Ertapenem

Absorption

Ertapenem is almost completely absorbed following intramuscular administration, with a mean bioavailability of approximately 90%.
Plasma concentrations of ertapenem are similar whether given intramuscularly or intravenously; however, the peak concentrations are lower when given via the intramuscular route. The time to reach the Cmax (Tmax) is slightly longer when given via the intramuscular route. Following daily intramuscular administration of one gram of ertapenem, the Tmax was approximately 2.3 hours. In healthy young adults who received a single 30-minute intravenous infusion of one gram of ertapenem, the Cmax was 155 μG/mL at 0.5 hours postdose.

Toxicity

The oral median lethal dose (LD50) in mouse is >500 mg/kg.
Intravenous administration of ertapenem at a dose of 2 g over 30 min or 3 g over 1-2 hours in healthy adults resulted in increased incidence of nausea. In clinical trials in adults, inadvertent administration of three 1 g doses of ertapenem in a 24 hour period resulted in diarrhea and transient dizziness in one patient. As there is no known antidote for ertapenem overdose, the drug should be discontinued with the initiation of general supportive treatment until renal elimination takes place. Ertapenem can be removed by hemodialysis to some extent: the plasma clearance of the total fraction of ertapenem was increased by 30% in subjects with end-stage renal disease when hemodialysis was performed immediately following administration. However, no information is available on the use of hemodialysis to treat ertapenem overdosage.

Description

Ertapenem is another synthetic carbapenem with a rather complex side chain at C-3. It is used once daily parenterally, with special application against anaerobes. As with meropenem, the 4-β-methyl group confers stability toward dehydropeptidase-1 It is not active against pseudomonads or acinetobacteria and, therefore, should not be substituted for imipenem or meropenem. It is relatively strongly bound to serum proteins, so it has a prolonged half-life, making it more convenient to use than the other carbapenems when its spectrum warrants this. Its reported indications include complicated intra-abdominal and complicated skin/skin structure infections caused by sensitive organisms (for intra-abdominal: Escheri chia coli, Clostri di um clostri doforme, Bacteroi des fragilis, and Peptostreptococcus sp; for skin/skin structures: Staphylococcus aureus (methicillin-susceptible strains), Streptococcus pyogenes, E.coli, or Peptostreptococcus sp.). It can be administered once daily.

The Uses of Ertapenem

Ertapenem is a long-acting parenteral cabapenem. Ertapenem has bactericidal activity against a variety of gram-negative pathogens, some gram positive strains, and Haemopilus influenzae. Ertapenem has shown to inactivate L,D-transpeptidase, an enzyme responsible for in vitro cross-linking of Mycobacterium tuberculosis peptidoglycan.

The Uses of Ertapenem

Antibacterial. Invanz (Merck).

Indications

Ertapenem is indicated to treat the following moderate to severe infections caused by susceptible bacteria in adult and pediatric patients (three months of age and older):
Ertapenem is also used in adults for the prophylaxis of surgical site infection following elective colorectal surgery.

Background

Ertapenem is a 1-β methyl-carbapenem that is structurally related to beta-lactam antibiotics. It was first authorized for use in the US in November 2001 and in Europe in April 2002. Shown to be effective against a wide range of Gram-positive and Gram-negative aerobic and anaerobic bacteria, ertapenem is used to treat various bacterial infections.

Definition

ChEBI: Meropenem in which the one of the two methyl groups attached to the amide nitrogen is replaced by hydrogen while the other is replaced by a 3-carboxyphenyl group. The sodium salt is used for the treatment of moderate to severe susceptible infections includ ng intra-abdominal and acute gynaecological infections, pneumonia, and infections of the skin and of the urinary tract.

Antimicrobial activity

Activity against aerobic and anaerobic pathogens is comparable to that of imipenem: MIC values for Gramnegative bacilli (with the exception of Ps. aeruginosa) are generally lower and those for Gram-positive cocci higher.
Ertapenem is stable to most serine β-lactamases, but is hydrolyzed by serine carbapenemases and metallo- β-lactamases.

General Description

Ertapenem (Invanz, for injection) is a synthetic 1-β-methylcarbapenem that is structurally related to β-lactam antibiotics,particularly the thienamycin group. Its mechanism ofaction is the same as that of other β-lactam antibiotics. Thestructure resists β-lactamases and dehydropeptidases.
Ertapenem is indicated for the treatment of moderate tosevere infections caused by susceptible strains causing complicatedintra-abdominal infections such as Escherichia,Clostridium, Peptostreptococcus, and Bacteroides. Theantibiotic is also indicated for complicated skin and skinstructure infections including diabetic foot infections (withoutosteomyelitis). Treatable strains include Staphylococcus(MSSA), Streptococcus, Escherichia, Klebsiella, Proteus,and Bacteroides. Ertapenem is also indicated for community-acquired pneumonia caused by S. pneumoniae,Haemophilus infljuenzae, and M. catarrhalis. Complicatedurinary tract infections and acute pelvic infections round outthe indications for ertapenem.

Pharmacokinetics

Ertapenem is a carbapenem antibiotic with time-dependent bactericidal activity. Its optimal bactericidal activity is achieved when drug concentrations exceed the minimal inhibitory concentrations (MIC) for a specified portion of the dosing interval.
It works against Gram-positive and Gram-negative aerobic and anaerobic bacteria. It is stable against hydrolysis by various beta-lactamases, including penicillinases, cephalosporinases, and extended-spectrum beta-lactamases, but not metallo-beta-lactamases.

Pharmacokinetics

C_max 1 g intramuscular: c. 67 mg/L after 2 h
1 g intravenous infusion (30 min): c. 155 mg/L end infusion
Plasma half-life: c. 4 h
Volume of distribution: c. 0.12 L/kg (steady state)
Plasma protein binding: 85–95%
Absorption after intramuscular injection is essentially complete with 90% bioavailability. The modestly extended plasma half-life allows once-daily dosing.
Excretion is predominantly by the renal route, about 80% being recovered in the urine within 24 h. About 40% is eliminated unchanged, the rest as a biologically inactive ringopened metabolite. Dosage should be reduced in severe renal impairment.

Clinical Use

Complicated intra-abdominal infections
Complicated skin and skin structure infections, including diabetic foot
infections without osteomyelitis
Community acquired pneumonia
Complicated urinary tract infections including pyelonephritis
Acute pelvic infections including postpartum endomyometritis, septic
abortion and postsurgical gynecologic infections
Prophylaxis of surgical site infection following elective colorectal surgery

Side Effects

Ertapenem appears to be generally well tolerated. The most common drug-related adverse experiences are diarrhea (5.5%), infused vein complication (3.7%), nausea (3.1%), headache (2.2%), vaginitis (2.1%), phlebitis/thrombophlebitis (1.3%) and vomiting (1.1%). Seizures have occasionally been reported (0.5%) in patients with a history of disorders of the CNS.

Drug interactions

Potentially hazardous interactions with other drugs Antiepileptics: concentration of valproate reduced - avoid concomitant use

Metabolism

In healthy young adults, unchanged ertapenem accounted for most plasma radioactivity. The major metabolite of ertapenem is the ring-opened derivative formed by dehydropeptidase I-mediated hydrolysis of the beta-lactam ring. This metabolite is pharmacologically inactive. Dehydropeptidase I (DHP-I) is found predominantly in the kidneys. Hepatic metabolism is negligible.

Metabolism

After intravenous infusion of radiolabelled 1 g ertapenem, the plasma radioactivity consists predominantly (94%) of ertapenem. The major metabolite of ertapenem is the ring-opened derivative formed by dehydropeptidaseI-mediated hydrolysis of the beta-lactam ring.
Approximately 80% of a dose is recovered in urine and 10% in faeces. Of the 80% recovered in urine, approximately 38% is excreted as unchanged ertapenem and approximately 37% as the ring-opened metabolite.