria for each regimen were plotted with the PK parameters.

Absorption, Distribution and Excretion
Imipenem is not effectively absorbed from the gastrointestinal tract and therefore must be administered parenterally. The bioavailability of the IM injection is 89%.
Approximately 70% of imipenem is excreted in the urine as the parent drug.
The reported volume of distribution for imipenem ranges from 0.23-0.31 L/kg.
The total clearance of imipenem is 0.2 L/h/kg. When used alone, the renal clearance is 0.05 L/h/kg. In combination with cilastatin the renal clearance of imipenem is 0.15 L/h/kg, likely due to the increased concentration of the parent drug.

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Metabolism / Metabolites
Imipenem is metabolized by renal dehydropeptidase.
Renal.
Half Life: 1 hour

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Biological Half-Life
When given via IV injection imipenem has a half-life of 1 h. The apparent half-life of the IM injection ranges from 1.3-5.1 h, likely due to slower absorption form the injection site.

Protein Binding
Imipenem is 20% bound to plasma proteins.

[1]. Johann Motsch, et al. RESTORE-IMI 1: A Multicenter, Randomized, Double-blind Trial Comparing Efficacy and Safety of Imipenem/Relebactam vs Colistin Plus Imipenem in Patients With Imipenem-nonsusceptible Bacterial Infections. Clin Infect Dis. 2020 Apr 15;70(9):1799-1808.
[2]. F P Tally, et al. In vitro activity of N-formimidoyl thienamycin (MK0787). Antimicrob Agents Chemother. 1980 Oct;18(4):642-4.
[3]. Wang Hengzhuang, et al. In vivo pharmacokinetics/pharmacodynamics of colistin and imipenem in Pseudomonas aeruginosa biofilm infection. Antimicrob Agents Chemother. 2012 May;56(5):2683-90.

Imipenem is a broad-spectrum, intravenous beta-lactam antibiotic of the carbapenem subgroup. It has a role as an antibacterial drug. It is a beta-lactam antibiotic allergen and a member of carbapenems. It is a tautomer of an imipenem zwitterion.
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. Imipenem is commonly used in combination with [cilastatin] and is now available in a triple-drug product with cilastatin and [relebactam] 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.
Imipenem anhydrous is a Penem Antibacterial.
Imipenem has been reported in Streptomyces canus with data available.
Imipenem is a broad-spectrum, semi-synthetic beta-lactam carbapenem derived from thienamycin, produced by Streptomyces cattleya. Imipenem binds to and inactivates penicillin-binding proteins (PBPs) located on the inner membrane of the bacterial cell wall. PBPs are enzymes that are involved in the last stages of assembling the bacterial cell wall and in reshaping the cell wall during growth and division. This inactivation results in the weakening of the bacterial cell wall and eventually causes cell lysis. Imipenem has the greatest affinity for PBP 1A, 1B, and 2, and its lethal effect is related to binding to PBP 2 and 1B. This antibiotic is active against a wide range of gram-positive and gram-negative organisms and is stable in the presence of beta-lactamases. (NCI05)
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 beta-lactamases. Clinical studies have demonstrated high efficacy in the treatment of infections of various body systems. Its effectiveness is enhanced when it is administered in combination with cilastatin, a renal dipeptidase inhibitor.
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 beta-lactamases. Clinical studies have demonstrated high efficacy in the treatment of infections of various body systems. Its effectiveness is enhanced when it is administered in combination with CILASTATIN, a renal dipeptidase inhibitor.

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Drug Indication
Imipenem is indicated, in combination with [cilastatin] with or without [relebactam], for the treatment of bacterial infections including respiratory, skin, bone, gynecologic, urinary tract, and intra-abdominal as well as septicemia and endocarditis.
FDA Label

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Mechanism of Action
Imipenem acts as an antimicrobial through the inhibition of cell wall synthesis of various gram-positive and gram-negative bacteria. 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. 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.

C12H17N3O5S

299.3461

299.093

C, 45.71; H, 5.43; N, 13.33; O, 25.37; S, 10.17

64221-86-9

Imipenem monohydrate;74431-23-5

104838

Off-white to yellow solid powder

1.6±0.1 g/cm3

530.2±60.0 °C at 760 mmHg

106-111ºC

274.5±32.9 °C

0.0±3.2 mmHg at 25°C

1.721

-2.78

3

6

6

20

491

3

S(C([H])([H])C([H])([H])/N=C(\[H])/N([H])[H])C1=C(C(=O)O[H])N2C([C@]([H])([C@@]([H])(C([H])([H])[H])O[H])[C@@]2([H])C1([H])[H])=O

VBTPAOZKIGVELK-ZXFLCMHBSA-N

InChI=1S/C12H17N3O5S/c1-6(16)9-7-4-8(21-3-2-14-5-13)11(20-12(18)19)15(7)10(9)17/h5-7,9,16H,2-4H2,1H3,(H2,13,14)(H,18,19)/t6-,7-,9-/m1/s1

(5R,6S)-6-((R)-1-Hydroxyethyl)-3-(2-(iminomethylamino)ethylthio)-7-oxo-1-azabicyclo(3.2.0)hept-2-ene-2-carbonsaeure hydrate

Primaxin; MK-0787; MK 0787; MK0787; imipenem; 64221-86-9; Imipemide; N-Formimidoylthienamycin; Imipenem anhydrous; Tienamycin; Imipenemum; N-formimidoyl thienamycin; N-Formimidoylthienamycin; Tienamycin; Imipemide; Imipenem hydrate;Recarbrio

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)