Introduction
Bacteria possess a cell wall comprising a glycopeptide polymer commonly known as peptidoglycan, which is synthesized and remodelled through the action of a family of enzymes known as "penicillin-binding proteins" (PBPs). β-lactam antibiotics, including cephalosporins, are PBP inhibitors that, through inhibition of essential PBPs, result in impaired cell wall homeostasis, loss of cell integrity, and ultimately bacterial cell death. Ceftazidime is a third-generation cephalosporin with broad-spectrum antibacterial activity, including against some treatment-resistant bacteria such as Pseudomonas aeruginosa.
Uses
Ceftazidime is an injected broad-spectrum third-generation cephalosporin beta-lactam antibiotic used to treat or prevent a variety of bacterial infections, including pneumonia, gynecological infections, bone and joint infections, and septicemia, among others.
Ceftazidime is indicated for the treatment of lower respiratory tract infections, skin and skin structure infections, urinary tract infections, bacterial septicemia, bone and joint infections, gynecologic infections, intra-abdominal infections (including peritonitis), and central nervous system infections (including meningitis) caused by susceptible bacteria.
Ceftazidime is indicated in combination with avibactam to treat infections caused by susceptible Gram-negative organisms, including complicated intra-abdominal infections (cIAI), in conjunction with metronidazole, and complicated urinary tract infections (cUTI), including pyelonephritis, in patients aged three months and older. This combination is also indicated to treat hospital-acquired and ventilator-associated bacterial pneumonia (HABP/VABP) in patients aged 18 years and older.
In all cases, to mitigate the risk of bacterial resistance and preserve clinical efficacy, ceftazidime should only be used for infections that are confirmed or strongly suspected to be caused by susceptible bacterial strains.
Associated Conditions
Pharmacodynamics
Ceftazidime is a semisynthetic, broad-spectrum, third-generation cephalosporin antibiotic that is bactericidal through inhibition of enzymes responsible for cell-wall synthesis, primarily penicillin-binding protein 3 (PBP3). Among cephalosporins, ceftazidime is notable for its resistance to numerous β-lactamases and its broad spectrum of activity against Gram-negative bacteria, including Pseudomonas aeruginosa. However, it is less active than first- and second-generation cephalosporins against Staphylococcus aureus and other Gram-positive bacteria and also has low activity against anaerobes. Ceftazidime has confirmed activity against clinically relevant Gram-negative bacteria including Citrobacter spp., Enterobacter spp., Klebsiella spp., Proteus spp., Serratia spp., _Escherichia coli, Haemophilus influenzae, Neisseria meningitidis, Pseudomonas aeruginosa, and some Gram-positive bacteria including Staphylococcus spp. and Streptococcus spp. There are also in vitro data for ceftazidime efficacy against a wide variety of other bacteria, such as Acinetobacter baumannii and Neisseria gonorrhoeae, but no clear clinical studies to support the use of ceftazidime for infections caused by these bacteria.
Although β-lactam antibiotics like ceftazidime are generally well tolerated, there remains a risk of serious acute hypersensitivity reactions, which is higher in patients with a known allergy to ceftazidime or any other β-lactam antibiotic. As with all antibiotics, ceftazidime may result in the overgrowth of non-susceptible organisms and potentially serious effects including Clostridium difficile-associated diarrhea (CDAD); CDAD should be considered in patients who develop diarrhea and, in confirmed cases, supportive care initiated immediately. Ceftazidime is primarily renally excreted such that high and prolonged serum concentrations can occur in patients with renal insufficiency, leading to seizures, nonconvulsive status epilepticus (NCSE), encephalopathy, coma, asterixis, neuromuscular excitability, and myoclonia. Treatment may lead to the development or induction of resistance with a risk of treatment failure. Periodic susceptibility testing should be considered, and monotherapy failure may necessitate the addition of another antibiotic such as an aminoglycoside. Cephalosporin use may decrease prothrombin activity, which may be improved by exogenous vitamin K. Inadvertent intra-arterial administration of ceftazidime may result in distal necrosis.
Mechanism of Action
The bacterial cell wall, which is located at the periphery of Gram-positive bacteria and within the periplasm of Gram-negative bacteria, comprises a glycopeptide polymer synthesized through cross-linking of glycans to peptide stems on alternating saccharides, which is known commonly as peptidoglycan. Cell wall formation, recycling, and remodelling require numerous enzymes, including a family of enzymes with similar active site character despite distinct and sometimes overlapping roles as carboxypeptidases, endopeptidases, transpeptidases, and transglycosylases, known as "penicillin-binding proteins" (PBPs). The number of PBPs differs between bacteria, in which some are considered essential and others redundant. In general, inhibition of one or more essential PBPs results in impaired cell wall homeostasis, loss of cell integrity, and is ultimately bactericidal.
Ceftazidime is a semisynthetic third-generation cephalosporin with broad activity against numerous Gram-negative and some Gram-positive bacteria. Like other β-lactam antibiotics, ceftazidime exhibits its bactericidal effect primarily through direct inhibition of specific PBPs in susceptible bacteria. In vitro experiments in Gram-negative bacteria such as Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae suggest that ceftazidime primarily binds to PBP3, with weaker binding to PBP1a/1b and PBP2 as well; although binding to other PBPs, such as PBP4, is detectable, the concentrations required are much greater than those achieved clinically. Similarly, ceftazidime showed binding to Staphylococcus aureus PBP 1, 2, and 3 with a much lower affinity for PBP4. Recent data for Mycobacterium abcessus suggest that ceftazidime can inhibit PonA1, PonA2, and PbpA at intermediate concentrations.
Absorption
Ceftazidime administered intravenously in healthy males produced mean Cmax values of between 42 and 170 μg/mL for doses between 500 mg and 2 g, and are reached immediately following the end of the infusion period. The Cmax for 1 g of ceftazidime administered intramuscularly is attained approximately one hour following injection and is between 37 and 43 mg/L. Following intramuscular administration of 500 mg and 1 g of ceftazidime, the serum concentration remained above 4 μg/mL for six and eight hours, respectively.
Ceftazidime Cmax and AUC show linear proportionality to the dose over the therapeutic range. In individuals with normal renal function, ceftazidime given intravenously every eight hours for 10 days as either 1 or 2 g doses showed no accumulation.
Volume of Distribution
Ceftazidime has a volume of distribution of 15-20 L.
Protein Binding
Ceftazidime plasma protein binding ranges from 5-22.8% (typically less than 10%) and is independent of concentration. Ceftazidime has been shown to bind human serum albumin.
Route of Elimination
Approximately 80% to 90% of an intramuscular or intravenous dose of ceftazidime is excreted unchanged by the kidneys over a 24-hour period. When administered intravenously, 50% of the dose appears in the urine within two hours, with another 32% of the dose appearing by eight hours post-administration.
Half Life
Ceftazidime has an elimination half-life of 1.5-2.8 hours in healthy subjects. As ceftazidime is primarily renally excreted, its half-life is significantly prolonged in patients with renal impairment. In patients with creatinine clearance < 12 mL/min, the half-life is prolonged to between 14 and 30 hours.
Clearance
The mean renal clearance of ceftazidime in healthy subjects ranges from 72 to 141 mL/min while the calculated plasma clearance is approximately 115 mL/min.
Toxicity
Ceftazidime overdosage has occurred in patients with renal failure. Reactions included seizure activity, encephalopathy, asterixis, neuromuscular excitability, and coma. Patients who receive an acute overdosage should be carefully observed and given supportive treatment. In the presence of renal insufficiency, hemodialysis or peritoneal dialysis may aid in the removal of ceftazidime from the body.
Food Interactions
No interactions found.