Beta-lactam antibiotics are used to treat a variety of bacterial infections and are among the most prescribed drugs in the US.[1] Beta-lactamase inhibitors are drugs that are co-administered with beta-lactam antibiotics to prevent antibiotic resistance by inhibiting serine beta-lactamases, which are enzymes that inactivate the beta-lactam ring, which is a common chemical structure to all beta-lactam antibiotics. Therefore, beta-lactamase inhibitors are primarily indicated for infections by gram-negative bacteria, as they contain this enzyme.[2]

The most common bacteria treated by beta-lactamase inhibitors are the Enterobacteriaceae (Citrobacter, Escherichia coli, Klebsiella pneumoniae, Morganella, Proteus vulgaris, Salmonella, Shigella), Haemophilus influenzae, Mycobacterium tuberculosis, Neisseria gonorrhoeae, and Pseudomonas aeruginosa.[3] Additionally, the gram-positive bacteria Staphylococcus aureus also contains the beta-lactamase enzyme. However, beta-lactamase inhibitors are less commonly used for the treatment of staph due to the presence of an alternate antibiotic resistance mechanism, namely the presence of a penicillin-binding protein, which is ubiquitous among gram-positive bacteria.[3] Several bacteria have developed extended-spectrum beta-lactamase enzymes (ESBLs), conferring additional resistance against cephalosporin antibiotics. Enterobacteriaceae and Pseudomonas aeruginosa are notable ESBL-producing bacteria. Research has demonstrated that beta-lactamase inhibitors can effectively treat ESBL-producing organisms, thereby improving our ability to fight these virulent bacteria.[1]

Avibactam is used in combination with ceftazidime (a cephalosporin) to treat urinary tract infections, intra-abdominal infections, pyelonephritis, and hospital-acquired pneumonia caused by gram-negative bacteria, including ESBL-producing bacteria.[4] Clavulanic acid (clavulanate) is administered with the penicillin antibiotic amoxicillin and with penicillin-resistant ticarcillin.[5][6] Amoxicillin/clavulanic acid treats respiratory tract infections, otitis media, sinusitis, skin infections, and urinary tract infections, while ticarcillin/clavulanate is used to treat lower respiratory, bone, gynecologic, joint, skin, urinary tract, and abdominal infections.[5][6] Relebactam is used in combination with imipenem and cilastatin. It is used to treat pyelonephritis, urinary tract infections, and intra-abdominal infections.[7] Sulbactam is used in combination with ampicillin and is used to treat skin, intrabdominal, and gynecologic infections.[8] Tazobactam is used in combination with piperacillin to treat community-acquired pneumonia, intra-abdominal infections, skin and skin structure infections, and female pelvic infections.[9] Vaborbactam is used in combination with meropenem to treat urinary tract infections and pyelonephritis.[10] Tebipenem is a carbapenem antibiotic used to treat Mycobacterium tuberculosis that inhibits its beta-lactamase enzyme and is the only orally available beta-lactamase inhibitor.[11] However, it does not yet have approval in the United States and is only marketed in Japan. Beta-lactamase inhibitors are essential to improving the efficacy of beta-lactam antibiotic treatment and preventing antibiotic resistance, which poses a serious public health risk. New research is continuously underway to expand the number and effectiveness of beta-lactamase inhibitors.  

Beta-lactamase inhibitors work by one of two primary mechanisms. They may create substrates that bind the beta-lactamase enzyme with high affinity but form sterically unfavorable interactions, such as the acyl-enzyme. They may also develop “suicide inhibitors,” which permanently inactivate the enzyme through secondary chemical reactions in the active site. Avibactam and relebactam work by the former mechanism, while sulbactam, tazobactam, and clavulanic acid work by the latter mechanism.[12] Beta-lactamase inhibitors are generally renally excreted and do not undergo significant hepatic or GI first-pass metabolism. Their metabolism and pharmacokinetic properties are influenced by their co-administration with beta-lactam antibiotics as well as by the length of infusion, as most are delivered intravenously.

Avibactam has a half-life of approximately 2 hours, and administration is in combination with ceftazidime in a 1:4 combination. It is cleared renally with dose adjustment for patients with renal disease. The MIC is 8 mg/L at 4 mg/L avibactam concentrations. A dosing regimen of 2/0.5g ceftazidime/avibactam is used every 8 hours with a 2 hour infusion period for patients with normal kidney function.[13]

Clavulanic acid has a half-life of approximately 47 minutes with and without amoxicillin, with 37% unchanged excretion in the urine alone and 57% with amoxicillin after the first 6 hours of administration. Current dosage formulations of amoxicillin/clavulanic acid use a 4 to 1 concentration ratio.[14]

The pharmacokinetics of relebactam have been studied both alone and in combination with imipenem/cilastatin. Clearance is significantly affected by renal function as assessed by creatinine clearance. Metabolism of relebactam is not significantly affected by body weight or health status. A MIC of less than or equal to 4 micrograms/milliliter is achievable for patient groups by modifying the dosing regimens, with an optimal dose of 250 mg.[15]

Sulbactam has a half-life of one hour and a volume of distribution of 12 liters. Seventy-five percent of the dose is excreted unchanged in the urine. The pharmacokinetics of sulbactam are not significantly impacted by the co-administration of sulbactam with beta-lactam antibiotics.[16] Sulbactam is approximately 38% bound to plasma proteins. Sulbactam has demonstrated greater efficacy with prolonged infusion strategies.[17]

The pharmacological properties of tazobactam have been studied both alone and in combination with piperacillin. The mean levels of tazobactam in plasma at 4 hrs are 1.2 micrograms per milliliter with piperacillin and 0.6 micrograms per milliliter alone. The clearance of tazobactam alone is 203.5 ml/min, while that with piperacillin is 134.2 ml/min. There appears to be no significant difference in the volume of distribution, elimination half-life, the volume of distribution, or AUC from 0 to infinity hours between tazobactam alone and tazobactam with piperacillin. The total renal clearance is 73 micrograms/milliliter, the half-life is 1 hr, and the AUC from 0 to infinity is 237 micrograms*hours/ml. The maximum level of tazobactam is 6.4 micrograms/ml alone and 11.3 micrograms/ml with piperacillin. Tazobactam is excreted renally, both alone and with piperacillin. The mean 24-hour urinary excretion of tazobactam is 63.7% alone and 56.8% with piperacillin.[18]

Vaborbactam concentration has been shown to increase in a dose-dependent manner, suggesting first-order kinetics, and does not accumulate with multiple doses. The terminal half-life of vaborbactam is 2 hours. Both the volume of distribution and the plasma clearance is independent of dose. With a 2000 mg dose, the plasma clearance is 0.17 to 0.03 liters/hour, the AUC from 0 h to infinity is 144.00 13.90 mg*h/liter, and the Vss is 21.80 2.26 mg*h/liter. Vaborbactam undergoes renal excretion, and urinary recovery was 80% or greater over 48 h across all dose groups.[19] Vaborbactam does not undergo hepatic first-pass metabolism.[20]

Tebipenem shows a dose-proportional plasma concentration, with a maximum concentration reached within 1.5 hours. Between 55 and 60% of the drug is recovered in the urine. The half-life ranges from 0.8 to 1.1 hours. Renal clearance is not affected by food.[21]

The administration of many beta-lactamase inhibitor medications is via intravenous infusion over several hours. Each drug has different dosage scheduling options, allowing care providers to tailor a patient’s medication regime according to his or her unique needs. Given the potential for nephrotoxicity, dosage adjustment is a recommendation for patients with renal disease. Ceftazidime-avibactam administration is intravenous.[4] Sulbactam-ampicillin administration may be parenteral or oral.[22] Tazobactam-piperacillin administration is parenteral.[22] Clavulanic acid-amoxicillin administration is either parenteral or oral.[22] Clavulanic acid and ticarcillin administration is via the parenteral route.[22] Relebactam-imipenem-cilastatin administration is intravenous via intravenous infusion, as is Vaborbactam-meropenem.[7] Tebipenem is administered orally.[23] Poor compliance is noted among pediatric populations, particularly for dosing regimens greater than twice per day.[22] This factor merits consideration when designing a treatment regimen for pediatric patients. It is also vital to regularly counsel patients and their caregivers regarding the importance of patient compliance.

Adverse reactions associated with beta-lactamase inhibitors include gastrointestinal side effects, such as diarrhea, nausea, and constipation; nervous system effects such as headaches, insomnia, and seizures; hematological effects such as impaired platelet function; allergic reactions including anaphylaxis; pain at the injection site; and dermatologic side effects including Stevens-Johnson syndrome, toxic epidermal necrolysis, and drug-induced eosinophilia and systemic symptoms. Gastrointestinal side effects can be less severe if the patient takes the medication with food and/or water. Beta-lactamase inhibitor use is also associated with Candida and Clostridium difficile infection.[24][25][26] It is important for clinicians to monitor patients for adverse effects routinely and discontinue therapy immediately if severe side effects occur.

The use of beta-lactamase inhibitors is contraindicated in patients with a known anaphylactic reaction to penicillin antibiotics, due to the potential for cross-reactivity with other beta-lactam antibiotics and beta-lactamase inhibitors. Patients should be allergy tested to determine the presence of allergy as well as the type of allergic reaction prior to administration of beta-lactamase inhibitor therapy.[27] Beta-lactamase inhibitor therapy is also contraindicated in patients who have had previous adverse reactions to beta-lactamase inhibitors, such as neurotoxicity, hepatotoxicity, or renal toxicity. Beta-lactamase inhibitors are not contraindicated in pregnancy, although some teratogenic effects have occurred, and dose adjustments may be necessary for pregnant patients.[28]