Absolute bioavailability of cefixime in man

Cefazolin as a predictor of urinary cephalosporin activity in indicated Enterobacterales

Traditionally, cephalothin susceptibility results were used to predict the susceptibility of additional cephalosporins; however, in 2013-2014, the Clinical and Laboratory Standards Institute (CLSI) revisited this practice and determined that cefazolin is a more accurate proxy than cephalothin for uncomplicated urinary tract infections (uUTIs). Therefore, a cefazolin surrogacy breakpoint was established to predict the susceptibility of seven oral cephalosporins for Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis in the context of uUTIs. Clinical microbiology laboratories face several operational challenges when implementing the cefazolin surrogacy breakpoint, which may lead to confusion for the best path forward. Here, we review the historical context and data behind the surrogacy breakpoints, review PK/PD profiles for oral cephalosporins, discuss challenges in deploying the breakpoint, and highlight the limited clinical outcome data in this space.

Clinical trial protocol to evaluate the efficacy of cefixime in the treatment of early syphilis

BACKGROUND

Syphilis rates have been increasing both in the USA and internationally with incidence higher among men-who-have-sex-with-men and people living with human immunodeficiency virus (HIV) infection. Currently, benzathine penicillin is the recommended treatment for syphilis in all patients. Global shortages and cost increases in benzathine penicillin call for alternative treatment options. This study evaluates the efficacy of oral cefixime for the treatment of early syphilis.

METHODS

We are conducting a randomized, multisite, open-label, non-comparative clinical trial in Los Angeles and Oakland, CA. Eligible participants are ≥ 18 years old, with primary, secondary, or early latent syphilis (rapid plasma reagin [RPR] titer ≥ 1:8). Patients with HIV infection must have a viral load ≤ 200 copies/mL and CD4+ T cell count ≥ 350 cells/μL during the past 6 months. Participants are randomized to receive either 2.4 M IU benzathine penicillin G intramuscularly once or cefixime 400 mg orally twice a day for 10 days. Participants return at 3, 6, and 12 months post-treatment for follow-up RPR serological testing. The primary outcome is the proportion of participants who achieve ≥ 4-fold RPR titer decrease at 3 or 6 months post-treatment.

DISCUSSION

Clinical trials evaluating the efficacy of alternative antibiotics to penicillin are urgently needed.

TRIAL REGISTRATION

Clinicaltrials.gov NCT03660488 . Registered on 4 September 2018.

Biliary Excretion-Mediated Food Effects and Prediction

Many orally administered drugs with negative food effects (i.e., lower exposure under fed conditions) are often primarily or partially eliminated by biliary excretion. The aim of this study is to assess the potential correlation between a negative food effect and biliary excretion. Correlation analysis was conducted using a training dataset containing 27 drugs which met the following criteria: (1) immediate-release formulations, (2) shows a negative food effect, (3) > 10% biliary clearance, and (4) does not undergo extensive metabolism. A correlation between fed-state biliary clearance (CL_b,fed) and fasted-state biliary clearance (CL_b,fast) (y = 1.81*x, R² = 0.68) was observed. The 1.8-fold increase in biliary clearance was then used as a correction factor to improve physiologically based pharmacokinetic (PBPK) prediction of food effects for 12 test drugs. The mean deviations of predicted fed/fasting AUC ratio and C_max ratio from clinically observed values were reduced from 32.4 to 17.2% and from 63.3 to 54.3%, respectively. In contrast to the positive food effects on most biopharmaceutics classification system (BCS) class II drugs for which food-stimulated bile flow increases drug solubility and absorption, our results suggest that the elimination of biliary excreted drugs is increased by food-stimulated bile flow, resulting in negative food effects.

Phase II trial evaluating the clinical efficacy of cefixime for treatment of active syphilis in non-pregnant women in Brazil (CeBra)

BACKGROUND

Syphilis is a sexually and vertically transmitted infection caused by the bacteria Treponema pallidum for which there are few proven alternatives to penicillin for treatment. For pregnant women infected with syphilis, penicillin is the only WHO-recommended treatment that will treat the mother and cross the placenta to treat the unborn infant and prevent congenital syphilis. Recent shortages, national level stockouts as well as other barriers to penicillin use call for the urgent identification of alternative therapies to treat pregnant women infected with syphilis.

METHODS

This prospective, randomized, non-comparative trial will enroll non-pregnant women aged 18 years and older with active syphilis, defined as a positive rapid treponemal and a positive non-treponemal RPR test with titer ≥1:16. Women will be a, domized in a 2:1 ratio to receive the oral third generation cephalosporin cefixime at a dose of 400 mg two times per day for 10 days (n = 140) or benzathine penicillin G 2.4 million units intramuscularly based on the stage of syphilis infection (n = 70). RPR titers will be collected at enrolment, and at three, six, and nine months following treatment. Participants experiencing a 4-fold (2 titer) decline by 6 months will be considered as having an adequate or curative treatment response.

DISCUSSION

Demonstration of efficacy of cefixime in the treatment of active syphilis in this Phase 2 trial among non-pregnant women will inform a proposed randomized controlled trial to evaluate cefixime as an alternative treatment for pregnant women with active syphilis to evaluate prevention of congenital syphilis.

TRIAL REGISTRATION

Trial identifier: www.Clinicaltrials.gov, NCT03752112. Registration Date: November 22, 2018.

A Phase 1 Pharmacokinetic and Safety Study of Extended-Duration, High-dose Cefixime for Cephalosporin-resistant Neisseria gonorrhoeae in the Pharynx

BACKGROUND

There are no fully oral recommended treatment regimens for gonorrhea. Inadequately treated pharyngeal gonococcal infections are a likely reservoir for transmission and development of antimicrobial resistance. We sought to determine an oral cefixime dosing regimen that would theoretically treat pharyngeal infections by gonococci with minimum inhibitory concentrations 0.5 μg/mL.

METHODS

We conducted an open-label, nonrandomized, phase I pharmacokinetic and safety study of cefixime in 25 healthy male and female volunteers divided into 4 dosing cohorts (cohort A, 400 mg; cohort B, 800 mg; cohort C, 1200 mg; and cohort D, 800 mg every 8 hours × 3 doses [total dose 2400 mg]) with a target serum concentration of at least 2.0 μg/mL for more than 20 hours. Cefixime concentrations from serum and pharyngeal fluid were determined with use of a validated liquid chromatography-tandem mass spectrometry assay. Safety measures included laboratories, physical examinations, and symptom diaries.

RESULTS

None of the single-dose regimens attained the target concentration; however, 50% of subjects in cohort D attained the target concentration. Variation in absorption and protein binding contributed to differences in concentrations. Pharyngeal fluid concentrations were negligible. The single-dose regimens were well tolerated; the multidose regimen resulted in mild to moderate gastrointestinal symptoms in 43% of subjects.

CONCLUSIONS

None of the dosing regimens achieved the target concentration. However, the proposed theoretical target was extrapolated from penicillin data; there are no empirically derived pharmacokinetic/pharmacodynamic criteria for pharyngeal gonorrhea. Under alternative cephalosporin-specific therapeutic goals, the multidose regimen may be effective, although the absence of cefixime in pharyngeal fluid is concerning. A clinical trial evaluating efficacy and defining pharmacokinetic/pharmacodynamic outcomes may be warranted.

Cefixime for Treatment of Maxillary Sinusitis

We evaluated cefixime versus amoxicillin in the treatment of acute or acute exacerbations of chronic maxillary sinusitis in adults. Cefixime 400 mg once daily produced favorable clinical responses in patients compared with amoxicillin 500 mg three times daily. Cefixime appears to be well tolerated with few side effects reported by patients.

Revelation of susceptibility differences due to Hg(II) accumulation in Streptococcus pyogenes against CX-AgNPs and Cefixime by atomic force microscopy

Solution based method for the formation of chemically modified silver nanoparticles (CX-AgNPs) using Cefixime as stabilizing and reducing agent was developed. The CX-AgNPs were characterized by AFM, UV-visible, FT-IR and MALDI-TOF MS. Bactericidal efficiency of CX-AgNPs and Cefixime against Streptococcus pyogenes was evaluated. Afterwards, susceptibility differences of Streptococcus pyogenes due to accumulation of Hg(II) against CX-AgNPs and Cefixime were estimated and validated through Atomic force microscopy. Selectivity and sensitivity of CX-AgNPs against Hg(II) was evaluated in a systematic manner. The CX-AgNPs was titrated against optically silent Hg(II) which induced enhancement in the SPR band of CX-AgNPs. The increase in intensity of SPR band of CX-AgNPs was determined to be proportionate to the concentration of Hg(II) in the range of 33.3-700µM obeying linear regression equation of y = 0.125x + 8.962 with the detection limit of 0.10µM and the coefficient of determination equals to 0.985 (n = 3). The association constant Ka of CX-AgNPs-Hg(II) was found to be 386.0095mol^-1dm³ by using the Benesi Hildebrand plot.

Cephalosporins of the third generation for the treatment of gonorrhea

The article presents the data on antibiotic resistance and N. gonorrhoeae mechanisms for developing resistance to antimicrobial drugs belonging to different pharmacologic groups and applied for causal treatment of gonorrhea. The article proves the key problem related to the treatment of gonococcal infection in Russia lies in the prevalence of strains being resistant to most of the antibacterial drugs that used to be applied in the clinical practice on a broad scale and efficiently. So, cephalosporins of the third generation are presently the only drug type that N. gonorrhoeae remains sensitive to. Their application ensures the maximum efficacy against the gonococcal infection. According to the presentday international recommendations complying with the WHO criteria as well as accumulated experience, cefixime, a drug belonging to cephalosporins of the third generation, can be a drug of choice for the antibacterial therapy of gonorrhea along with ceftriaxon.

Quantitative prediction of oral absorption of PEPT1 substrates based on in vitro uptake into Caco-2 cells

The method for predicting the fraction absorbed (Fa) of the PEPT1 substrates was established based on the in vitro uptake into Caco-2 cells. Uptake of a drug into Caco-2 cells was measured, and the carrier-mediated initial uptake clearance (DeltaCL uptake) was calculated as the difference between the uptake clearance in the absence of glycyl-sarcosine (Gly-Sar) and that in the presence of 30 mM Gly-Sar. The DeltaCL uptake of each drug was then divided by that of cephradine to obtain DeltaCL*uptake, which was a normalized parameter to correct for inter-day and/or inter-cell variability. Then, cephradine (CED), cefixime (CFIX), and cefotiam (CTM) were selected as marker compounds having excellent, medium and poor absorption, respectively. The DeltaCL*uptake and Fa values for CED, CFIX and CTM were fitted to the equation derived from the complete radial mixing (CRM) model, and the scaling factor (A') was obtained. Using the A' value, Fa was predicted from the DeltaCL*uptake value of each drug. Good correlation was observed between the predicted and reported Fa values, which demonstrated that Fa of PEPT1 substrates can be predicted based on the in vitro uptake in Caco-2 cells.

Quantitative relationship between rat intestinal absorption and Abraham descriptors

Literature data on the intestinal absorption of 158 drug and drug-like compounds in rats have been collected, and Abraham descriptors for the set of drugs have been calculated using the method of Platts and Abraham et al. Results show that there is a significant relationship between rat intestinal absorption and the Abraham descriptors. In agreement with the human intestinal absorption model, the dominant descriptors in the rat model are the drug hydrogen bond acidity and basicity. In order to compare the absorption models in humans and rats, the absorption model developed from rats was used to predict the absorption in humans. The rat intestinal absorption model is similar to the human absorption model, and data on rats can effectively be used to predict human intestinal absorption.

PEPT1-mediated cefixime uptake into human intestinal epithelial cells is increased by Ca2+ channel blockers

Ca2+ channel blockers like nifedipine have been shown to increase the oral bioavailability of beta-lactam antibiotics, such as cefixime, in humans. The molecular mode of action of Ca2+ channel blockers on beta-lactam absorption, however, has not yet been defined. Using the Caco-2 human intestinal epithelial cell line, we assessed whether alterations in intracellular free Ca2+ ion (Ca2+in) concentrations by Ca2+ channel blockers or by Ca2+ ionophores affect [14C]cefixime absorption. Reduction of Ca2+in levels by Ca2+ channel blockers (nifedipine, verapamil, diltiazem, or bepridil) at concentrations of 100 microM led to 35 to 50% increases in the cellular uptake of 1 mM [14C]cefixime. Increases in Ca2+in levels by Ca2+ ionophores, on the other hand, led to 40% reductions in [14C]cefixime absorption. Nifedipine increased the V(max) of cefixime transport by 67%, whereas the K(m) of cefixime transport remained unaffected. By measuring the pH in Caco-2 cells loaded with the pH-sensitive fluorescent dye 2',7'-bis(2-carboxyethyl)-5-(6)-carboxyfluorescein, we show that cefixime transport mediated by the intestinal H+-coupled peptide transporter PEPT1 leads to intracellular acidification. This acid load was reduced by nifedipine, although the Ca2+ channel blocker increased the level of H+ and cefixime cotransport. Increases in Ca2+in levels by ionomycin enhanced the decline in intracellular pH induced by cefixime alone, although ionomycin reduced the level of H+ and cefixime cotransport. In conclusion, our studies demonstrate that alterations of Ca2+in levels, e.g., by Ca2+ channel blockers, affect pH regulatory systems, such as apical Na+ and H+ exchange, and thereby alter the H+ gradient that serves as the driving force for uptake of beta-lactams into intestinal epithelial cells.

Oral absorption of cephalosporins is quantitatively predicted from in vitro uptake into intestinal brush border membrane vesicles

In order to establish a method to predict oral absorption of drugs, which are absorbed by the oligopeptide transporter (PepT1), fraction absorbed (F) of cephalosporin antibiotics was predicted from in vitro uptake into rat intestinal brush border membrane vesicles (BBMV). Using in vitro uptake data, F values of cephalosporins in humans were predicted using the equation derived from the complete radial mixing (CRM) model, which was proposed by Amidon et al. (Amidon et al., J. Pharm. Sci. 69 (1980) 1369). In the present study, uptake into BBMV was measured at 25 and 4 degrees C in the presence of an H+ -gradient, and the uptake clearance (CLuptake) was calculated. Clearance for the uptake mediated by PepT1 (DeltaCLuptake) was then calculated as CLuptake at 25 degrees C minus that at 4 degrees C. When DeltaCLuptake and F values were analyzed according to the present equation, fairly good correlation between DeltaCLuptake and F was observed. It was further demonstrated that the present method may be able to quantitatively predict F values of cephalosporins by using several cephalosporins as standards.

Cefixime absorption kinetics after oral administration to humans

Cefixime (CFX) absorption kinetics after oral administration to humans was studied. Four distinct models, incorporating a delay of absorption and first-order elimination kinetics, i.e. first-order absorption (M1), zero-order absorption (M0), Michaelis-Menten type absorption (MM) and Michaelis-Menten type absorption with 'an absorption window' (MM-delta t) were used to fit concentration data of CFX in 10 Chinese men following an oral dose of 400 mg. r2 and AIC were selected as measures of goodness-of-fit. The results show that the MM-delta t model provided a better fit than the other three models. The kinetic parameters were estimated as follows: Vmax' = 10.80 +/- 3.80 mg.l-1.h-1; K(m)' = 88.31 +/- 2.75 micrograms.ml-1; delta t = 4.75 +/- 0.85 h; T1/2 = 4.20 +/- 0.92 h; Tmax = 5.20 +/- 0.92 h; and Cmax = 6.04 +/- 1.70 mg.l-1.

Penetration and bactericidal activity of cefixime in synovial fluid

The penetration of oral cefixime into the synovial fluids of 16 patients (mean age, 50.6 years) who underwent joint taps for rheumatic noninfectious disorders was examined. The patients were each given a single dose (400 mg) 2 to 24 h prior to the tap. Cefixime concentrations in serum and joint fluid samples were measured by high-performance liquid chromatography, and the bactericidal activities of these fluids against three isolates each of Haemophilus influenzae and Escherichia coli were examined. The highest concentrations in serum and synovial fluid were achieved 4 h following drug intake, the mean values being 2.8 and 2.03 micrograms/ml, respectively. Effective bactericidal activities (bactericidal titer, > 1:2) against E. coli and H. influenzae were demonstrated in serum and joint fluid up to 10 h following oral intake of cefixime. These results suggest that cefixime penetrates well into joint fluid, achieving levels above the MIC for E. coli lasting as long as 10 h and levels above the MIC for H. influenzae lasting up to 24 h after administration. Good bactericidal activity against susceptible bacterial isolates was observed for at least 10 h after dosing.

Cefixime. A review of its therapeutic efficacy in lower respiratory tract infections

Cefixime is an orally active third generation cephalosporin with in vitro antibacterial activity against most important lower respiratory pathogens. The drug is active against Haemophilus influenzae, Moraxella catarrhalis and penicillin-susceptible Streptococcus pneumoniae but not Staphylococcus aureus. Cefixime has a long elimination half-life (3 hours compared with 0.5 hours for cefaclor and 1.5 hours for cefalexin), which allows once daily administration. Several trials have established the clinical efficacy of the drug in patients with lower respiratory tract infection (LRTI). In comparative studies cefixime had similar efficacy to amoxicillin +/- clavulanic acid, cefaclor, cefalexin, cefuroxime axetil and clarithromycin. Trials evaluating the efficacy of cefixime as the oral component of intravenous to oral switch therapy have produced promising preliminary results although further carefully designed trials are needed in this area. As with certain other drugs of its class, gastrointestinal disturbances are the most frequently reported adverse events in patients taking cefixime and cases of pseudomembranous colitis have been reported. Thus, cefixime is an effective treatment for mild to moderate LRTI and may have a role as the oral component of intravenous to oral switch therapy although further well designed studies are needed to confirm initial favourable results in this important emerging area of antibacterial therapy.

Oral cephalosporins for use in a parenteral-to-oral switch programme

The advent of the newer cephalosporins has increased the feasibility of parenteral-oral switch programmes within this group of antibacterials. The choice of oral compound is governed by consideration of comparative data on in vitro activity and pharmacokinetics, with particular reference to the antibacterial levels achievable in relevant tissues. The establishment of strict patient criteria and an intensive programme of continuous education of the junior doctors are critical elements in the success of a switch programme. We have continuously audited the implementation, practice and financial results of a parenteral-to-oral switch programme from cefotaxime to cefixime during the past 3 years. Results from this audit finally demonstrated a reversal in the upward trend of cephalosporin expenditures in 1994-95.

Characterization of the oral absorption of some beta-lactams: effect of the alpha-amino side chain group

The intestinal absorption mechanisms of cefixime, 7-aminocephalosporanic acid (7-ACA) and 6-aminopenicillanic acid (6-APA) were determined from the results of single-pass perfusion experiments in rats by modified boundary layer analysis. The estimated absorption parameters (SEM) were as follows: for cefixime, J*max = 0.016 (0.008) mM, Km = 0.031 (0.015) mM, P*m = 0.184 (0.037), P*c = 0.523 (0.051); for 7-ACA, J*max = 6.39 (1.57) mM, Km = 19.33 (5.64) mM, P*c = 0.33 (0.03) mM; and for 6-APA, P*m = 0.41 (0.11), where J*max is the maximal flux of peptide transport system, Km is the intrinsic Michaelis constant, P*m is the dimensionless membrane permeability, and P*c is the dimensionless carrier permeability. Cefixime was absorbed by a carrier-mediated mechanism because its wall permeability (P*w) was concentration dependent and significantly inhibited by cephradine. A concentration-dependent permeability of 7-ACA was observed, but an inhibition study failed to show significant inhibition by cephradine. The absorptions of 6-APA and penicillin V were not inhibited by cephradine or cefixime. The fractions of dose absorbed of several beta-lactam antibiotics correlated well with their absorption numbers obtained from P*w values in rats. These results further demonstrate that an alpha-amino group is not necessary for transport by the intestinal peptide transporter.

Biliary excretion of cefixime: assessment in patients provided with T-tube drainage

The biliary excretion profile of cefixime was studied in 10 patients provided with T-tube drainage of the common bile duct after cholecystectomy. Following a single 200-mg oral dose, the peak concentration of cefixime in bile reached 56.9 +/- 70 mg/liter, approximately 20 times as high as the peak concentration in serum, 2.3 +/- 0.85 mg/liter. Cefixime levels in bile proved relatively sustained, since a concentration of 4.3 +/- 3.7 mg/liter was still found 20 h after dosing. The cumulative amount of cefixime recovered in the 24-h bile drainage averaged 10.0 +/- 12.3 mg, which is 5% of the administered dose and positions this beta-lactam antibiotic among the most highly bile-excreted cephalosporins. The presented results show that a single 200-mg oral dose of cefixime provided drug levels in bile consistently higher than the MICs for the most frequently recovered members of the family Enterobacteriaceae in biliary tract infections and maintained these levels for over 20 h after dosing. Accordingly, this cephalosporin deserves further clinical trials to assess its usefulness in both prophylaxis and treatment of biliary tract infections.

Susceptibility of respiratory tract pathogens in Finland to cefixime and nine other antimicrobial agents

The in vitro activity of cefixime and 9 other orally used antimicrobial agents against 545 selected clinical respiratory tract pathogens was tested using the plate-dilution method. Of the strains tested, 144 were Haemophilus influenzae strains, 151 group A streptococci, 105 pneumococci and 145 Moraxella catarrhalis isolates. Ciprofloxacin was the most active drug, with a minimal inhibitory concentration (MIC) of < 0.06 mg/l for more than 87% of the isolates. With cefixime, a MIC of 0.06 mg/l inhibited 55% of the strains tested and a MIC of 1.0 mg/l inhibited all except one of the 545 strains. One pneumococcal strain was resistant to cefixime. Beta-lactamase producing H. influenzae and M. catarrhalis strains were clearly more susceptible to cefixime than to other oral cephalosporins (cephalexin, cefaclor, cefuroxime). However, penicillin, ampicillin and cefuroxime were more effective against beta-hemolytic streptococci and pneumococci than was cefixime. The new third generation cephalosporin, cefixime, showed markedly better in vitro activity against certain major respiratory tract pathogens than the other peroral antimicrobials commonly used against respiratory tract infections.

Modification of cefixime bioavailability by nifedipine in humans: involvement of the dipeptide carrier system

We studied the action of nifedipine on the bioavailability of cefixime, a molecule absorbed via the gut wall dipeptide carrier system in the rat, and on the bioavailability of D-xylose, which is absorbed via a pH (and Na(+)-)-dependent transporter. Each compound was administered alone or in combination with 20 mg of nifedipine to eight healthy male volunteers. Nifedipine significantly increased the absorption rate of cefixime (20.7 +/- 4.3 versus 16 +/- 3.5 mg/h in the absence of nifedipine). The absolute bioavailability of cefixime alone was 31% +/- 6% compared with 53% +/- 1% (P < 0.01) in the presence of nifedipine. The observed peak concentrations in serum were significantly different (2.5 +/- 0.3 mg/liter without nifedipine and 3.7 +/- 1.1 mg/liter with nifedipine; P < 0.02). In contrast, nifedipine induced no significant differences in the pharmacokinetic profile of xylose following oral administration. We conclude that (i) cefixime is absorbed in humans by an apparently active process which can be enhanced by a calcium channel blocker, in this case, nifedipine; and (ii) nifedipine does not modify the activity of the pentose transporter.

Multiple-dose pharmacokinetics of cefprozil and its impact on intestinal flora of volunteers

The pharmacokinetics of cefprozil were determined with 12 volunteers (8 received cefprozil and 4 received a placebo) after oral administration of 500 mg every 12 h over an 8-day period in a randomized, double-blind, placebo-controlled design. Concentrations in serum and urine were measured by high-pressure liquid chromatography and bioassay. The pharmacokinetic parameters were calculated on the basis of an open one-compartment model. The mean maximum concentration in serum on day 1 was 11.5 +/- 2.6 mg/liter, and the time to reach maximum concentration was 122.3 +/- 30 min after administration. Bioavailability parameters (area under the concentration-time curve from zero to infinity, maximum concentration of the drug in serum, and urinary recovery) indicated an excellent absorption. No accumulation over the 8-day period was registered. Cefprozil had a short biological elimination half-life of 58 +/- 10 min and a renal clearance of 210 +/- 51 ml/min, indicating high rates of renal excretion and tubular secretion. Analysis of the fecal flora showed an ecological impact of cefprozil on the intestinal microflora, such as a moderate decrease in enterobacteria and a slight increase in enterococci, staphylococci, and bacteroides during the study. The number of all bacterial species was already normalized 4 days after the administration period. The tolerance of cefprozil proved to be excellent; only a slight and reversible increase of liver enzymes (in two volunteers), mild cephalalgia, tiredness, and soft stool were registered during the 8-day period. Cefprozil had excellent absorption, no accumulation over an 8-day period, and only a limited impact on the intestinal microflora.

Relationship between renal function and disposition of oral cefixime

The pharmacokinetics of cefixime following a single oral dose of 200 mg have been investigated in 6 normal subjects and in 22 patients with various degrees of renal insufficiency. Serum and urine samples were collected between 0 and 72 h and were subjected to two methods of analysis: bioassay and HPLC. There was a linear relationship between the two sets of results from 228 samples. This result suggests that none of the metabolites, which may accumulate in uraemic patients, has antibacterial activity. In normal subjects, the peak serum level (Cmax) was 2.50 micrograms.ml-1 at 2.83 h (tmax); the apparent elimination half-life (t1/2) was 3.73 h; the apparent total body clearance (CL.f-1) was 154 ml.min-1, the mean renal clearance (CLR) was 39.1 ml.min-1 and the apparent fraction of the dose recovered in 24 h urine was 0.22. In uraemic patients, Cmax and tmax were slightly increased and t1/2 was increased to 12-14 h in patients with an endogenous creatinine clearance below 20 ml.min-1. The apparent volume of distribution was decreased. Apparent total and renal clearances were lower in proportion to the degree of renal insufficiency. Linear relationships were found between CL/f, CLR and creatinine clearance (CLCR). The findings suggest that the dose of cefixime needs to be reduced only in patients with severe renal failure.

[Effectiveness and tolerance of cefixime in the treatment of acute pyelonephritis]

In a prospective, open clinical study, 50 urological patients with acute pyelonephritis were treated with the oral cephalosporin cefixime. The medication (2 x 200 mg/day) was given for seven to ten days. Clinical, bacteriological as well as hematological examinations were carried out prior to, during and immediately after therapy. A late check-up was performed five to nine days after the end of therapy. 46 of the 50 cases were evaluable for efficacy, and all 50 patients were included in safety evaluation. The most frequent pathogens isolated prior to therapy were Escherichia coli (34 times), Proteus mirabilis (six times), Klebsiella pneumoniae (twice) and coagulase-negative staphylococci (twice). Immediately after the end of therapy the pathogens were eradicated in 44 (97.5%) patients. At the late check-up the urine was sterile in 29 (63%) patients. A relapse was observed in 11 patients, a reinfection in four and the initially isolated pathogens had persisted in two. Immediately after the end of therapy 44 (95.7%) patients were clinically cured and two patients had improved. At the late check-up 41 patients were classified as clinically cured, three showed improvement, and two improvement with relapse. Adverse reactions (one case nausea and exanthem, and one case of meteorism) occurred in two patients. No changes in the blood counts or in the liver and kidney functions were observed. In the study described here cefixime proved to be an effective and well tolerated antibiotic for the treatment of upper urinary tract infections; it is of particular interest that 16 of the 50 patients presented with underlying disease favoring infection.

[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.

Cefixime

Cefixime is a new orally active third-generation cephalosporin with a broad spectrum of activity against a variety of both gram-positive and -negative bacteria including many beta-lactamase-producing strains of streptococci, Haemophilus influenzae, Neisseria gonorrhoeae, and the majority of the Enterobacteriaceae. Activity of cefixime against Staphylococcus aureus, enterococci, Listeria monocytogenes, and Pseudomonas spp. is poor. The relatively long elimination half-life of cefixime (approximately 3.0 h) has made possible once- to twice-daily administration with the potential added benefit of improved patient compliance. Clinical trials indicate that cefixime is at least as effective as standard agents in the treatment of genitourinary and upper respiratory tract infections. The incidence of resistant organisms reported during clinical trials with cefixime was low. Adverse reactions observed during clinical trials were relatively uncommon and generally mild and transient in nature. The most significant adverse reactions reported were diarrhea and stool changes occurring in up to 20 percent of patients.

Oral cephalosporins in perspective

Oral cephalosporins, after 25 years of use, continue to present the clinician with a therapeutic challenge. The older agents have been extensively prescribed for ambulatory adult and pediatric patients with a wide variety of infections caused by gram-positive and some gram-negative organisms. The newer agents, cefaclor, cefuroxime axetil, and cefixime, have increased in vitro activity against beta-lactamase-secreting strains of Haemophilus influenzae and Branhamella catarrhalis which has made them more popular for the treatment of otitis media and respiratory tract infections in children. The new agents are also more active against most gram-negative organisms. However, clinical trials have failed to show a clear-cut superiority over older, proven therapy when used to treat infections of the respiratory tract, middle ear, skin and soft tissue, urinary tract, and bone and joints when caused by sensitive organisms. Published reports of clinical trials continue to support the recommendation that oral cephalosporins, especially the newer and more expensive agents, be reserved for second- or third-line therapy when amoxicillin, penicillin V, or trimethoprim/sulfamethoxazole have either failed or produced patient intolerance. Erythromycin/sulfisoxazole and amoxicillin/clavulanate potassium are equally efficacious and also less expensive than cefaclor, cefuroxime axetil, and cefixime and could be considered second-line therapy prior to the use of the newer cephalosporins for infections in the ambulatory patient.

Influence of an antacid containing aluminum and magnesium on the pharmacokinetics of cefixime

Interaction studies in dogs have indicated that antacids significantly decrease the oral bioavailability of cefixime. Twelve healthy adult male volunteers participated in a randomized, four-way crossover trial to evaluate the influence of an aluminum-magnesium antacid (Maalox; 20 ml) on the pharmacokinetics of cefixime (400 mg). Regimens were (i) cefixime alone; (ii) cefixime simultaneous with antacid; (iii) cefixime 2 h before antacid; and (iv) cefixime 2 h after antacid. Serial blood and urine samples were collected over a 24-h period following each dose of cefixime. There was a 1-week washout interval between regimens. Cefixime concentrations in serum and urine were analyzed by high-performance liquid chromatography. Maximum cefixime concentrations in serum for regimens i through iv were (mean +/- standard deviation) 4.9 +/- 1.4, 5.7 +/- 1.3, 5.1 +/- 1.0, and 5.5 +/- 1.5 micrograms/ml, respectively. Corresponding values for area under the serum concentration-time curve extrapolated to infinity were 38.3 +/- 14.5, 42.8 +/- 13.9, 38.5 +/- 9.8, and 41.6 +/- 16.7 micrograms.h/ml. There was a trend toward increased concentrations in serum and area under the curve of cefixime when it was administered concomitantly with antacid; however, these differences were not statistically significant (P greater than 0.05; analysis of variance). We conclude that single-dose administration of an aluminum-magnesium antacid does not significantly decrease the oral bioavailability of cefixime.