Pharmacokinetics of ceftibuten-cis and its trans metabolite in healthy volunteers and in patients with chronic renal insufficiency

A phase I, randomized, double-blind, placebo-controlled, ascending single- and multiple-dose study of the pharmacokinetics, safety, and tolerability of oral ceftibuten in healthy adult subjects

This was a phase I, randomized, double-blind, placebo-controlled, ascending single- and multiple-dose study of oral ceftibuten to describe the pharmacokinetics (PK) of cis-ceftibuten (administered form) and trans-ceftibuten (metabolite), and to describe safety and tolerability at higher than licensed doses. Subjects received single 400, 600, or 800 mg doses of ceftibuten on Days 1 and 4, followed by 7 days of twice-daily dosing from Days 4 to 10. Non-compartmental methods were used to describe parent drug and metabolite PK in plasma and urine. Dose proportionality was examined using C max, AUC0-12, and AUC0-INF. Accumulation was calculated as the ratio of AUC0-12 on Days 4 and 10. Adverse events (AEs) were monitored throughout the study. Following single ascending doses, mean cis- and trans-ceftibuten C max were 17.6, 24.1, and 28.1 mg/L, and 1.1, 1.5, and 2.2 mg/L, respectively; cis-ceftibuten urinary recovery accounted for 64.3%-86.9% of the administered dose over 48 h. Following multiple ascending doses, mean cis- and trans-ceftibuten C max were 21.7, 28.1, and 38.8 mg/L, and 1.4, 1.9, and 2.8 mg/L, respectively; cis-ceftibuten urinary recovery accounted for 72.2%-96.4% of the administered dose at steady state. The exposure of cis- and trans-ceftibuten increased proportionally with increasing doses. Cis- and trans-ceftibuten accumulation factor was 1.14-1.19 and 1.28-1.32. The most common gastrointestinal treatment emergent AEs were mild and resolved without intervention. Ceftibuten was well tolerated. Dose proportionality and accumulation of cis- and trans-ceftibuten were observed. These results support the ongoing development of ceftibuten at doses up to 800 mg twice-daily. (The study was registered at ClinicalTrials.gov under the identifier NCT03939429.).

Predictive Performance of Physiologically Based Pharmacokinetic and Population Pharmacokinetic Modeling of Renally Cleared Drugs in Children

Predictive performance of physiologically based pharmacokinetic (PBPK) and population pharmacokinetic (PopPK) models of drugs predominantly eliminated through kidney in the pediatric population was evaluated. After optimization using adult clinical data, the verified PBPK models can predict 33 of 34 drug clearance within twofold of the observed values in children 1 month and older. More specifically, 10 of 11 of predicted clearance values were within 1.5‐fold of those observed in children between 1 month and 2 years old. The PopPK approach also predicted 19 of 21 drug clearance within twofold of the observed values in children. In summary, our analysis demonstrated both PBPK and PopPK adult models, after verification with additional adult pharmacokinetic (PK) studies and incorporation of known ontogeny of renal filtration, could be applied for dosing regimen recommendation in children 1 month and older for renally eliminated drugs in a first‐in‐pediatric study.

Identification and Quantitative Assessment of Uremic Solutes as Inhibitors of Renal Organic Anion Transporters, OAT1 and OAT3

One of the characteristics of chronic kidney disease (CKD) is the accumulation of uremic solutes in the plasma. Less is known about the effects of uremic solutes on transporters that may play critical roles in pharmacokinetics. We evaluated the effect of 72 uremic solutes on organic anion transporter 1 and 3 (OAT1 and OAT3) using a fluorescent probe substrate, 6-carboxyfluorescein. A total of 12 and 13 solutes were identified as inhibitors of OAT1 and OAT3, respectively. Several of them inhibited OAT1 or OAT3 at clinically relevant concentrations and reduced the transport of other OAT1/3 substrates in vitro. Review of clinical studies showed that the active secretion of most drugs that are known substrates of OAT1/3 deteriorated faster than the renal filtration in CKD. Collectively, these data suggest that through inhibition of OAT1 and OAT3, uremic solutes contribute to the decline in renal drug clearance in patients with CKD.

Hepatic drug metabolism and transport in patients with kidney disease

The disposition of many drugs is altered in patients with acute (AKD) and chronic kidney disease (CKD). A decline in renal clearance of several drugs has been correlated significantly with residual renal function (ie, creatinine clearance) of subjects. Reductions in nonrenal clearance of some compounds also have been reported and associated with clearance of markers of oxidative and/or conjugative metabolism or P-glycoprotein-mediated transport. Although initial accounts of reduced hepatic microsomal cytochrome P-450 (CYP) content and activity in animal models of AKD and CKD were published almost 25 years ago, it is only in the last decade that technical advances in molecular biology and clinical pharmacology have enabled researchers to begin to characterize the phenotypic expression of individual enzymes and, importantly, distinguish the molecular and/or genetic basis for these changes. The selective modulation of hepatic CYP enzyme activity observed in kidney disease is caused, at least in part, by differentially altered expression of several CYP isoforms. This review summarizes data available through June 2003 regarding the effect of AKD and CKD on drug metabolism. Knowledge of the impact and nature of these alterations associated with kidney disease may facilitate the individualization of medication management in this patient population.

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.

Drug administration in patients with renal insufficiency. Minimising renal and extrarenal toxicity

Renal insufficiency has been associated with an increased risk of adverse effects with many classes of medications. The risk of some, but not all, adverse effects has been linked to the patient's degree of residual renal function. This may be the result of inappropriate individualisation of those agents that are primarily eliminated by the kidney, or an alteration in the pharmacodynamic response as a result of renal insufficiency. The pathophysiological mechanism responsible for alterations in drug disposition, especially metabolism and renal excretion, is the accumulation of uraemic toxins that may modulate cytochrome P450 enzyme activity and decrease glomerular filtration as well as tubular secretion. The general principles to enhance the safety of drug therapy in patients with renal insufficiency include knowledge of the potential toxicities and interactions of the therapeutic agent, consideration of possible alternatives therapies and individualisation of drug therapy based on patient level of renal function. Although optimisation of the desired therapeutic outcomes are of paramount importance, additional pharmacotherapeutic issues for patients with reduced renal function are the prevention or minimisation of future acute or chronic nephrotoxic insults, as well as the severity and occurrence of adverse effects on other organ systems. Risk factors for the development of nephrotoxicity for selected high-risk therapies (e.g. aminoglycosides, nonsteroidal anti-inflammatory drugs, ACE inhibitors and radiographic contrast media) are quite similar and include pre-existing renal insufficiency, concomitant administration of other nephrotoxins, volume depletion and concomitant hepatic disease or congestive heart failure. Investigations of prophylactic approaches to enhance the safety of these agents in patients with renal insufficiency have yielded inconsistent outcomes. Hydration with saline prior to drug exposure has given the most consistent benefit, while sodium loading and use of pharmacological interventions [e.g. furosemide (frusemide) dopomine/dobutamine, calcium antagonists and mannitol] have resulted in limited success. The mechanisms responsible for altered dynamic responses of some agents (benzodiazepines, theophylline, digoxin and loop diuretics) in renally compromised patients include enhanced receptor sensitivity secondary to the accumulation of endogenous uraemic toxins and competition for secretion to the renal tubular site of action. Application of the pharmacotherapeutic principles discussed into clinical practice will hopefully enhance the safety of these agents and optimise patient outcomes.

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.

Clinical pharmacokinetics of newer cephalosporins

Several new cephalosporins have been developed in recent years. These agents include several oral and parenteral agents with extended activity against Gram-negative pathogens. The pharmacokinetic literature for these agents is quite extensive; therefore, we have summarised this information and presented it in tabular form for critical comparison. With a few exceptions, the newer cephalosporins share similar pharmacokinetic properties. Cefixime, cefetamet pivoxil and ceftibuten differ from the others in that they exhibit nonlinear pharmacokinetic properties. The nonlinear nature of these agents is reflected by decreasing maximal concentrations with escalating doses of cefixime and cefetamet pivoxil, decreasing area under the serum concentration-time curve with increasing doses for cefixime, and a reduced bioavailability with large doses of ceftibuten. Attention to such characteristics aid the clinician in selecting appropriate dosage regimens that will optimise drug absorption. The majority of agents are primarily renally eliminated; however, renal elimination accounts for only 20% of cefixime elimination. The pharmacokinetic parameters noted for the newer cephalosporins are not influenced by multiple-dose administration, suggesting lack of drug accumulation over time. The pharmacodynamics of antimicrobials should be considered when extrapolating pharmacokinetic information into the clinical arena. In the case of the beta-lactams, the time which drug concentrations remain above some critical threshold, such as the minimal inhibitory concentration, appears to have the greatest influence on bactericidal activity. Therefore, it is important to select dosage regimens that will optimise the time serum concentrations remain above this threshold. We present an evaluation of these agents with respect to their activity against a variety of pathogens in an effort to demonstrate a pharmacokinetically-based process of antimicrobial selection.

Multiple-dose pharmacokinetics of ceftibuten after oral administration to healthy volunteers

The pharmacokinetics of ceftibuten in plasma and urine were investigated after oral administration. Twelve healthy subjects were treated orally twice daily with 400 mg of the drug for 7 days; on day 8, the subjects received a last dose of 400 mg of ceftibuten. Ceftibuten and its metabolite, the trans isomer of ceftibuten, were assayed in plasma and urine by a specific HPLC method with UV detection. Ceftibuten was rapidly absorbed, as evidenced by the mean time to the maximum observed cis-ceftibuten concentration of 2.4 h. To describe the drug intake process, a Weibull model was used. For the metabolite, the mean time to maximum concentration in plasma was 3.25 h. Mean values for the terminal half-life in plasma were 2.17 h for cis-ceftibuten and 3.19 h for trans-ceftibuten. The overall elimination half-life, tmax, and total and renal clearances of cis-ceftibuten were invariant with respect to duration of dosing. The area under the plasma concentration versus time curve from 0 to infinity and the Cmax of this drug were significantly higher on day 8 than the values predicted from the elimination half-life computed on day 1 of treatment and the dosing interval. The pharmacokinetic parameters of trans-ceftibuten were invariant with respect to duration of dosing. Ceftibuten was well tolerated; there were no clinically significant adverse clinical events. The results from the present study indicate that the levels of cis-ceftibuten in plasma as well as in urine remain above the MICs for susceptible organisms over the dosing interval.

Liquid chromatographic determination of ceftibuten, a new oral cephalosporin, in human plasma and urine

Two liquid chromatographic methods with UV detection were developed for the determination of ceftibuten in human plasma and urine. Diluted plasma samples were directly injected onto a reversed-phase column without prior protein precipitation while diluted urine samples were processed through an automated on-line sample clean-up procedure using column-switching. Both methods were linear over clinically relevant concentration ranges in plasma (from 0.1 to 50 micrograms ml-1) and urine (from 0.5 to 60 micrograms ml-1). The methods showed acceptable precision (RSD < 20%) and accuracy (bias < 15%) at the limit of quantitation (LOQ) for ceftibuten in plasma and urine. These LOQs represented the lowest concentrations of ceftibuten in plasma (0.1 micrograms ml-1) and urine (0.5 micrograms ml-1) that could be measured with acceptable precision and accuracy. RSDs for both within-day and between-day analyses were < or = 12% for plasma and < 7% for urine. These methods have been used successfully for the analysis of ceftibuten in plasma and urine following single oral doses of 200, 400 and 800 mg in man.

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)

Effects of protein binding on the isomerization of ceftibuten

Isomerization of ceftibuten to trans-ceftibuten, a less active isomer of ceftibuten, was observed in human serum in vitro. Investigation of the isomerization mechanism in the serum clarified that albumin accelerated the isomerization. The isomerization rate constant correlated significantly with the percent of binding to albumin, suggesting the binding of ceftibuten to albumin might be the driving force for the isomerization under in vitro conditions. This isomerization was also observed in clinical studies in humans. Results of physiological model analysis indicate that the isomerization catalyzed by albumin contributes significantly to the overall isomerization in the human body following oral administration.