Chemical formula: C₂₂H₂₅N₃O₇S Molecular mass: 475.515 g/mol PubChem compound: 150610
Ertapenem inhibits bacterial cell wall synthesis following attachment to penicillin binding proteins (PBPs). In Escherichia coli, affinity is strongest to PBPs 2 and 3.
Similar to other beta-lactam antimicrobial agents, the time that the plasma concentration of ertapenem exceeds the MIC of the infecting organism has been shown to best correlate with efficacy in pre-clinical PK/PD studies.
For species considered susceptible to ertapenem, resistance was uncommon in surveillance studies in Europe. In resistant isolates, resistance to other antibacterial agents of the carbapenem class was seen in some but not all isolates. Ertapenem is effectively stable to hydrolysis by most classes of beta-lactamases, including penicillinases, cephalosporinases and extended spectrum beta-lactamases, but not metallo-beta-lactamases.
Methicillin-resistant staphylococci and enterococci are resistant to ertapenem, owing to PBP target insensitivity; P. aeruginosa and other non-fermentative bacteria are generally resistant, probably owing to limited penetration and to active efflux.
Resistance is uncommon in Enterobacteriaceae and ertapenem is generally active against those with extended-spectrum beta-lactamases (ESBLs). Resistance can however be observed when ESBLs or other potent beta-lactamases (e.g. AmpC types) are present in conjunction with reduced permeability, arising by the loss of one or more outer membrane porins, or with up-regulated efflux. Resistance can also arise via the acquisition of beta-lactamases with significant carbapenem-hydrolysing activity (e.g. IMP and VIM metallo-beta-lactamases or KPC types), though these are rare.
The mechanism of action of ertapenem differs from that of other classes of antibiotics, such as quinolones, aminoglycosides, macrolides and tetracyclines. There is no target-based cross-resistance between ertapenem and these substances. However, micro-organisms may exhibit resistance to more than one class of antibacterial agents when the mechanism is, or includes, impermeability to some compounds and/or an efflux pump.
Average plasma concentrations of ertapenem following a single 30 minute intravenous infusion of a 1 g dose in healthy young adults (25 to 45 years of age) were 155 micrograms/mL (Cmax) at 0.5 hour postdose (end of infusion), 9 micrograms/mL at 12 hour postdose, and 1 microgram/mL at 24 hour postdose.
Area under the plasma concentration curve (AUC) of ertapenem in adults increases nearly dose-proportionally over the 0.5 to 2 g dose range.
There is no accumulation of ertapenem in adults following multiple intravenous doses ranging from 0.5 to 2 g daily.
Average plasma concentrations of ertapenem following a single 30 minute intravenous infusion of a 15 mg/kg (up to a maximum dose of 1 g) dose in patients 3 to 23 months of age were 103.8 micrograms/mL (Cmax) at 0.5 hour postdose (end of infusion), 13.5 micrograms/mL at 6 hour postdose, and 2.5 micrograms/mL at 12 hour postdose.
Average plasma concentrations of ertapenem following a single 30 minute intravenous infusion of a 15 mg/kg (up to a maximum dose of 1 g) dose in patients 2 to 12 years of age were 113.2 micrograms/mL (Cmax) at 0.5 hour postdose (end of infusion), 12.8 micrograms/mL at 6 hour postdose, and 3.0 micrograms/mL at 12 hour postdose.
Average plasma concentrations of ertapenem following a single 30 minute intravenous infusion of a 20 mg/kg (up to a maximum dose of 1 g) dose in patients 13 to 17 years of age were 170.4 micrograms/mL (Cmax) at 0.5 hour postdose (end of infusion), 7.0 micrograms/mL at 12 hour postdose, and 1.1 microgram/mL at 24 hour postdose.
Average plasma concentrations of ertapenem following a single 30 minute intravenous infusion of a 1 g dose in three patients 13 to 17 years of age were 155.9 micrograms/mL (Cmax) at 0.5 hour postdose (end of infusion), and 6.2 micrograms/mL at 12 hour postdose.
Ertapenem is highly bound to human plasma proteins. In healthy young adults (25 to 45 years of age), the protein binding of ertapenem decreases, as plasma concentrations increase, from approximately 95% bound at an approximate plasma concentration of <50 micrograms/mL to approximately 92% bound at an approximate plasma concentration of 155 micrograms/mL (average concentration achieved at the end of infusion following 1 g intravenously).
The volume of distribution (Vdss) of ertapenem in adults is approximately 8 litres (0.11 litre/kg) and approximately 0.2 litre/kg in paediatric patients 3 months to 12 years of age and approximately 0.16 litre/kg in paediatric patients 13 to 17 years of age.
Concentrations of ertapenem achieved in adult skin blister fluid at each sampling point on the third day of 1 g once daily intravenous doses showed a ratio of AUC in skin blister fluid: AUC in plasma of 0.61.
In vitro studies indicate that the effect of ertapenem on the plasma protein binding of highly protein bound medicinal products (warfarin, ethinyl estradiol, and norethindrone) was small. The change in binding was <12% at peak plasma ertapenem concentration following a 1 g dose. In vivo, probenecid (500 mg every 6 hours) decreased the bound fraction of ertapenem in plasma at the end of infusion in subjects administered a single 1 g intravenous dose from approximately 91% to approximately 87%. The effects of this change are anticipated to be transient. A clinically significant interaction due to ertapenem displacing another medicinal product or another medicinal product displacing ertapenem is unlikely.
In vitro studies indicate that ertapenem does not inhibit P-glycoprotein-mediated transport of digoxin or vinblastine and that ertapenem is not a substrate for P-glycoprotein-mediated transport.
In healthy young adults (23 to 49 years of age), 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 dehydropeptidase-I-mediated hydrolysis of the beta-lactam ring.
In vitro studies in human liver microsomes indicate that ertapenem does not inhibit metabolism mediated by any of the six major CYP isoforms: 1A2, 2C9, 2C19, 2D6, 2E1 and 3A4.
Following administration of a 1 g radiolabelled intravenous dose of ertapenem to healthy young adults (23 to 49 years of age), approximately 80% 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.
In healthy young adults (18 to 49 years of age) and patients 13 to 17 years of age given a 1 g intravenous dose, the mean plasma half-life is approximately 4 hours. The mean plasma half-life in children 3 months to 12 years of age is approximately 2.5 hours. Average concentrations of ertapenem in urine exceed 984 micrograms/mL during the period 0 to 2 hours postdose and exceed 52 micrograms/mL during the period 12 to 24 hours post-administration.
The plasma concentrations of ertapenem are comparable in men and women.
Plasma concentrations following a 1 g and 2 g intravenous dose of ertapenem are slightly higher (approximately 39% and 22%, respectively) in healthy elderly adults (≥65 years) relative to young adults (<65 years). In the absence of severe renal impairment, no dosage adjustment is necessary in elderly patients.
Plasma concentrations of ertapenem are comparable in paediatric patients 13 to 17 years of age and adults following a 1 g once daily intravenous dose.
Following the 20 mg/kg dose (up to a maximum dose of 1 g), the pharmacokinetic parameter values in patients 13 to 17 years of age were generally comparable to those in healthy young adults. To provide an estimate of the pharmacokinetic data if all patients in this age group were to receive a 1 g dose, the pharmacokinetic data were calculated adjusting for a 1 g dose, assuming linearity. A comparison of results show that a 1 g once daily dose of ertapenem achieves a pharmacokinetic profile in patients 13 to 17 years of age comparable to that of adults. The ratios (13 to 17 years/adults) for AUC, the end of infusion concentration and the concentration at the midpoint of the dosing interval were 0.99, 1.20, and 0.84, respectively.
Plasma concentrations at the midpoint of the dosing interval following a single 15 mg/kg intravenous dose of ertapenem in patients 3 months to 12 years of age are comparable to plasma concentrations at the midpoint of the dosing interval following a 1 g once daily intravenous dose in adults (see Plasma concentrations). The plasma clearance (mL/min/kg) of ertapenem in patients 3 months to 12 years of age is approximately 2-fold higher as compared to that in adults. At the 15 mg/kg dose, the AUC value and plasma concentrations at the midpoint of the dosing interval in patients 3 months to 12 years of age were comparable to those in young healthy adults receiving a 1 g intravenous dose of ertapenem.
The pharmacokinetics of ertapenem in patients with hepatic impairment have not been established. Due to the limited extent of hepatic metabolism of ertapenem, its pharmacokinetics are not expected to be affected by hepatic impairment. Therefore, no dosage adjustment is recommended in patients with hepatic impairment.
Following a single 1 g intravenous dose of ertapenem in adults, AUCs of total ertapenem (bound and unbound) and of unbound ertapenem are similar in patients with mild renal impairment (Clcr 60 to 90 mL/min/1.73 m²) compared with healthy subjects (ages 25 to 82 years). AUCs of total ertapenem and of unbound ertapenem are increased in patients with moderate renal impairment (Clcr 31 to 59 mL/min/1.73 m²) approximately 1.5-fold and 1.8-fold, respectively, compared with healthy subjects. AUCs of total ertapenem and of unbound ertapenem are increased in patients with severe renal impairment (Clcr 5 to 30 mL/min/1.73 m²) approximately 2.6-fold and 3.4-fold, respectively, compared with healthy subjects. AUCs of total ertapenem and of unbound ertapenem are increased in patients who require haemodialysis approximately 2.9-fold and 6.0-fold, respectively, between dialysis sessions, compared with healthy subjects. Following a single 1 g intravenous dose given immediately prior to a haemodialysis session, approximately 30% of the dose is recovered in the dialysate. There are no data in paediatric patients with renal impairment.
There are inadequate data on the safety and efficacy of ertapenem in patients with advanced renal impairment and patients who require haemodialysis to support a dose recommendation. Therefore, ertapenem should not be used in these patients.
Non-clinical data reveal no special hazard for humans based on conventional studies of safety, pharmacology, repeated-dose toxicity, genotoxicity and toxicity to reproduction and development. Decreased neutrophil counts, however, occurred in rats that received high doses of ertapenem, which was not considered a significant safety issue.
Long-term studies in animals to evaluate the carcinogenic potential of ertapenem have not been performed.
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