Pharmacokinetics and pharmacodynamics of oral cephalexin in children with osteoarticular infections

Cefadroxil and cephalexin pharmacokinetics and pharmacodynamics in children with musculoskeletal infections

Cephalexin, a first-generation cephalosporin, is the first-line oral therapy for children with musculoskeletal infections due to methicillin-susceptible Staphylococcus aureus (MSSA). Cefadroxil, a similar first-generation cephalosporin, is an attractive alternative to cephalexin given its longer half-life. In this study, we describe the comparative pharmacokinetics (PK) and pharmacodynamics (PD) of cephalexin and cefadroxil in children with musculoskeletal infections. Children aged 6 months to 18 years with a musculoskeletal infection were enrolled in a prospective, open-label, crossover PK study and given single oral doses of cefadroxil (50-75 mg/kg up to 2,000 mg) and cephalexin (50 mg/kg up to 1,375 mg). Population PK models were developed and used for dosing simulations. Our primary PD target was the achievement of free antibiotic concentrations above the minimum inhibitory concentration (fT >MIC) for 40% of the day for MICs ≤ 4 mg/L. PK of cephalexin (n = 15) and cefadroxil (n = 14) were best described using a one-compartment, first-order absorption model, with a lag time component for cefadroxil. PK parameters were notable for cefadroxil's longer half-life (1.61 h) than cephalexin's (1.10 h). For pediatric weight bands, our primary PD target was achieved by cephalexin 25 mg/kg/dose, maximum 750 mg/dose, administered three times daily and cefadroxil 40 mg/kg/dose, maximum 1,500 mg/dose, administered twice daily. More aggressive dosing was required to achieve higher PD targets. Among children with musculoskeletal infections, oral cephalexin and cefadroxil achieved PD targets for efficacy against MSSA. Given less frequent dosing, twice-daily cefadroxil should be further considered as an alternative to cephalexin for oral step-down therapy for serious infections due to MSSA.

Clinical Practice Guideline by the Pediatric Infectious Diseases Society (PIDS) and the Infectious Diseases Society of America (IDSA): 2023 Guideline on Diagnosis and Management of Acute Bacterial Arthritis in Pediatrics

This clinical practice guideline for the diagnosis and treatment of acute bacterial arthritis (ABA) in children was developed by a multidisciplinary panel representing the Pediatric Infectious Diseases Society (PIDS) and the Infectious Diseases Society of America (IDSA). This guideline is intended for use by healthcare professionals who care for children with ABA, including specialists in pediatric infectious diseases and orthopedics. The panel's recommendations for the diagnosis and treatment of ABA are based upon evidence derived from topic-specific systematic literature reviews. Summarized below are the recommendations for the diagnosis and treatment of ABA in children. The panel followed a systematic process used in the development of other IDSA and PIDS clinical practice guidelines, which included a standardized methodology for rating the certainty of the evidence and strength of recommendation using the GRADE approach (Grading of Recommendations Assessment, Development and Evaluation) (see Figure 1). A detailed description of background, methods, evidence summary and rationale that support each recommendation, and knowledge gaps can be found online in the full text.

A Systematic Review on the Clinical Pharmacokinetics of Cephalexin in Healthy and Diseased Populations

Cephalexin is a first-generation β-lactam antibiotic used in adults and pediatrics to treat various streptococcal and staphylococcal infections. This review aims to summarize and evaluate all the pharmacokinetic (PK) data on cephalexin by screening out all pertinent studies in human beings following the per oral (PO) route. By employing different online search engines such as Google Scholar, PubMed, Cochrane Central, and Science Direct, 23 studies were retrieved, among which nine were in healthy subjects, five in diseased ones, and the remaining were drug-drug, drug-food, and bioequivalence-related. These studies were included only based on the presence of plasma concentration-time profiles or PK parameters, i.e., maximum plasma concentration (Cmax), half-life (t1/2) area under the curve from time 0-infinity (AUC0-∞), and clearance (CL/F). A dose-proportional increase in AUC0-∞ and Cmax can be portrayed in different studies conducted in the healthy population. In comparison to cefaclor, Cmax was recorded to be 0.5 folds higher for cephalexin in the case of renal impairment. An increase in AUC0-∞ was seen in cephalexin on administration with probenecid, i.e., 117 µg.h/mL vs. 68.1 µg.h/mL. Moreover, drug-drug interactions with omeprazole, ranitidine, zinc sulfate, and drug-food interactions for cephalexin and other cephalosporins have also been depicted in different studies with significant changes in all PK parameters. This current review has reported all accessible studies containing PK variables in healthy and diseased populations (renal, dental, and osteoarticular infections, continuous ambulatory peritoneal dialysis) that may be favorable for health practitioners in optimizing doses among the latter.

Effectiveness of oral cephalexin in antibiotic-course completion for methicillin-susceptible Staphylococcus aureus-induced bacteremic vertebral osteomyelitis

BACKGROUND

Methicillin-susceptible Staphylococcus aureus (MSSA) is the most common causative microorganism of pyogenic vertebral osteomyelitis (PVO). Although oral antimicrobial therapy with first-generation cephalosporins can treat MSSA infection, data on PVO are scarce. This study evaluated the treatment efficacy of cephalexin as oral antibiotic therapy for MSSA-induced PVO.

METHODS

This retrospective study included adult patients treated with oral cephalexin as the completing treatment for PVO with MSSA bacteremia from 2012 to 2020. Treatment effectiveness of cephalexin was evaluated by comparing improvement (5-point scale; score ≥ 4/5 indicates treatment success) in symptoms and laboratory and imaging results between intravenous antimicrobial and oral cephalexin treatment.

RESULTS

Among 15 participants (8 [53%] women; median [interquartile range, IQR], age 75 [67.5-80.5] years; Charlson Comorbidity Index 2 [0-4]), 10 (67%) had lumbar spine lesions, 12 (80%) had spinal abscesses, and 4 (27%) had remote abscesses; no patients had concomitant endocarditis. In 11 patients with normal renal function, cephalexin 1,500-2,000 mg/day was administered. Five patients (33%) underwent surgery. Median (IQR; range) duration (days) of intravenous antibiotics, cephalexin, and total treatment was 36 (32-61; 21-86), 29 (19-82; 8-251), and 86 (59-125; 37-337), respectively. Cephalexin had an 87% treatment success rate without recurrence during a median follow-up of 119 (IQR, 48.5-350) days.

CONCLUSIONS

In patients with MSSA bacteremia and PVO, antibiotic treatment completion with cephalexin is a reasonable option, even in cases with spinal abscess, if at least 3 weeks of effective intravenous antimicrobial therapy is provided.

Developmental Pharmacokinetics of Antibiotics Used in Neonatal ICU: Focus on Preterm Infants

Neonatal Infections are among the most common reasons for admission to the intensive care unit. Neonatal sepsis (NS) significantly contributes to mortality rates. Empiric antibiotic therapy of NS recommended by current international guidelines includes benzylpenicillin, ampicillin/amoxicillin, and aminoglycosides (gentamicin). The rise of antibacterial resistance precipitates the growth of the use of antibiotics of the Watch (second, third, and fourth generations of cephalosporines, carbapenems, macrolides, glycopeptides, rifamycins, fluoroquinolones) and Reserve groups (fifth generation of cephalosporines, oxazolidinones, lipoglycopeptides, fosfomycin), which are associated with a less clinical experience and higher risks of toxic reactions. A proper dosing regimen is essential for effective and safe antibiotic therapy, but its choice in neonates is complicated with high variability in the maturation of organ systems affecting drug absorption, distribution, metabolism, and excretion. Changes in antibiotic pharmacokinetic parameters result in altered efficacy and safety. Population pharmacokinetics can help to prognosis outcomes of antibiotic therapy, but it should be considered that the neonatal population is heterogeneous, and this heterogeneity is mainly determined by gestational and postnatal age. Preterm neonates are common in clinical practice, and due to the different physiology compared to the full terms, constitute a specific neonatal subpopulation. The objective of this review is to summarize the evidence about the developmental changes (specific for preterm and full-term infants, separately) of pharmacokinetic parameters of antibiotics used in neonatal intensive care units.

Shedding Light on Amoxicillin, Amoxicillin-clavulanate, and Cephalexin Dosing in Children from a Pharmacist's Perspective

Selection of an antibiotic and dosing regimen requires consideration of multiple factors including microbiological data, site of infection, pharmacokinetics, and how it relates to the pharmacodynamic target. Given the multiple dosage regimens of amoxicillin with/without clavulanate and cephalexin, we review the principles of dose selection from a pharmacist's perspective.

Cefadroxil Comparable to Cephalexin: Minimum Inhibitory Concentrations among Methicillin-Susceptible Staphylococcus aureus Isolates from Pediatric Musculoskeletal Infections

Cephalexin and cefadroxil are oral first-generation cephalosporins used to treat methicillin-susceptible Staphylococcus aureus (MSSA) infections. Despite its shorter half-life, cephalexin is more frequently prescribed, although cefadroxil is an appealing alternative, given its slower clearance and possibility for less frequent dosing. We report comparative MIC distributions for cefadroxil and cephalexin, as well as for oxacillin, cephalothin, ceftaroline, and cefazolin, for 48 unique clinical MSSA isolates from pediatric patients with musculoskeletal infections. Both cefadroxil and cephalexin had MIC50 values of 2 μg/mL and MIC90 values of 4 μg/mL. MIC50s for oxacillin, cephalothin, and ceftaroline were ≤0.25 μg/mL, and cefazolin's MIC50 was 0.5 μg/mL. While cefadroxil and cephalexin MICs are higher than those for other active agents, the distributions of MICs for cefadroxil and cephalexin are statistically equivalent, suggesting similar in vitro MSSA activities. Cefadroxil should be further considered an alternative agent to cephalexin, although additional work is needed to identify the optimal dose and frequency of these antibiotics for the treatment of serious MSSA infections. IMPORTANCE Cephalexin and cefadroxil are oral antibiotics that are used to treat serious infections due to the bacteria MSSA. While cephalexin is used more commonly, cefadroxil is excreted from the body more slowly; this generally allows patients to take cefadroxil less frequently than cephalexin. In this study, we compared the abilities of cefadroxil, cephalexin, and several other representative intravenous antibiotics to inhibit the growth of MSSA in the laboratory. Bacterial samples were obtained from children with bone, joint, and/or muscle infections caused by MSSA. We found that cefadroxil and cephalexin inhibited the growth of MSSA at similar concentrations, suggesting similar antibacterial potencies. The selected intravenous antistaphylococcal antibiotics generally inhibited bacterial growth with lower antibiotic concentrations. Based on these results, cefadroxil should be further considered an alternative oral antibiotic to cephalexin, although future research is needed to identify the optimal dose and frequency of these antibiotics for serious infections.

Outpatient management of moderate cellulitis in children using high-dose oral cephalexin

Objectives

To evaluate the effectiveness of a high-dose (HD) oral cephalexin treatment guideline for children with moderate cellulitis treated as outpatients.

Methods

In this retrospective cohort study, we included children who presented to the emergency department (ED) with moderate cellulitis and treated according to the institution’s HD oral cephalexin guideline over a 2-year period. All children had standardized follow-up at a medical day hospital (MDH). Treatment was considered effective in the absence of treatment failure, defined as admission, switch to IV treatment or ED visit within 2 weeks of discharge from the MDH. Safety was ascertained by recording adverse events and severe complications at follow-up.

Results

A total of 123 children were treated as outlined in the guideline, including 117 treated with HD oral cephalexin. The success rate was 89.7% (105/117). Among 12 (10.3%) children who had treatment failure, 10 (8.5%) required admission, 1 (0.9%) received IV antibiotics at the MDH and 1 (0.9%) had a return visit to the ED without admission. No severe complications were reported; four abscesses required drainage and one patient had a rash. The mean number of visits per child at the MDH was 1.6 (SD 1.0).

Conclusions

With a success rate of 89.7%, HD oral cephalexin seems effective and safe for the treatment of children with moderate cellulitis. Its use potentially reduces hospitalization rates for this condition and decreases the need for IV insertion.

Model-Informed Precision Dosing of Antibiotics in Osteoarticular Infections

As a heterogeneous and wide inflammation, osteoarticular infection (OAI) shows an increasing incidence in recent years. Staphylococcus aureus is the most important pathogen causing OAI. The antibiotic treatment will affect the outcomes of OAI patients, and the drug selection and dosage regimen highly rely on patients’ variability, pathogen susceptibility, and drug property like bone permeability. Model-informed precision dosing (MIPD) provides options to describe and quantify the pharmacokinetic (PK) variability of the OAI population using different models, such as the population pharmacokinetic (PPK) model and physiological-based pharmacokinetic (PB/PK) model. In the present review, we highlighted that the MIPD of antibiotics played a critical role in OAI and listed the dose regimen recommended by the model. Collectively, our current study provided a valuable reference for the treatment of patients and improved the safety and efficiency of drug use.

Frequency of Dosing of Cephalexin for Oral Step-Down Therapy of Pediatric Osteoarticular Infections Caused by Methicillin-Sensitive Staphylococcus Aureus

Osteoarticular infections are one of the more common invasive bacterial infections encountered in children. There exist significant practice variations in both the diagnosis and treatment of such infections. However, the practice of transitioning from parenteral therapy to oral antibiotics has been well validated by several studies. For methicillin-sensitive Staphylococcus aureus (MSSA), cephalexin is often recommended. Prospective, controlled data regarding optimal dosing of cephalexin in pediatric osteomyelitis are not available. We sought to review our retrospective, uncontrolled data on four times daily (QID) versus three times daily (TID) dosing of cephalexin for pediatric osteoarticular infections. Children ≥1 month to <18 years of age admitted to Rady Children's Hospital-San Diego with a diagnosis of osteomyelitis or septic arthritis between January 1, 2002, and November 30, 2007, were identified and previously reported. Only patients with culture-positive MSSA infections are included in this report. Demographic and clinical data were manually extracted from the electronic medical record. Fifty-nine patients were treated with cephalexin and had records available for review through our electronic medical record. Thirty-eight patients (64.4%) were treated QID, and 21 patients (35.6%) were treated TID. Clinical cure was achieved in all patients with only one adverse event occurring in the QID group. In this retrospective chart review of children with osteoarticular infections caused by MSSA treated with cephalexin, similar clinical outcomes were found with QID versus TID dosing.

Twice- and Thrice-daily Cephalexin Dosing for Staphylococcus aureus Infections in Children

BACKGROUND

Cephalexin is used for the treatment of methicillin-susceptible Staphylococcus aureus (MSSA) infections in children. Although 4 times daily dosing is recommended, less frequent dosing regimens are often prescribed to improve treatment acceptability and adherence. We developed a population pharmacokinetic model of cephalexin in children to determine a twice-daily (BID) and thrice-daily (TID) cephalexin dosing regimen for MSSA infections.

METHODS

A population pharmacokinetic model was developed using a nonlinear mixed effects modeling approach. The dataset used was from a prospective open-label pharmacokinetic study of orally administered cephalexin in 12 children 1-16 years of age with bone and joint infections. Simulations were performed to determine a BID and TID dosing regimen so that ≥90% of children in this age group would achieve the pharmacodynamic target for MSSA (ie, time that the free drug concentration exceeds the minimum inhibitory concentration of the bacteria for at least 40% of the dosing interval).

RESULTS

The final model was 1 compartment with a transit compartment model to account for delay in oral absorption. For BID dosing, doses of 22-45 and 80 mg/kg were required for MSSA with minimum inhibitory concentrations of 1-2 and 4 mg/L, respectively. For TID dosing, the respective required doses were 15-25 and 45 mg/kg.

CONCLUSIONS

Our study proposes a BID and TID cephalexin dosing regimen that can be prospectively evaluated. Through reducing the dose frequency of this widely prescribed antibiotic, we can reduce the medication burden for children and improve treatment compliance for MSSA infections.

Pharmacokinetic and pharmacodynamic considerations of cephalosporin use in children

Introduction: Cephalosporins are a major class of antibiotics, frequently used in children because of their remarkable antibacterial activity and excellent safety profile. Time above the minimal inhibitory concentration of the non-protein-bound fraction (fT>MIC) is the pharmacokinetic/pharmacodynamic parameter that correlates with the therapeutic efficacy. In the pediatric population, the inter-individual variability in cephalosporin pharmacokinetics is large because of maturational changes. However, the prescription of cephalosporins promotes emergence of Enterobacteriaceae producing broad-spectrum ß-lactamases.Areas covered: Here we describe in vitro activities and the main pharmacokinetic characteristics of cephalosporins in children. On the basis of these characteristics, we propose an estimation of the fT>MIC for each molecule as a tool to help optimize the use of cephalosporins. We also provide an inventory of the clinical use of cephalosporins and present prospects for the development of new molecules or associations to address the emergence of resistant strains.Expert opinion: Cephalosporins represent a heterogeneous group of antibiotics with various pharmacokinetics and in vitro antimicrobial activity that the clinician needs to master to optimize their use. However, their broad use plays a role in the emergence of broad-spectrum ß-lactamase-producing strains and must thus be restricted to probabilistic broad-spectrum therapy and situations without therapeutic alternatives.

Management of Pediatric Acute Hematogenous Osteomyelitis, Part I: Antimicrobial Stewardship Approach and Review of Therapies for Methicillin-Susceptible Staphylococcus aureus, Streptococcus pyogenes, and Kingella kingae

Acute hematogenous osteomyelitis (AHO), often occurring in young children, is the most frequently diagnosed type of osteomyelitis in pediatric patients. Optimizing antibiotics is essential as delays to receipt of appropriate therapy can lead to chronic osteomyelitis, as well as impairments in bone growth and development. Antimicrobial stewardship programs (ASPs) are in a key position to help improve the care of patients with AHO as they contain a pharmacist with expertise in antibiotic drug selection, optimization of dosing, and microbiologic test review. A literature search of the MEDLINE database was conducted from initiation through January 2018. Articles selected for the review focus on pathogen identification, pharmacokinetics and pharmacodynamics, efficacy and safety in children, transition from intravenous to oral therapy, duration of treatment, and antimicrobial stewardship interventions. This review will highlight the potential roles ASPs can have in improving the management of AHO in pediatric patients. These roles include the creation of clinical pathways, improving testing algorithms, antibiotic choice and dosing, intravenous to oral transitions, duration of treatment, and therapy monitoring. Overall, patients are most effectively treated by focusing treatments on age, presentation, local sensitivities, and directed therapy with pathogen identification.

Diagnosis and management of acute osteoarticular infections in children

Acute hematogenous osteomyelitis and septic arthritis are not uncommon infections in children and should be considered as part of the differential diagnosis of limb pain and pseudoparalysis. Most bone infections in children arise secondary to hematogenous seeding of bacteria into bone. The most common pathogens are Staphylococcus aureus and Kingella kingae. Children with septic arthritis should be evaluated promptly by orthopedic specialists for aspiration and possible debridement of concomitant osteomyelitis. Optimal empiric therapy after appropriate cultures continues to be intravenous cefazolin. In most cases, conversion to oral antimicrobials should occur when the patient has clinically improved and has decreasing inflammatory markers. For most uncomplicated cases of osteomyelitis, current recommendations are 3 to 4 weeks of antimicrobial therapy compared with the 6 weeks previously recommended.

Integration of pharmacokinetic and pharmacodynamic indices of valnemulin in broiler chickens after a single intravenous and intramuscular administration

The antibacterial efficacy of valnemulin against Staphylococcus aureus was studied ex vivo in broiler chickens after intravenous and intramuscular administration at a dose of 10 mg/kg bodyweight (BW). The minimum inhibitory concentrations (MICs) of valnemulin against S. aureus strains ATCC 25923 in broth and serum were 0.12 and 1 µg/mL, respectively. The MIC50 and MIC90 of valnemulin against all susceptible S. aureus strains isolated from chickens in the test population were 0.06 and 0.12 μg/mL, respectively. Protein binding, which greatly influences the efficacy of valnemulin, was assayed by equilibrium dialysate in vitro. A high binding fraction of 86.2% was found, which seems in good agreement with the difference of bacterial susceptibility tests observed in broth and serum. The surrogate index of AUC0-24/MIC required for the lowest bacteriostatic effect, and 2 log10CFU reduction in bacterial count were 24.4 h and 38.0 h, respectively. The required daily dose of valnemulin for a bacteriostatic activity was calculated to be 15 mg/kg BW based on the MIC90 of 0.12 µg/mL. Considering the slow disposition process of valnemulin and an AUC0-24 h value of more than 10-fold obtained from diseased animals, a suggested dose of 3 mg/kg BW is sufficient to achieve a satisfactory therapeutic efficacy in infected broilers. Due to the time-dependent antibacterial characteristics of valnemulin, the recommended daily dose should be split into two or three sub-doses to achieve the highest effectiveness while diminishing the risk of development of bacterial resistance.