Imipenem

Absorption

Imipenem is not effectively absorbed from the gastrointestinal tract and therefore must be administered parenterally. The bioavailability of the IM injection is 89%.

Toxicity

In case of overdose with the combination product, including relebactam and cilastatin, it is recommended to provide supportive care. Imipenem, cilastatin, and relebactam may be removed via hemodialysis.

Description

Imipenem is a chemically stable thienamycin derivative with an antibacterial activity that is broader in spectrum and of greater potency than most of the third generation cephalosporins. Combination with cilastatin, an inhibitor of renal brush-border dehydropeptidase-I, increases both urinary and plasma levels of imipenem.

Chemical properties

White Crystals

Originator

Merck (USA)

The Uses of Imipenem

Carbapenem antibacterial.

Background

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.

Indications

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.

What are the applications of Application

Imipenem Monohydrate is a third generation cephalosporin and β-lactam carbapenem antibiotic that exhibits broad-spectrum antibacterial activity.

Definition

ChEBI: 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.

Manufacturing Process

Preparation of N-formimidoyl thienamycin:
Thienamycin (517 mg) is dissolved in pH 7 0.1 N phosphate buffer (25 ml) and cooled in an ice bath with magnetic stirring. The solution is adjusted to pH 8.5 using 2.5 N sodium hydroxide solution dispensed from an automatic burette. While maintaining a pH of 8.5, methyl formimidate hydrochloride (711 mg) is added portionwise over 2-3 minutes. After an additional 10 min, the pH of the solution is brought to 7.0 using 2.5 N hydrochloric acid. The solution is chromatographed on a column of XAD-2 resin (150 ml) which is eluted with water. The N-formimidoyl thienamycin derivative (imipenem) elutes in 1.5-2.0 column volumes (200-300 ml) and is lyophilized to a white solid (217 mg). UV (pH 7 0.1 N phosphate buffer); λmax297 nm (8,590); ir (Nujol mull) 1767 Cm-1(β-lactam).
Another method preparation of imipenem:
6-(1)-Hydroxyethyl-1-azabicyclo(3.2.0)heptane-3,7-dione-2-carboxylate is converted to the diphenoxyphosphate enol ester and this in turn reacted with N,S-bistrimethylsilyl-N-formimidoylcysteamine (use of the bistrimethylsilylated reagent is necessary in order to avoid side reactions caused by cyclization reactions). As a result the (PhO)2OPO-groups are converted to Me3SiN = CHNH-groups. Removal of the protecting groups complete the synthesis of 1- azabicyclo[3.2.0]hept-2-ene-2-carboxylic acid, 6-(1-hydroxyethyl)-3-((2- ((iminomethyl)amino)ethyl)thio)-7-oxo-, (5R-(5-alpha,6-alpha(R*)))-.

brand name

ZIENAM

Therapeutic Function

Antibiotic

Antimicrobial activity

Imipenem shows potent activity against a wide range of Grampositive and Gram-negative aerobes and anaerobes, including many resistant to other agents.Concentrations (mg/L) inhibiting 50% of strains of other organisms are: Listeria monocytogenes, 0.03; Legionella pneumophila, 0.03; Enterococcus faecium, 4; Yersinia spp., 0.06. Mycobacterium fortuitum is inhibited by 6.25 mg/L. Imipenem is active against many Pseudomonas species, but not Sten. maltophilia. It is active against most anaerobes, with the exception of Cl. perfringens, which is only moderately susceptible. It is bactericidal at 2–4 times the MIC for most species, but some strains of Staph. aureus exhibit ‘tolerance’ . Bactericidal synergy with aminoglycosides, glycopeptides, fosfomycin and rifampicin (rifampin) has been observed against many strains of Staph. aureus and enterococci.
Antibacterial activity is unaffected by the presence of cilastatin, which is itself devoid of antimicrobial activity.
Imipenem is stable to hydrolysis by most serine β-lactamases, with the exception of the group 2f carbapenem-hydrolyzingenzymes hydrolyzingenzymes . Strains of B. fragilis, Aeromonas spp. and Sten. maltophilia can produce metallo-β-lactamases that hydrolyze the drug rapidly. These strains, in addition to occasional strains of enterobacteria, Acinetobacter baumannii and Ps. aeruginosa, show variable resistance to imipenem depending upon the level of carbapenem-hydrolyzing enzymes and the presence or absence of imipenem-specific porins. Efflux pumps also exist that may extrude imipenem from Gramnegative bacteria.

Acquired resistance

Some strains of Citrobacter, Enterobacter, Proteus vulgaris, Providencia, Ps. aeruginosa and Serratia spp. may be resistant to imipenem and other β-lactam agents, often because of the selection of stably derepressed mutants expressing high levels of group 1 β-lactamases coupled with decreased intracellular drug levels due to porin mutations or increased efflux.
Induction of class 1 β-lactamases by imipenem in strains of Aeromonas, Pseudomonas and Serratia spp. is responsible for antagonism of β-lactamase-labile β-lactam agents in vitro. Imipenem resistance in Ps. aeruginosa can occur following selection of mutants that hyperproduce the group 1 cephalosporinase and which are also deficient in an outer membrane protein (OprD or D2) which specifically transports imipenem, but not cephalosporins or monobactams.

General Description

Thienamycin was found in the culture broth of Streptomyces cattleya by Merck Sharp & Dohme in 1976, as a very unstable substance. It has a unique carbapenem structure, like that of the olivanic acids found in S. olivaceus by Beecham Research Laboratories in 1979. Thienamycin shows excellent activity against a variety of pathogenic bacteria, including Pseudomonas aeruginosa. Its chemical stability has been improved by derivatization with the formimidoyl group, and its biological stability has been improved by combining it with cilastatin, an inhibitor of kidney dihydropeptidase. The combination drug imipenem – cilastatin is now under study to evaluate its clinical efficacy and safety.

Pharmacokinetics

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

Clinical Use

Lower respiratory tract infections
Urinary tract infections (complicated and uncomplicated)
Intra-abdominal infections
Gynecological infections
Bacterial septicemia
Bone and joint infections
Skin and skin structure infections
Endocarditis
Polymicrobial infections

Side Effects

CNS effects such as confusional states and seizures have been reported, especially when recommended doses were exceeded, and in patients with renal failure or creatinine clearances of ≤20 mL/min/1.73 m2.
Other reactions include phlebitis/thrombophlebitis (3.1%), nausea (2.0%), diarrhea (1.8%) and vomiting (1.5%).
Increased hepatic enzymes may be seen in adults and children. Superinfection with Aspergillus, Candida and resistant Pseudomonas spp. have been described and pseudomembranous colitis has been reported.
Patients with a history of hypersensitivity reactions to penicillins, cephalosporins or other β-lactam antibiotics should be treated cautiously with carbapenems.

Metabolism

Imipenem is metabolized by renal dehydropeptidase.