Single-dose pharmacokinetics of ceftibuten (SCH 39720) in infants and children

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.

Application and synthesis of thiazole ring in clinically approved drugs

The development of heterocyclic derivatives has progressed considerably over the past few decades, and many new agents of synthetic and natural origin have been produced. Among heterocyclic compounds, thiazole is a unique five-membered heterocyclic motif characterized by nitrogen and sulfur atoms, which is widely used as an important core skeleton in a variety of pharmaceutically important compounds due to their diverse biological activities, such as antibacterial, antivirus, and antifungal. To the best of our knowledge, more than 90 thiazole-containing derivatives have been currently under clinical investigation, and some thiazole analogs have been approved to treat various diseases. As the potentially privileged scaffolds, thiazole derivatives can be further extensively explored to search for new drugs characterized by improved therapeutic efficacy and similar biological targets. This review aims to outline the applications and synthetic routes of some representative thiazole-containing drugs approved in the clinic, which may guide medicinal researchers to rationally design more effective thiazole-containing drug candidates.

Development of Physiologically Based Pharmacokinetic Model for Pregabalin to Predict the Pharmacokinetics in Pediatric Patients with Renal Impairment and Adjust Dosage Regimens: PBPK Model of Pregabalin in Pediatric Patients with Renal Impairment

Pregabalin (PGB) is widely used clinically; however, its pharmacokinetics (PK) has not been studied in pediatric patients with renal impairment (RI). To design optimized PGB regimens for pediatric patients with varying degrees of RI and predict exposure to PGB, physiologically based pharmacokinetic (PBPK) models of PGB were developed and verified, and its disposition was simulated in the healthy population and adults with RI. The simulated results from the PBPK models after single-dose and multi-dose administrations of PGB were consistent with the corresponding observed data based on the fold error values of less than 2. The area under curve ratios were 1.23 ± 0.06, 2.02 ± 0.10, 3.86 ± 0.21, and 9.92 ± 0.79 in pediatric patients with mild, moderate, severe, and end-stage RI, respectively. Based on the predictions for pediatric patients with moderate, severe, and end-stage RI, the maximum dose should not exceed 7, 3.5, and 1.4 mg/kg/day, respectively, among those weighing < 30 kg, and it should not exceed 5, 2.5, and 1 mg/kg/day, respectively, among those weighing > 30 kg. In conclusion, the developed PBPK model is a valuable tool for predicting PGB dosage for pediatric patients with RI.

Probability of achieving requisite pharmacodynamic exposure for oral beta-lactam regimens against Haemophilus influenzae in children

OBJECTIVE

To define contemporary levels of resistance of Haemophilus influenzae to antibacterials commonly used to treat children for bacterial respiratory infections, and to assess the probability of achieving the requisite pharmacodynamic exposures for regimens against recent respiratory H. influenzae isolates using Monte Carlo simulation.

METHODS

233 H. influenzae isolates obtained from pediatric outpatients with acute otitis media (n = 55), sinusitis (n = 58), or lower respiratory tract infections ( n = 120) from 1 November 2004 to 30 April 2005 were characterized for beta-lactamase production and susceptibility to a panel of 10 beta-lactam antimicrobials. 5000 concentration-time profiles were simulated for US FDA-approved doses of oral amoxicillin, amoxicillin/clavulanic acid, cefpodoxime, cefprozil, ceftibuten, and cefuroxime using pharmacokinetics and weights of 5-year old male children. The probability of attaining free drug concentrations above the minimum inhibitory concentration (MIC) for 50% of the dosing interval (50% fT > MIC) was assessed for each regimen against this population of H. influenzae.

RESULTS

beta-Lactamase production was demonstrated in 67 (28.8%) of the H. influenzae isolates and varied by isolation site (38% acute otitis media, 36% sinusitis, and 21% lower respiratory tract infections). Regarding susceptibility, the rank order of the tested antimicrobials was ceftriaxone = cefixime (100%) > cefpodoxime (99.6%) > ceftibuten = amoxicillin/clavulanic acid (99.1%) > cefdinir (98.7%) > cefuroxime (97.4%) > cefprozil (93.1%) > cefaclor (92.3%) > amoxicillin (63.1%). The most active agents based on pharmacodynamic assessment (50% fT > MIC) were cefpodoxime (98.9%), ceftibuten (95.3%), and high-dose amoxicillin/clavulanic acid (90.4%). Several amoxicillin regimens also achieved a high likelihood of pharmacodynamic target attainment (91.8- 98.6%) when beta-lactamase-positive strains were excluded from the analysis.

CONCLUSION

Against H. influenzae, the antibacterials most likely to achieve optimal in vivo exposures in children are cefpodoxime, ceftibuten, and amoxicillin/clavulanic acid.

Pharmacodynamic target attainment of oral beta-lactams for the empiric treatment of acute otitis media in children

OBJECTIVE

To determine the probability of oral beta-lactam regimens achieving bactericidal pharmacodynamic exposure against pathogens causing acute otitis media (AOM) given contemporary prevalence and resistance rates.

METHODS

A 5000-patient Monte Carlo simulation was used to recreate steady-state concentration-time profiles for oral drug administration regimens of amoxicillin, amoxicillin/clavulanic acid, cefpodoxime, cefprozil, ceftibuten, and cefuroxime in a population of 12.5-month-old children. The percent of simulated children in whom free drug concentrations above the minimum inhibitory concentration (MIC) for 50% of the drug administration interval (50% fT>MIC) were achieved was determined; 180 middle ear fluid isolates (56 Haemophilus influenzae and 124 Streptococcus pneumoniae) collected during the 2004 Global Respiratory Antimicrobial Surveillance Project (GRASP) were used. The cumulative fraction of response (CFR) was calculated and weighted against the prevalence of organisms causing AOM extrapolated from the literature. The contribution of a 'Pollyanna phenomenon' for each organism was also incorporated to estimate clinical effectiveness.

RESULTS

Against S. pneumoniae isolates, amoxicillin 30 mg/kg every 8 hours (84.7%) achieved the greatest CFR followed by amoxicillin/clavulanic acid and the other amoxicillin-based regimens. Against H. influenzae isolates, cefpodoxime, ceftibuten, and amoxicillin/clavulanic acid each achieved a CFR of >90%. When weighted by the prevalence of AOM-causing pathogens, CFR was highest for cefpodoxime (87.5%), amoxicillin/clavulanic acid (85.7%), and amoxicillin 30 mg/kg every 8 hours (70.8%). The contribution of a 'Pollyanna phenomenon' increased the probability of clinical effectiveness for all agents, with amoxicillin/clavulanic acid (90.2%) and cefpodoxime (90.1%) having the highest weighted CFR.

CONCLUSIONS

Based on the recent epidemiologic and resistance profiles of S. pneumoniae and H. influenzae, amoxicillin/clavulanic acid (45 mg/kg every 12 hours) and cefpodoxime (5 mg/kg every 12 hours) provide the greatest likelihood of achieving optimal pharmacodynamic exposures empirically in children with AOM.

Analysis of recent antimicrobial agents in human biological fluids by high-performance liquid chromatography

Our previous review on the liquid chromatographic (LC) analysis of anti-bacterial agents was published in 1990 in a special issue of the Journal of Chromatography. Eight years later, some new agents have been registered and numerous other are under clinical experiment. In spite of therapeutic problems encountered with certain bacterial pathogens, the development of novel drug candidates has slowed partially due to the need for identification of new bacterial targets and the cost of the research. The present overview updates the LC methods for the quantitations of recent antimicrobial agents (marketed and in clinical development) in human biological fluids. Consideration has been given to procedures permitting the determination of isomers and metabolites as well as methods regarding tissue extracts or liquid sampled from physiological sanctuaries. LC methods are available for the quantitation of almost all registered or investigated recent anti-infective drugs and some are applicable in routine practice. Nevertheless, few techniques have been validated for the determination in tissue extracts limiting the development of penetration studies.

Comparison of the efficacy and safety of a short course of ceftibuten with that of amoxycillin/clavulanate in the treatment of acute exacerbations of chronic bronchitis

The efficay and safety of short course ceftibuten (400 mg od for 5 days; n = 163) were compared with that of amoxycillin/clavulanate (AMX/CA) (250/125 mg tds for 10 days; n = 172) in a multicentre, single-blind, parallel-group trial in 335 adults with acute exacerbations of chronic bronchitis (AECB). Clinical response was equivalent, with cure or improvement in 134/145 (92.4%) ceftibuten-treated patients and 139/150 (92.7%) AMX/CA-treated patients (95% CI: -7.00%, +6.50%). The overall eradication rates were similar (ceftibuten 88.3%; AMX/CA 87.5%) and also the incidence of adverse events which occurred in 24/163 (14.7%) ceftibuten-treated and 27/172 (15.5%) AMX/CA-treated patients. Ceftibuten 400 mg od for 5 days is as effective and well tolerated as AMX/CA 250 mg tds for 10 days in the treatment of AECB.

Human variability and noncancer risk assessment- An analysis of the default uncertainty factor

A 10-fold uncertainty factor is used for noncancer risk assessments to allow for possible interindividual differences between humans in the fate of the chemical in the body (kinetics) and target organ sensitivity (dynamics). Analysis of a database on the variability in each of these aspects is consistent with an even subdivision of the 10-fold factor into 10(0.5) (3.16) for kinetics and 10(0.5) (3.16) for dynamics. Analysis of the number of subjects in a normally and log-normally distributed population which would not be covered by factors of 3.16 supports this subdivision and also the use of a 10-fold factor to allow for both aspects. Analysis of kinetic data for subgroups of the population indicates that the standard default value of 3.16 for kinetics will not be adequate for all routes of elimination and all groups of the population. A scheme is proposed which would allow the selection of appropriate default uncertainty factors based on knowledge of the biological fate and effects of the chemical under review. Copyright 1998 Academic Press.

Ceftibuten: a new expanded-spectrum oral cephalosporin

OBJECTIVE

To review the antimicrobial activity, pharmacokinetics, clinical efficacy, and tolerability of ceftibuten, a new expanded-spectrum oral cephalosporin.

DATA SOURCES

Literature was identified by a MEDLINE search (January 1983-June 1996) of the medical literature, review of English-language literature and bibliographies of these articles, and data on file.

STUDY SELECTION

Clinical efficacy data were selected from all published and unpublished trials and abstracts that mentioned ceftibuten. Additional information concerning in vitro susceptibility, safety, chemistry, and pharmacokinetic profile of ceftibuten also was reviewed.

DATA SYNTHESIS

Ceftibuten, an oral expanded-spectrum cephalosporin, has a broad spectrum of activity against many gram-negative and selected gram-positive organisms, including Streptococcus pneumoniae, Streptococcus pyogenes, Moraxella catarrhalis, and Haemophilus influenzae. Ceftibuten is stable to hydrolysis by many common beta-lactamases. Ceftibuten is rapidly and almost completely absorbed from the gastrointestinal tract and is primarily eliminated renally as unchanged drug. The elimination half-life of ceftibuten is slightly longer than 2 hours. Efficacy has been demonstrated in a number of clinical trials in adults and children with upper and lower respiratory tract infections (e.g., acute otitis media, pharyngitis, sinusitis, bronchitis) and urinary tract infections. The adverse effect profile is equal to that of comparator agents.

CONCLUSIONS

Ceftibuten is an alternative to other antimicrobial agents with convenient once-daily dosing in the treatment of upper and lower respiratory tract infections. Similar to other oral expanded-spectrum cephalosporins, ceftibuten has antimicrobial activity against common pathogens of the respiratory tract and is stable in the presence of many beta-lactamases. The clinical choice of an oral expanded-spectrum cephalosporin will be based on patient acceptance, frequency of administration, and cost.

Pharmacokinetics of cefixime in children with urinary tract infections after a single oral dose

The pharmacokinetics of cefixime, a third-generation broad-spectrum cephalosporin, were determined following administration of a 8 mg/kg single oral dose of cefixime suspension to six children with urinary tract infections, ages from 6 to 13 years and weights from 17 to 60 kg. Blood samples for determination of plasma cefixime concentrations were obtained for up to 12 hr and complete urine collections were obtained for urinary excretion of unchanged parent drug for up to 24 hr after administration. Plasma and urine concentrations of cefixime were determined using a reversed phase HPLC assay and pertinent pharmacokinetic parameters were estimated by model-independent standard methods. Mean peak plasma concentration was 4.04 micrograms/ml and was reached after 3.2 hr. The mean area under the plasma concentration-time curve was 33.07 micrograms.hr/ml and the mean elimination half-life was 3.91 hr. The mean apparent total clearance was 4.74 ml/min./kg and about 15% of the dose administered was recovered unchanged in urine. In conclusion, the estimated pharmacokinetic values of cefixime were comparable to those observed in healthy adult subjects based on equivalent mg/ kg doses. Plasma and urine concentrations of the drug were well above the reported minimal plasma and urinary concentrations for most common urinary tract pathogens for up to 12 and 24 hr after administration, respectively.

Comparison of cefprozil, cefpodoxime proxetil, loracarbef, cefixime, and ceftibuten

OBJECTIVE

To discuss the pharmacokinetics, spectrum of activity, clinical trials, and adverse effects of cefprozil, cefpodoxime proxetil, loracarbef, cefixime, and ceftibuten, an investigational cephalosporin.

DATA SOURCES

Literature was identified by a MEDLINE search from 1986 to January 1995.

STUDY SELECTION

Randomized, controlled studies were selected for evaluation; however, uncontrolled studies were included when data were limited for indications approved by the Food and Drug Administration.

DATA EXTRACTION

Data were evaluated with respect to in vitro activity, study design, clinical and microbiologic outcomes, and adverse drug reactions.

DATA SYNTHESIS

Cefprozil, cefpodoxime proxetil, loracarbef, cefixime, and cefributen are active in vitro against organisms frequently involved in community-acquired infections such as Streptococcus pneumoniae, Escherichia coli, beta-lactamase-positive or -negative Haemophilus influenzae, and Moraxella catarrhalis. Except for cefixime and ceflibuten, they all are active against methicillin-susceptible Staphylococcus aureus. Even though there were problems in study design (discussed within the text), clinical data demonstrate that these new oral beta-lactam compounds are as efficacious as conventional therapies for a variety of community-acquired infections.

CONCLUSIONS

Cefprozil, cefpodoxime, cefixime, loracarbef, and ceftibuten demonstrate in vitro activity against the major organisms that cause community-acquired infections. Clinical trials confirm that these agents are as effective as traditional therapies for the management of acute otitis media, pharyngitis/tonsillitis, sinusitis, bronchitis, pneumonia, urinary tract infections, and skin and skin-structure infections. In addition, cefixime and cefpodoxime are effective therapies for uncomplicated gonococcal infections. Selection of a specific agent will be influenced by susceptibility data and safety, as well as issues of compliance and cost.

High-performance liquid chromatographic determination of ceftibuten and its metabolite in biological fluids: applications in pharmacokinetic studies

An HPLC method with UV detection was developed for the analysis of ceftibuten (cis-isomer) and its metabolite (trans-isomer of ceftibuten) in plasma and urine. The detection was performed at 254 nm. The procedure for the plasma assay involves the addition of an internal standard (ceftazidime), followed by treatment of the samples with acetonitrile and dichloromethane. The urine samples, after dilution (10- to 40-fold), were analyzed by a column-switching technique without internal standard. The proposed technique is reproducible, selective, reliable, and sensitive. Linear detector responses were observed for the calibration curve standards in the ceftibuten conentration range of 0.10 to 20 mg/L for plasma and 0.10 to 50 mg/L for urine, and in the metabolite concentration range of 0.20 to 4 mg/L for plasma and 0.20 to 16 mg/L for urine. The limit of quantitation is 0.1 mg/L for ceftibuten and 0.2 mg/L for the transisomer in plasma and urine. The reproducibility of the analytical method according to the statistical coefficients is approximately 7%. The accuracy of the method is good; that is, the relative error is < 5%. The methods were applied to pharmacokinetic studies of ceftibuten after multiple oral administration (400 mg every 12 h for 8 days) to healthy volunteers.

Ceftibuten. A review of its antibacterial activity, pharmacokinetic properties and clinical efficacy

Ceftibuten is an orally active third generation cephalosporin which has a broad spectrum of in vitro antibacterial activity, encompassing the majority of Gram-negative pathogens and streptococci, and which shows greater stability than several other cephalosporins against bacteria producing extended-spectrum beta-lactamases. In clinical studies, ceftibuten (generally 400 mg/day in adults or 9 mg/kg/day in children, administered once daily) was effective in the treatment of acute uncomplicated or complicated urinary tract infections, demonstrating an efficacy similar to that of cefaclor (1500 mg/day), and similar or superior to that of cotrimoxazole (trimethoprim/sulfamethoxazole; 8/40 mg/kg/day) in children. The majority of patients with acute or chronic lower respiratory tract infections responded to treatment with ceftibuten, and response rates were similar to those achieved with cefaclor (750 or 1500 mg/day). Ceftibuten 9 mg/kg/day was at least as effective as cefaclor and as effective as amoxicillin/clavulanic acid (both 40 mg/kg/day) in children with acute otitis media, and was superior to phenoxymethylpenicillin (penicillin V; 25 mg/kg/day) in children and adolescents with streptococcal pharyngitis or scarlet fever caused by Group A beta-haemolytic streptococci. Ceftibuten was well tolerated in most patients, with adverse events (mostly mild to moderate gastrointestinal disturbances) generally occurring in 5 to 10% of patients. Thus, ceftibuten, with a once- or twice-daily oral dosage regimen, good tolerability profile and activity against a wide range of bacterial organisms, offers a promising alternative to other agents (including cefaclor, cotrimoxazole, amoxicillin/clavulanic acid, bacampicillin and phenoxymethylpenicillin) for the treatment of patients with urogenital and respiratory tract infections. Its place in therapy will be more clearly defined following further large comparative trials, in which it is likely to prove most useful in patients with infections caused by beta-lactamase-producing pathogens.

Ceftibuten pharmacokinetics and pharmacodynamics. Focus on paediatric use

Ceftibuten is an extended-spectrum, cephem antimicrobial agent formulated for oral administration. Ceftibuten is absorbed by carrier-mediated processes and passive diffusion. The absorption of ceftibuten is described adequately by a first-order process. Following oral administration, peak serum ceftibuten concentrations are reached within 2 to 3 hours. Although the absolute bioavailability of ceftibuten in humans is not known, its relative bioavailability indicates that there is relatively rapid and complete absorption of the drug. Administration of ceftibuten with food may decrease the rate of absorption and, in the case of high fat meals, may decrease the extent of absorption by approximately 20 to 30%. The results of limited studies indicate that the drug distributes well into various body tissues and fluids, with relatively high concentrations being achieved in organs that receive a significant portion of the cardiac output. In adults with normal renal function or chronic renal failure, the apparent volume of distribution (Vd/F) for ceftibuten ranges from 0.2 to 0.4 L/kg and the total plasma clearance (CL/F) ranges from approximately 61 to 75 ml/min (3.7 to 4.5 L/h). Studies of ceftibuten elimination in adults have demonstrated positive linear correlation between CL/F and creatinine clearance. Following administration of a single dose of ceftibuten, approximately 67 to 94% of the drug has been recovered in the urine unchanged. The elimination half-life (t1/2 beta) of ceftibuten in adults with normal renal function is approximately 2.5 hours. Significant accumulation of ceftibuten does not occur with repeated administration. Despite the fact that the mean time taken to achieve maximal serum concentration (tmax) [1.1 to 2 hours] and t1/2 beta (2.1 hours) following administration of a single dose of ceftibuten to infants and children were similar to values previously reported in adults, the Vd/F (0.42 L/kg) and CL/F (3.1 ml/h/kg) were considerably greater in children younger than 5 years. Additionally, the apparent nonrenal clearance of ceftibuten in paediatric patients (52% of CL/F) was greater than reported for adults (approximately 32% of CL/F) with normal renal function. Thus, developmental differences appear to affect the pharmacokinetic profile of ceftibuten. Ceftibuten has a wide spectrum of antimicrobial activity against both Gram-positive and Gram-negative pathogens, and is stable to hydrolysis by a large number of beta-lactamases. Notable exceptions with regard to the Gram-positive spectrum for ceftibuten include relative or documented resistance for most strains of Listeria, Staphylococcus aureus, S. epidermidis, penicillin-resistant strains of Streptococcus pneumonia and S. enterococcus.(ABSTRACT TRUNCATED AT 400 WORDS)

Pharmacokinetic studies in paediatric patients. Clinical and ethical considerations

Important advances in paediatric clinical pharmacology have been made over the past 2 decades. However, there remains a reluctance to pursue pharmacodynamic and pharmacokinetic studies in children and, consequently, many important therapeutic agents have not been adequately studied in this population. Age-related pharmacokinetic/pharmacodynamic studies are not only essential to provide optimal drug therapy for children, but are quite feasible. Usually, paediatric pharmacokinetic studies are conducted in children receiving treatment for a specific medical condition. The approach to soliciting participation of paediatric subjects requires special sensitivity to the fears and anxieties of the child and the parents. Factors influencing subject enrollment and suggestions to enhance enrollment into study protocols are discussed. Pharmacokinetic/pharmacodynamic studies require repeated measurements over time and often entail obtaining multiple blood and urine samples. Techniques for reducing sample volume and number of necessary samples while minimising the discomfort and fear associated with obtaining multiple samples include the development of highly sensitive analytical methods to measure drug concentrations in small volume samples. The number of samples obtained from individual subjects can be minimised by using pharmacokinetic analytical approaches such as the nonlinear mixed effect model (NONMEM) which allows estimation of pharmacokinetic characteristics of a population using limited data from each subject. In addition, less invasive methods to measure drug metabolism/elimination such as salivary sampling, transcutaneous collection and breath analysis have been applied to the study of certain drugs. Children are a particularly vulnerable population because of their limited cognitive abilities and dependence on adults. Thus, they must be afforded greater protection from exploitation as research subjects than that provided to adults.