Pharmacokinetics of intravenous cefetamet (Ro 15-8074) and oral cefetamet pivoxil (Ro 15-8075) in young and elderly subjects

Do dietary interventions exert clinically important effects on the bioavailability of β-lactam antibiotics? A systematic review with meta-analyses

BACKGROUND

Managing drug-food interactions may help to achieve the optimal action and safety profile of β-lactam antibiotics.

METHODS

We conducted a systematic review with meta-analyses in adherence to PRISMA guidelines for 32 β-lactams. We included 166 studies assessing the impact of food, beverages, antacids or mineral supplements on the pharmacokinetic (PK) parameters or PK/pharmacodynamic (PK/PD) indices.

RESULTS

Eighteen of 25 β-lactams for which data on food impact were available had clinically important interactions. We observed the highest negative influence of food (AUC or Cmax decreased by >40%) for ampicillin, cefaclor (immediate-release formulations), cefroxadine, cefradine, cloxacillin, oxacillin, penicillin V (liquid formulations and tablets) and sultamicillin, whereas the highest positive influence (AUC or Cmax increased by >45%) for cefditoren pivoxil, cefuroxime and tebipenem pivoxil (extended-release tablets). Significantly lower bioavailability in the presence of antacids or mineral supplements occurred for 4 of 13 analysed β-lactams, with the highest negative impact for cefdinir (with iron salts) and moderate for cefpodoxime proxetil (with antacids). Data on beverage impact were limited to 11 antibiotics. With milk, the extent of absorption was decreased by >40% for cefalexin, cefradine, penicillin G and penicillin V, whereas it was moderately increased for cefuroxime. No significant interaction occurred with cranberry juice for two tested drugs (amoxicillin and cefaclor).

CONCLUSIONS

Factors such as physicochemical features of antibiotics, drug formulation, type of intervention, and patient's health state may influence interactions. Due to the poor actuality and diverse methodology of included studies and unproportionate data availability for individual drugs, we judged the quality of evidence as low.

Pharmacokinetics and Target Attainment of ß-lactam Antibiotics in Older People: A Systematic Review of Current Literature

BACKGROUND AND OBJECTIVE

(Patho)physiological changes in older people may influence the pharmacokinetics (PK), and consequently the target attainment, of ß-lactam antibiotics using standard dosing regimens. This systematic review compiles the current knowledge on the PK and target attainment of ß-lactam antibiotics in older people, with the aim to identify priorities for dose optimization in this patient population.

METHODS

A systematic literature search of the PubMed and EMBASE databases was conducted. Relevant articles published prior to 1 December 2021 were identified as eligible when they included data on the PK of ß-lactam antibiotics in adults ≥ 65 years of age. Extracted information included reported PK parameters (volume of distribution, clearance [CL], elimination rate constant, intercompartmental CL, elimination half-life, area under the concentration-time curve, maximum and trough concentration), covariates on PK parameters, target attainment rate, and dosing recommendations.

RESULTS

Ninety-one relevant articles were included in this review. Four main ß-lactam subclasses were represented: 59.3% on cephalosporins + cephamycins, 25.3% on penicillins, 15.4% on carbapenems, and 3.3% on monobactams; 65.9% of articles involved intravenous administration, 16.5% mixed administration routes, 12.1% oral administration, and 5.5% intramuscular administration. The majority of studies had a small sample size, often did not include detailed information on the study population and methods, and were fairly old. CL was, on average, decreased, while elimination half-life was prolonged in aged subjects compared with young subjects. Volume of distribution was generally similar between age groups. Most studies identified renal function as the most important contributor to altered drug CL. In only 30.8% of the articles, target attainment was studied, and in 35.7% of these articles, target attainment was found to be suboptimal. Dosing recommendations were incorporated in 87.9% of articles.

CONCLUSION

Studies frequently fail to provide an evidence-based dosing recommendation for this diverse patient population. Model-based PK studies that address both physiological and disease-related changes are urgently needed. This review identified gaps of knowledge to set priorities for further research.

Challenges and innovations of drug delivery in older age

Both drug delivery performance and various age-related physical, mental and physiological changes can affect drug effectiveness and safety in elderly patients. The many drug delivery systems developed over the years include recent novel transdermal, nasal, pulmonary and orally disintegrating tablets that provide consistent, precise, timely and more targeted drug delivery. Certain drug delivery systems may be associated with suboptimal outcomes in the elderly because of the nature of drug present, a lack of appreciation of the impact of age-related changes in drug absorption, distribution and clearance, the limited availability of pharmacokinetic, safety and clinical data. Polypharmacy, patient morbidity and poor adherence can also contribute to sub-optimal drug delivery systems outcomes in the elderly. The development of drug delivery systems for the elderly is a poorly realised opportunity, with each system having specific advantages and limitations. A key challenge is to provide the innovation that best meets the specific physiological, psychological and multiple drug requirements of individual elderly patients.

Prediction of Human Glomerular Filtration Rate from Preterm Neonates to Adults: Evaluation of Predictive Performance of Several Empirical Models

The objective of this study was to evaluate the predictive performance of several allometric empirical models (body weight dependent, age dependent, fixed exponent 0.75, a data-dependent single exponent, and maturation models) to predict glomerular filtration rate (GFR) in preterm and term neonates, infants, children, and adults without any renal disease. In this analysis, the models were developed from GFR data obtained from inulin clearance (preterm neonates to adults; n = 93) and the predictive performance of these models were evaluated in 335 subjects (preterm neonates to adults). The primary end point was the prediction of GFR from the empirical allometric models and the comparison of the predicted GFR with measured GFR. A prediction error within ±30% was considered acceptable. Overall, the predictive performance of the four models (BDE, ADE, and two maturation models) for the prediction of mean GFR was good across all age groups but the prediction of GFR in individual healthy subjects especially in neonates and infants was erratic and may be clinically unacceptable.

Pharmacokinetics of cefetamet in plasma and skin blister fluid

Cefetamet pivoxil is an oral cephalosporin with enhanced affinity for the target penicillin-binding proteins 1 and 3 and an increased stability to beta-lactamases compared with older cephalosporins, such as cefalexin or cefaclor. The pharmacokinetics of cefetamet pivoxil was determined after the seventh and final dose of 500 mg of cefetamet pivoxil in eight healthy volunteers. Concentrations in plasma and cantharidin-induced skin blister fluid were determined by a high-performance liquid chromatography method. In addition, protein binding was assessed. Cmax was 4.8 +/- 1.7 micrograms/ml in skin blister fluid and 5.1 +/- 2.1 micrograms/ml in plasma. Tmax was delayed in skin blister fluid compared with plasma (3.9 +/- 1 versus 2.8 +/- 0.8 h; P < 0.001), and t1/2 was longer in skin blister fluid than in plasma (3.1 +/- 0.5 versus 2.3 +/- 0.3; P < 0.005). The mean percent penetration into cantharide blister fluid was 129% +/- 24% when measured as total drug and 149% +/- 28% when measured as free drug (P < 0.001). These data suggest that cefetamet has an excellent penetration into inflammatory interstitial fluid.

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.

Pharmacokinetics and dose proportionality of ceftibuten in men

The pharmacokinetics and dose proportionality of ceftibuten were evaluated in healthy male volunteers receiving single oral doses of 200, 400, and 800 mg of ceftibuten. The drug was absorbed with similar times to the maximum concentration of drug in plasma for all three doses. Concentrations of ceftibuten in plasma increased with increasing dose. Analysis of variance was carried out on the dose-adjusted values for the maximum concentration of drug in plasma and the area under the plasma concentration-time curve; the results indicated that the concentrations in plasma after the 200- and 400-mg doses were dose proportional, and after the 800-mg of dose they were less than dose proportional. The elimination half-life from plasma ranged from 2.0 to 2.3 h and was independent of dose. The total excretion of unchanged ceftibuten in urine accounted for 53 to 68% of the dose, and the renal clearance was estimated to be 53 to 61 ml/min after all doses. The amount of ceftibuten-trans, the major in vitro and in vivo conversion product of ceftibuten, was low in both plasma and urine.

Multiple-dose pharmacokinetics of ceftibuten in healthy volunteers

The pharmacokinetics of ceftibuten, a new cephalosporin antibiotic, and its conversion product, ceftibutentrans, were studied in healthy male volunteers following daily oral administration of a 400-mg capsule for 7 days. Mean concentrations of ceftibuten in plasma obtained on day 5 were similar to those obtained on day 7. Analysis of variance indicated that the concentrations in plasma on days 5 and 7 were at steady state. The mean accumulation factor was 1.14 for day 5 and 1.13 for day 7. The half-life (2.4 h) was independent of the duration of drug administration, and the mean maximum concentration of drug in plasma was 18 to 19 micrograms/ml. Urinary excretion was the major elimination route for ceftibuten, by which 57 to 59% of the drug was excreted unchanged over a 24-h period. The amounts of ceftibuten-trans in plasma and urine were low.

Comparative pharmacokinetics of the new oral cephalosporins

The comparative pharmacokinetics of the new oral cephalosporins (ester and nonester types), together with that of the first generation carbacephem, loracarbef, are considered in healthy volunteers. Also in this review, pharmacokinetic and microbiological data are combined in order to predict the possible clinical efficacy of this group of agents. Despite apparent similarities in the structure of these agents, single dose studies have revealed marked differences in the pharmacokinetics of the oral cephalosporins. Multiple dose studies showed no evidence of accumulation with these agents. In the elderly, only minor changes in the pharmacokinetics of the oral agents were observed, and were insufficient to warrant dosage adjustment. Unlike that of the nonester compounds, the bioavailability of the ester cephalosporins is increased when they are administered after food. Variable effects are observed when the ester agents are coadministered with antacids or H2-antagonists; while the absorption of cefetamet pivoxil was unaffected by coadministered antacids or H2-antagonists, the absorption of cefpodoxime proxetil was reduced.

Cefetamet pivoxil clinical pharmacokinetics

Cefetamet pivoxil is an orally absorbed prodrug ester of the microbiologically active cephalosporin, cefetamet. The prodrug ester is completely hydrolysed to the active compound cefetamet on its first pass through the gut wall, the liver or both. Cefetamet is classified as a third generation cephalosporin with excellent activity against streptococci, Enterobacteriaceae, Neisseria and Haemophilus species. It has enhanced stability against beta-lactamases compared with penicillins and first and second generation cephalosporins. The antibacterial spectrum is comparable with that of cefotaxime except for its poor activity against staphylococci. Following a 20-minute zero-order intravenous infusion, cefetamet had a rapid distribution phase followed by a monoexponential decline. The average pharmacokinetic parameters from 152 healthy volunteers were: total body clearance 136 ml/min (8.16 L/h); renal clearance 119 ml/min (7.14 L/h); nonrenal clearance 17 ml/min (1.02 L/h); volume of distribution at steady-state 0.29 L/kg; terminal elimination half-life 2.2 hours; 88% of the dose recovered in the urine. Cefetamet is not extensively bound to plasma proteins. Consequently, these data indicate that cefetamet is predominantly eliminated unchanged by the kidney via glomerular filtration with possibly a minor component of tubular secretion. Cefetamet has a relatively small apparent volume of distribution consistent with that of other beta-lactam antibiotics. Results following ascending intravenous doses of cefetamet in healthy young male volunteers demonstrated that the pharmacokinetics of intravenous cefetamet are independent of the dose. The absolute bioavailability of cefetamet tablets following oral cefetamet pivoxil administration is enhanced by the presence of food. Under fed conditions, 50 to 60% of the final oral dose is absorbed into the systemic circulation. This food effect is observed when cefetamet pivoxil is administered within 1 hour of a meal. Food also produces a slight delay in the time to reach peak plasma concentrations of this drug. Changes in fluid volume intake with cefetamet pivoxil administration have no effect on the bioavailability of this drug. Similar absorption characteristics have been observed for all of the tablet dosage formulations studied during clinical development. The absolute bioavailability of the final syrup dosage formulation was between 38 and 47%. Little improvement in the bioavailability of this preparation has been observed with food. The absorption and disposition of cefetamet in human subpopulations [i.e. children, elderly (< 75 years of age), renal impairment, liver disease and patients taking concomitant drugs] have been studied extensively. Only impaired renal function appears to significantly alter the elimination of this drug.(ABSTRACT TRUNCATED AT 400 WORDS)

Cefetamet pivoxil. A review of its antibacterial activity, pharmacokinetic properties and therapeutic use

Cefetamet pivoxil is an oral third-generation cephalosporin which is hydrolysed to form the active agent, cefetamet. Cefetamet has excellent in vitro activity against the major respiratory pathogens Streptococcus pneumoniae, Haemophilus influenzae, Moraxella (Branhamella) catarrhalis and group A beta-haemolytic streptococci; it is active against beta-lactamase-producing strains of H. influenzae and M. catarrhalis, but has poor activity against penicillin-resistant S. pneumoniae. Cefetamet has marked activity against Neisseria gonorrhoeae and possesses a broad spectrum of activity against Enterobacteriaceae. Both staphylococci and Pseudomonas spp. are resistant to cefetamet. Cefetamet pivoxil has been investigated in the treatment of both upper and lower community-acquired respiratory tract infections and has demonstrated equivalent efficacy to a number of more established agents, namely cefaclor, amoxicillin and cefixime. In patients with group A beta-haemolytic streptococcal pharyngotonsillitis, a 7-day course of cefetamet pivoxil was as effective as a 10-day course of the standard agent, phenoxymethylpenicillin, in this indication. In complicated urinary tract infections, cefetamet pivoxil showed similar efficacy to cefadroxil, cefaclor and cefuroxime axetil. Cefetamet pivoxil was effective in the treatment of otitis media, pneumonia, pharyngotonsillitis and urinary tract infections in children. Preliminary data indicate that single dose cefetamet pivoxil can effectively eradicate N. gonorrhoeae from both men and women. Cefetamet pivoxil has a tolerability profile similar to that of other oral cephalosporins, with gastrointestinal effects being the most commonly reported adverse events. To date, no symptoms of carnitine deficiency have been reported with cefetamet pivoxil. Cefetamet pivoxil offers effective alternative oral therapy for outpatient treatment of community-acquired respiratory tract infections, with the advantage of improved activity against H. influenzae and increased beta-lactamase stability. However, its use in areas with a high incidence of penicillin-resistant S. pneumoniae is likely to be limited. Cefetamet pivoxil is also effective in the treatment of urinary tract infections, although further trials are required to define any comparative advantages over other oral agents.

Future directions in antimicrobial chemotherapy

New developments in the treatment of bacterial infections are discussed. The most important developments include oral broad-spectrum cephalosporin derivatives and extended-spectrum injectable cephalosporins with improved activity against Gram-positive bacteria. Meropenem is a new carbapenem agent with markedly improved activity against Gram-negative bacteria. Many fluoroquinolones are in various phases of development. The most interesting new compound is sparfloxacin. Azithromycin is a new macrolide which, because of its very long half-life, attains very high levels in most tissues. Potential uses of the newer agents are discussed.

Effects of age and gender on pharmacokinetics of cefepime

The effects of age and gender on the pharmacokinetics of cefepime were examined in 48 volunteers following administration of a single 1,000-mg intravenous dose. Male and female subjects were divided into four groups, each consisting of 12 subjects, according to their age and gender. The young subjects were between 20 and 40 years of age and elderly subjects were between 65 and 81 years of age. Serial blood and urine samples were collected from each subject and were analyzed for cefepime by validated high-pressure liquid chromatographic assays with UV detection. Key pharmacokinetic parameters were calculated by noncompartmental methods. There were no gender-related differences in elimination half-life (t1/2) and weight-normalized total body clearance (CLT), renal clearance (CLR), and steady-state volume of distribution (Vss). Statistically significant age-related effects were found for t1/2, CLT, CLR, and Vss parameters. In different study groups, Vss ranged from 0.21 to 0.24 liter/kg. The values for Vss were significant greater for elderly subjects than they were for young subjects. The cefepime t1/2 was significantly longer in elderly subjects (about 3 h) than that observed in young subjects (about 2.2 h). The mean values for CLT and CLR in the four study groups ranged from 1.11 to 1.56 and 0.99 to 1.44 ml/min/kg, respectively. In elderly subjects, the estimates for CLT and CLR were significantly lower than those observed in young subjects. Linear regression revealed good correlations between clearance values of cefepime and creatinine. The magnitude of age-related changes in the pharmacokinetics of cefepime is not significant enough to recommend dosage adjustment in elderly patients with kidney functions normal for their age.

Considerations in dosage selection for third generation cephalosporins

Pharmacokinetic parameters of third generation cephalosporins vary widely, requiring different dosage regimens and adjustment methods for each agent. Although their antibacterial spectrum favours their usage in infections caused by aerobic Gram-negative organisms, due to their limited post-antibiotic effect against these organisms, dosage regimens should ensure that free drug concentrations at the site of infection remain above the minimum inhibitory concentration for as much of the dosage interval as possible in patients with normal host defence mechanisms and for the entire dosage interval in immunocompromised patients. Altered protein binding encountered in various disease states can affect both microbiological and pharmacokinetic properties especially for drugs with high protein binding. Since the concentrations at the site of action are often different from those in serum, a higher or lower range of dosages needs to be selected depending on the target site. Decreased renal function affects the elimination of most third generation cephalosporins, whereas the presence of hepatic disease does not generally necessitate dosage adjustment. Because of the complex age-related physiological changes in paediatric and elderly patients, dosage should be adjusted on the basis of the reported pharmacokinetic data in these populations. The usual recommended dose may or may not be optimal in a given condition depending on the complex interactions between pharmacokinetic, microbiological and other host factors.

Pharmacokinetics of intravenous cefetamet and oral cefetamet pivoxil in children

The pharmacokinetics of cefetamet were determined after intravenous (i.v.) administration of cefetamet and oral administration of cefetamet pivoxil syrup to patients between the ages of 3 and 12 years. The patients were hospitalized for reconstructive urological surgery; to prevent infection, prophylactic i.v. cefetamet was administered on the day of surgery and oral cefetamet pivoxil was administered 2 days later. After i.v. administration, the mean (+/- standard deviation) half-life of cefetamet was 1.97 +/- 0.60 h (n = 18), which was different from the 2.46 +/- 0.33 h reported for nine adults (22 to 68 years old) in a previous study. The average values for the mean residence times were 2.35 +/- 0.94 and 2.83 +/- 0.34 h and the average values for the fraction of the dose eliminated unchanged in the urine were 79.9% +/- 8.99% and 80% +/- 11% in children and adults, respectively. Plots of mean systemic clearance and steady-state volume of distribution versus body weight for the children and comparative adults were linear on log-log coordinates, and the slopes of the plots were 0.661 and 0.880, respectively. These slope values suggested that mean systemic clearance values per unit of body surface area were similar in children and adults and that maintenance doses for children should be the adult maintenance dose multiplied by the child's surface area divided by 1.73 m2. The mean (+/- standard deviation) oral bioavailabilities of cefetamet pivoxil were 49.3% +/- 15.7% in 3- to 7-year-old children who received a 500-mg dose and 37.9% +/- 10.0% in 8- to 12-year-old children who received a 1,000-mg dose. These values were not different from that observed in the adult group after two 500-mg tablets. Likewise, the peak concentration of cefetamet in plasma and its time of occurrence in children were in line with the values which have been observed for adults.

Pharmacokinetics of newer drugs in patients with renal impairment (Part I)

Many drugs are eliminated via the renal route and the usual dose must be modified in patients with severe renal impairment. This review is an attempt to supply physicians with the more recent data on pharmacokinetic studies of new drugs administered in uraemic patients. The review is in 2 parts: the first indicates the results of studies on the pharmacokinetics of antibiotic agents, antifungal, antiviral and antiulcer drugs, and nonsteroidal anti-inflammatory drugs. Special mention is made of epoetin (recombinant human erythropoietin). It was not possible to give all the information collected from the recent literature: since mild renal failure has little effect on the fate of a drug, pharmacokinetic data obtained in patients with a creatinine clearance (CLCR) of more than 50 ml/min has been omitted. Both the text and tables give recommendations for treating patients with moderate renal insufficiency (CLCR of about 50 ml/min), more severe renal impairment (CLCR between 10 and 50 ml/min) and end-stage renal failure with a very low creatinine clearance (below 10 ml/min). It was not possible to give uniform recommendations (i.e. reducing the dose while maintaining the same interval, or giving the same dose and prolonging the interval). This article follows the recommendations of the authors, which may vary for drugs in similar classes.

The pharmacokinetics of ceftibuten in humans

The pharmacokinetics of ceftibuten, a new oral cephalosporin, has been studied in humans. Ceftibuten is very well absorbed in young and old patients. Absorption may be slightly decreased by food or relatively high doses (800 mg). The pharmacokinetics have been well characterized in rising single-dose and multiple-dose studies. The half-life is relatively long for this class of drugs, being approximately 2-3 hr. Apparent plasma clearance (CL/F), is approximately 40-75 ml/min, and the renal clearance is approximately 30-50 ml/min, corresponding to the fraction excreted unchanged in the urine of approximately 60%-70% of the dose. The apparent volume of distribution after oral dosing (Vd/F) was approximately 0.2 L/kg. The half-life, plasma clearance, renal clearance, and fraction excreted in urine are not affected by increasing dose and are constant during multiple dosing. There is little drug accumulation during multiple dosing. Drug elimination is decreased in patients with renal insufficiency and dosing in these patients should be adjusted relative to creatinine clearance values. The drug penetrates very well to experimentally induced inflammatory fluid but produces negligible levels in breast milk. The drug has no effect on the pharmacokinetics of theophylline. The drug is well tolerated and has pharmacokinetic properties that are clinically advantageous.

Influence of antacid and ranitidine on the pharmacokinetics of oral cefetamet pivoxil

The purpose of this investigation was to assess the influence that treatment with antacid and ranitidine had on the pharmacokinetics of oral cefetamet pivoxil in 18 healthy male volunteers. Each subject received, in an open-labeled, randomized, three-way crossover design, a single oral dose of 1,000 mg (two tablets) of cefetamet pivoxil 10 min after a standard breakfast during each of the following treatments: treatment A, control period; treatment B, antacid (80 ml of suspension; Maalox 70) administered on the evening before cefetamet pivoxil dosing (-12.5 h) and again 2 h before and 2 h after a standard breakfast; treatment C, ranitidine (150 mg) administered twice a day for 4 days and again 1 h and 10 min prior to cefetamet pivoxil dosing. Plasma and urine samples were collected over a 24-h period following cefetamet pivoxil administration. Cefetamet was analyzed by high-performance liquid chromatography. Oral bioavailability parameters (area under the concentration-time curve from 0 to 12 h, area under the concentration-time curve from 0 h to infinity, time to maximum concentration of drug in plasma, and maximum concentration of drug in plasma) were obtained by noncompartmental techniques. The results showed that none of these bioavailability parameters was significantly (P greater than 0.05) affected by antacid or rantidine coadministration. A compartmental analysis showed no significant differences. In addition, the terminal elimination half-life and the fraction of cefetamet excreted unchanged in the urine was also not significantly (P greater than 0.05) affected by antacid or ranitidine exposure. Relatively wide intrasubject variability was observed for time to maximum concentration of drug in plasma and terminal elimination half-life in several of the 18 subjects studied. Although these irregularities did not appear to be strongly associated with a particular treatment, they increased in subjects in both the antacid and H2-receptor antagonist treatment groups compared with those in subjects in the control treatment group. We conclude that antacid and ranitidine treatment likely does not alter the bioavailability of oral cefetamet pivoxil.

Effects of timing of food and fluid volume on cefetamet pivoxil absorption in healthy normal volunteers

Cefetamet pivoxil (1,000 mg orally) absorption was evaluated in 16 male subjects (age, 23.4 +/- 1.7 years; weight, 73.9 +/- 7.0 kg) 1 h before (BE), with (WI), and 1 h after (AF) a standard breakfast. The time to peak concentration of cefetamet in plasma (Tmax) was increased from 3.25 +/- 1.44 h in the BE group to 4.31 +/- 1.54 and 4.13 +/- 1.54 h in the WI and AF groups, respectively (P less than 0.05). The maximum cefetamet concentration in plasma (Cmax) and the area under the plasma cefetamet concentration-time profiles (AUC) in the BE, WI, and AF groups were 5.50 +/- 1.06, 5.47 +/- 1.4, and 6.57 +/- 0.93 micrograms/ml and 38.2 +/- 10.1, 35.7 +/- 11.9, and 42.8 +/- 6.8 micrograms.h/ml, respectively. The Cmax and AUC values were not different between the BE and WI groups (P greater than 0.05). However, differences in these values were found between the WI and AF groups (P less than 0.05). The effect of fluid volume intake on cefetamet pivoxil (1,000 mg orally) absorption was evaluated in 12 male subjects (age, 23.8 +/- 2.3 years; weight, 74.9 +/- 9.0 kg) under fasted and WI conditions. Increasing fluid volume intake from 250 to 450 ml under the fasted condition had no effect on the absorption of the prodrug (Tmax, 2.50 +/- 0.52 versus 2.83 +/- 0.94 h; Cmax, 4.89 +/- 1.04 versus 4.84 +/- 0.89 micrograms/ml; AUC, 29.6 +/- 5.1 versus 30.7 +/- 7.1 micrograms.h/ml; P greater than 0.05. Thus, independent of fluid volume intake, cefetamet pivoxil absorption is enhanced when it is given within 1 h of a meal, and it is recommended that the prodrug should be taken during this period of increased bioavailability.

Pharmacokinetics of intravenous cefetamet and oral cefetamet pivoxil in patients with hepatic cirrhosis

The pharmacokinetics of orally administered cefetamet pivoxil and intravenously administered cefetamet were studied in 12 healthy subjects and 12 patients with hepatic cirrhosis without ascites. Cirrhosis had no detectable effect on the pharmacokinetics of cefetamet and on the bioavailability of cefetamet pivoxil. After intravenous cefetamet in control versus cirrhotic subjects, respectively, the following mean +/- standard deviation values were observed: total body clearance, 128 +/- 10.2 versus 123 +/- 28.8 ml/min; steady-state volume of distribution, 23.2 +/- 2.2 versus 22.7 +/- 4.6 liters; half-life, 2.42 +/- 0.21 versus 2.35 +/- 0.41 h. Renal and nonrenal clearances of cefetamet were similar in both groups, as were the mean residence times and areas under the plasma concentration-time curve. For oral cefetamet pivoxil, no differences were detected in the mean values of the percentage of dose absorbed: 44.6 +/- 9.1 versus 50.1 +/- 12.9. The rate of appearance of cefetamet in the plasma also was not affected by cirrhosis: similar mean values were found for the mean residence time and the maximum concentration in plasma and its time of occurrence.

[Pharmacokinetics of cefixime in volunteers and a literature comparison with the new ester prodrug cephalosporins]

The pharmacokinetic parameters of cefixime were determined in healthy volunteers following oral administration of 200 mg cefixime as tablet, syrup and dry suspension, respectively. All three galenic formulations showed reliable absorption. Mean peak plasma concentrations amounted to 2.4-3.4 mg/l and were reached after 3.3-3.5 h. Mean terminal half-lives were 2.9-3.1 h. The mean areas under the plasma concentration-time curves ranged between 18 and 26 mg/l.h; 18-24% of the dose administered were recovered unchanged in the urine. The best bioavailability was obtained with the dry suspension followed by the tablet and the syrup. With respect to the ester pro-drug cephalosporins, cefuroxime axetil, cefetamet pivoxyl and cefotiam hexetil, cefixime exhibits higher plasma half-life and area under the curve as well as, comparable absolute bioavailability but consistently lower urinary recovery which indicates higher non-renal clearance.

Pharmacokinetics of intravenous cefetamet and oral cefetamet pivoxil in patients with renal insufficiency

The pharmacokinetics of cefetamet after a short intravenous infusion of cefetamet (515 mg) and oral administration of 1,000 mg of cefetamet pivoxil were studied in 9 healthy subjects and in 38 patients with various degrees of renal impairment. The results showed that cefetamet elimination was dependent on renal function. After intravenous dosing, total body (CLS), renal (CLR), and nonrenal (CLNR) clearances were linearly related to creatinine clearance (CLCR; r = 0.95, 0.92, and 0.59, respectively). Elimination half-life (t1/2 beta) was prolonged from 2.46 +/- 0.33 h in normal subjects to 29.1 +/- 13.9 h in patients with CLCR of less than 10 ml/min per 1.73 m2. Correspondingly, CLS and CLR decreased from 1.77 +/- 0.27 and 1.42 +/- 0.25 ml/min per kg to 0.14 +/- 0.04 and 0.04 +/- 0.03 ml/min per kg, respectively. The volume of distribution at steady state (0.298 +/- 0.049 liter/kg) for cefetamet was not altered by renal insufficiency (P greater than 0.05). After oral administration, the elimination parameters, t1/2 beta and CLR, were insignificantly different from the intravenous data (P greater than 0.05). Furthermore, the bioavailability (F) of cefetamet pivoxil (45 +/- 13%) was not altered by renal failure (P greater than 0.05). However, maximum concentration in plasma and the time to achieve this value were significantly increased (5.86 +/- 0.74 versus 14.8 +/- 6.14 micrograms/ml and 3.9 +/- 1.1 versus 8.4 +/- 1.7 h, respectively; P less than 0.05). Based on these observations, it is recommended that patients with CLcr of <10 ml/min per 1.73 m2 and between 10 and 39 ml/min per 1.73 m2 be given one-quarter of the normal daily dose either once or twice daily. Patients with CLcr between 40 and 80 ml/min per 1.73 m2 should receive one-half of the normal dose twice daily. For patients with CLcr of <10 ml/min per 1.73 m2, it would be recommended that they receive a normal standard dose as a loading dose on day 1 of treatment.

Pharmacokinetics of cefetamet pivoxil (Ro 15-8075) with ascending oral doses in normal healthy volunteers

The pharmacokinetics of cefetamet pivoxil during administration of ascending oral doses were studied in 16 male normal healthy volunteers (age, 24.5 +/- 2.1 years; weight, 73.5 +/- 8.5 kg). The subjects were randomly assigned to four oral treatments of 500, 1,000, 1,500, and 2,000 mg of cefetamet pivoxil according to a four-by-four Latin square design. After an overnight fast, the drug was administered 10 min after a standard breakfast. It was found that both the rate and extent of prodrug absorption, measured as cefetamet adsorption, were reduced with increasing doses. The time to maximum concentration of cefetamet in serum was delayed from 4.00 +/- 0.81 to 4.88 +/- 0.96 h (P less than 0.05) when the dose of cefetamet pivoxil was increased from 500 to 2,000 mg. The dose-normalized values of area under the curve from 0 h to infinity for cefetamet and fraction of dose excreted as cefetamet were reduced by averages of 10.3 and 12.5%, respectively, over the dose range studied (P less than 0.05). The changes in rate and extent of prodrug absorption are thought to be the main factors contributing to the nonlinear relationship between maximum concentration in serum and dose. The change in absorption characteristics of cefetamet pivoxil with dose is, however, expected to have few clinical consequences because the magnitudes of these changes are comparable with their respective intragroup variations.

Pharmacokinetics of oral cefetamet pivoxil (Ro 15-8075) and intravenous cefetamet (Ro 15-8074) in humans: a review

Cefetamet pivoxil belongs to the class of orally absorbed pro-drug esters which are hydrolyzed to the active compound (cefetamet) on their first pass through the gut wall and/or the liver. The intravenously administered cefetamet is eliminated predominantly unchanged in the urine by glomerular filtration. Systemic and renal clearance values for cefetamet were 140 and 130 ml/min, respectively. The plasma protein binding is 22%, whereby the only binding protein is albumin. The steady state volume of distribution (0.29 l/kg) corresponds roughly to the extracellular water space which is consistent with other low protein-bound cephalosporins. In general, after intravenous doses, cefetamet follows the kinetic behaviour of a cephalosporin with low protein binding, limited non-renal clearance, and renal clearance that is predominantly due to glomerular filtration, e.g. ceftizoxime, ceftazidime. After oral administration, cefetamet pivoxil shows a significant food effect (F = 41% vs 51%). Hence, cefetamet pivoxil is recommended to be taken after food. The food effect, however, is not of such a magnitude that it will be of clinical consequence when this recommendation is not followed. The food effect is not related to a change in gastric pH because antacids and ranitidine do not affect the absorption of cefetamet pivoxil, although in approximately 20% of the subjects absorption of the drug is delayed. The elimination of cefetamet is directly proportional to renal function. In patients with varying degrees of renal insufficiencies, dosage should be decreased accordingly. Age has no effect on the bioavailability of cefetamet pivoxil. However, the clearance of cefetamet is higher in children and lower in the elderly.