The bioavailability of cefpodoxime proxetil tablets relative to an oral solution

The bioavailability of cefpodoxime proxetil tablets relative to an oral solution of cefpodoxime proxetil in a sucrose/alcohol/citric acid vehicle was studied in 11 healthy volunteers in a randomized, crossover study. Fasted subjects took one cefpodoxime proxetil 100 mg tablet or 50 mL of a 2 mg mL^?1 cefpodoxime proxetil oral solution on two separate occasions. In a third study period, all subjects took a 100 mg dose of the oral solution with a high-fat meal to investigate the effect of food on cefpodoxime proxetil absorption from the oral solution. Serial blood samples were obtained over a 24h period, and urine was collected for 48h after dosing. Cefpodoxime concentrations in plasma and in urine were determined using HPLC methods. The bioavailability of cefpodoxime proxetil tablets relative to the oral solution was 82%, as determined from AUC ratios. There was no difference in the rate of cefpodoxime absorption between dosage forms. Food had no effect on the extent of drug absorption from the oral solution but did result in delayed absorption. These results suggest that complete dissolution of cefpodoxime proxetil is critical for optimal bioavailability.     

Investigation of factors responsible for low oral bioavailability of cefpodoxime proxetil

Learning about the behavior of a drug in biological environment enables application of better formulation strategies to improve bioavailability of the same. Cefpodoxime proxetil (CP) is a prodrug, which is orally administered cephalosporin with only 50% absolute bioavailability. Despite previous studies, reasons responsible for low bioavailability of CP remain poorly understood. The present study tries to ascertain reasons for the low oral bioavailability of CP. The in vitro, in situ and ex vivo studies showed interesting results, where metabolism of CP into cefpodoxime acid (CA) inside the intestinal epithelial cell and preferential efflux of CA into lumen was identified as primary reason for low oral bioavailability of CP. Presence of specific carriers or transportation mechanism on the apical side membrane of enterocyte, than basal side of the same was observed.     

头孢泊肟酯片的人体相对生物利用度研究

目的 :比较国产与进口头孢泊肟酯片在正常人体内的药动学与相对生物利用度。方法 :2 4名男性健康志愿者随机交叉单次口服国产或进口头孢泊肟酯片 2 0 0mg后 ,采用反相高效液相色谱法测定血药浓度 ,用 3P97软件包计算两者的药动学参数与相对生物利用度。结果 :国产片和进口片口服吸收的药 时曲线符合一室模型。Tmax分别为 (2 .5±s0 .6 )h和 (2 .3± 0 .5 )h ,Cmax为 (3.5± 0 .6 )mg·L- 1和 (3.6± 0 .5 )mg·L- 1,AUC0 t分别为 (18± 3)mg·L- 1和 (18.0± 2 .8)mg·L- 1,AUC0 ∞ 分别为(19± 3)mg·L- 1和 (19± 3)mg·L- 1,T12 Ke分别为(2 .0± 0 .3)h和 (2 .2± 0 .4 )h。国产片相对于进口片的相对生物利用度为 (10 2± 15 ) %。经方差分析及双单侧t检验 ,各药动学参数无显著差异 (P >0 .0 5 )。结论 :国产片与进口片生物等效。     

Investigation on physicochemical and biological differences of cefpodoxime proxetil enantiomers.

Cefpodoxime proxetil (CP) is a prodrug of cefpodoxime acid (CA), and is supplied as racemic mixture of R- and S-enantiomers. CP has only 50% absolute bioavailability, and the reasons responsible for low bioavailability remain poorly understood. The present work ascertains physicochemical and biological properties of individual isomers of CP and explores their capacity to optimize delivery of CP. Both isomers showed similar pH stability behavior, but R-isomer was more susceptible to enzymatic metabolism compared to S-isomer, when incubated with enzymes collected from various segments of GIT. Based on the in vitro and in vivo results, use of S-isomer for development of a dosage form such as gastro-retentive dosage form can improve oral bioavailability of CP.     

Effect of oil-in-water submicron emulsion surface charge on oral absorption of a poorly water-soluble drug in rats

The effect of oil-in-water submicron emulsion (SE) droplet surface charge on absolute bioavailability of a poorly water-soluble drug (griseofulvin, as model drug) after oral administration was studied in conscious rat. Positively, negatively, and neutrally charged SE were designed and characterized (size, polydispersity index, zeta potential, and pH). Three emulsion formulations, whose compositions included 40% oil phase and differed only in the nature of the emulsifying agent, were retained. Only the positively charged SE showed a higher area under the plasma concentration-time curve (AUC(0 --> infinity)) in comparison with the tablet and with the other SE.     

Effect of Oil-in-Water Submicron Emulsion Surface Charge on Oral Absorption of a Poorly Water-Soluble Drug in Rats

The effect of oil-in-water submicron emulsion (SE) droplet surface charge on absolute bioavailability of a poorly water-soluble drug (griseofulvin, as model drug) after oral administration was studied in conscious rat. Positively, negatively, and neutrally charged SE were designed and characterized (size, polydispersity index, zeta potential, and pH). Three emulsion formulations, whose compositions included 40% oil phase and differed only in the nature of the emulsifying agent, were retained. Only the positively charged SE showed a higher area under the plasma concentration–time curve (AUC_{0 → ∞}) in comparison with the tablet and with the other SE.     

头孢泊肟酯片和颗粒人体相对生物等效性试验研究

目的研究国产头孢泊肟酯片及颗粒与进口头孢泊肟酯片在24名男性健康志愿者体内的生物等效性。方法采用标准3制剂、3周期的二重3×3拉丁方式自身对照试验设计,24例男性健康志愿受试者单剂量口服国产头孢泊肟酯颗粒（受试制剂A）、头孢泊肟酯片（受试制剂B）和进口头孢泊肟酯片（参比制剂R）。药物血清质量浓度以高效液相色谱法测量,药代动力学参数采用3P97和ndst21w软件处理。结果头孢泊肟酯受试制剂A、受试制剂B和参比制剂R的达峰时间（Tmax）分别为（2.81±0.51）h,（2.85±0.54）h,（2.92±0.52）h,峰浓度（Cmax）分别为（3.44±0.93）μg/mL,（3.32±0.74）μg/mL,（3.47±0.80）μg/mL,0～12h药时曲线下面积（AUC0-12h）分别为（20.02±5.61）μg·h/mL,（19.28±4.23）μg·h/mL,（19.59±5.18）μg·h/mL。受试制剂A和受试制剂B对参比制剂R的相对生物利用度分别为103.16%和100.65%。结论 3种头孢泊肟酯制剂在人体内具有生物等效性。     

Cefpodoxime proxetil. A review of its antibacterial activity, pharmacokinetic properties and therapeutic potential.

Cefpodoxime proxetil is an orally administered prodrug which is absorbed and de-esterified by the intestinal mucosa to release the third generation cephalosporin, cefpodoxime. Cefpodoxime is stable towards the most commonly found plasmid-mediated beta-lactamases and the drug has a broad spectrum of antibacterial activity encompassing both Gram-negative and Gram-positive bacteria, rendering it a possible option for empirical use in a wide range of community acquired infections in both adult and paediatric patients. The extended plasma half-life of cefpodoxime (1.9 to 3.7 h) permits twice daily administration. In comparative trials, twice daily cefpodoxime proxetil (dose equivalent cefpodoxime 100 to 400 mg) was as effective as a 3- to 4-times daily regimen of phenoxymethylpenicillin in pharyngotonsillitis, as well as thrice daily amoxicillin (with or without clavulanic acid) or cefaclor against infections of the ear, the upper and lower respiratory tract, the urinary tract and those of the skin and soft tissues. The latter reflects the enhanced antistaphylococcal activity of cefpodoxime, which distinguishes it from other orally active third generation cephalosporins such as cefixime. Most notably, an oral regimen of cefpodoxime proxetil was as efficacious as parenterally administered ceftriaxone for the treatment of bronchopneumonia in hospitalised patients at risk due to the presence of underlying diseases, addictions or advancing age. A single oral dose of cefpodoxime was also as efficacious as ceftriaxone in uncomplicated anogenital gonococcal infections. Cefpodoxime proxetil is generally well tolerated, with mild to moderate gastrointestinal disturbances occurring in 4 to 15% of patients treated with therapeutic doses. Thus, a convenient twice daily oral regimen of cefpodoxime proxetil can be prescribed as an effective alternative to established beta-lactam therapies in the empirical outpatient treatment of infections of the respiratory and urinary tracts as well as those of the skin and soft tissues.     

Bioavailability of diazepam from aqueous-organic solution, submicron emulsion and solid lipid nanoparticles after rectal administration in rabbits.

The bioavailability of diazepam in rabbits after rectal administration of three formulations: organic-aqueous Relsed rectal solution (containing ethanol, benzyl alcohol and propylene glycol), submicron emulsion and solid lipid nanoparticles (SLN), was studied. Submicron emulsion contained MCT oil (20% w/w), egg lecithin and poloxamer; SLN were prepared with cetyl palmitate 10% w/v and non-ionic emulsifying agent, Plantacare. All formulations contained 4 mg/ml of diazepam and the dose administrated to rabbits was 2 mg/kg. In both submicron preparations nearly the same mean size of the dispersed particles (201-206 nm) and the fraction of the free drug in aqueous phase (0.9-1.5%) was determined. Besides very moderate prolongation of drug release, the submicron emulsion as a vehicle did not alter pharmacokinetics of diazepam when compared with the solution: the mean C(max) was 48.9+/-24.0 and 49.5+/-17.0 ng/ml, and area under the curve was 134.0+/-42.3 and 186.8+/-59.8 ng h/ml, for solution and emulsion, respectively. The low relative bioavailability, 47% compared to the solution, was observed after administration of SLN. Transmission electron microscopy pictures revealed that some of diazepam is present on the surface of the SLN and this fraction was immediately absorbed, while the diffusion of the drug in the solid core was not efficient enough to allow a complete release. It may be concluded that submicron emulsion may be a good choice of an ethanol-free drug formulation, but lipid matrix, which is solid at body temperature, is not advantageous system for diazepam rectal delivery, even if delivered as a submicron dispersion.     

Cerebrospinal fluid pharmacokinetics of cefpodoxime proxetil in piglets

Cefpodoxime is an oral third-generation cephalosporin used for the treatment of acute upper-respiratory tract infections caused by susceptible bacteria in children. Although not indicated for the treatment of bacterial meningitis, it is used to treat other infections produced by organisms associated with meningitis and may obscure the result of cerebrospinal fluid (CSF) cultures in children who develop meningitis while receiving oral antibiotics if sufficient concentrations are achieved in the CSF. This study evaluated the disposition of cefpodoxime and penetration into CSF in piglets. Fifteen Landacre-Camborough cross piglets (10-20 days old) received cefpodoxime proxetil oral suspension (10 mg/kg). Repeated plasma and CSF samples were collected over 24 hours for quantitation of cefpodoxime by HPLC. Pharmacokinetic analysis was performed on both plasma and CSF data. The plasma concentration versus time data for cefpodoxime were best characterized using a one-compartment model with first-order absorption. The mean (+/- SD) pharmacokinetic parameters for Cmax, tmax, and AUC0-infinity were 23.3 +/- 12.9 mg/L, 3.9 +/- 1.4 h, and 237 +/- 129 mg/L.h, respectively. CSF/plasma ratios for AUC0-infinity demonstrated a mean cefpodoxime penetration of approximately 5%. CSF penetration of cefpodoxime was evident following a single oral dose of cefpodoxime proxetil suspension. Despite the small percentage of total cefpodoxime dose distributing into the CSF, the resultant concentrations approached or exceeded the MIC90 for many bacterial pathogens considered susceptible to cefpodoxime. Accordingly, clinicians should use caution in the interpretation of CSF cultures in patients who develop clinical signs and symptoms consistent with meningitis and who have been previously treated with cefpodoxime.     

Cefpodoxime proxetil: a review of its use in the management of bacterial infections in paediatric patients

Cefpodoxime proxetil is an oral third generation cephalosporin with a broad spectrum of antibacterial activity. The drug has in vitro activity against many common Gram-positive and Gram-negative pathogens associated with common paediatric infections, making the drug a useful option for empirical therapy. In randomised controlled trials conducted in children with acute otitis media, oral cefpodoxime proxetil 8 to 10 mg/kg/day (usually administered in 2 divided doses) for 5 to 10 days was at least as effective as standard regimens of amoxicillin/ clavulanic acid, cefixime, cefuroxime axetil or cefaclor as assessed by either clinical or bacteriological criteria. Cefpodoxime 8 to 10 mg/kg/day (administered in 2 divided doses) for 5 to 10 days was at least as effective as standard 10-day regimens of penicillin V in the treatment of children with pharyngitis and/or tonsillitis. Significant differences in favour of cefpodoxime proxetil were demonstrated in terms of clinical (1 study) and bacteriological (2 studies) criteria. The clinical efficacy of 5 days of treatment with cefpodoxime proxetil is similar to that of 10 days of treatment with penicillin V. In children with lower respiratory tract infections (primarily pneumonia), clinical and bacteriological efficacy rates achieved with cefpodoxime proxetil treatment were similar to those produced by cefuroxime axetil or amoxicillin/clavulanic acid in randomised controlled trials. Cefpodoxime proxetil also demonstrated clinical efficacy in paediatric patients with skin and soft tissue infections. In randomised studies that included both adults and children with a variety of infections (e.g. abscess, atheroma, furuncle and carbuncle, infected wounds, cellulitis), cefpodoxime proxetil showed efficacy similar to that of cefuroxime axetil or cefaclor. Cefpodoxime proxetil is well tolerated by paediatric patients, with adverse events (primarily gastrointestinal tract disturbances and skin rashes) that are consistent with those reported for other oral cephalosporins. CONCLUSION: Cefpodoxime proxetil is a third generation cephalosporin with a broad spectrum of antibacterial activity and a favourable pharmacokinetic profile which allows twice-daily administration. It is generally well tolerated and demonstrates good bacteriological and clinical efficacy in paediatric patients with various infectious diseases, including acute otitis media, tonsillitis and/or pharyngitis. Based on these characteristics, cefpodoxime proxetil is a suitable option for the treatment of paediatric patients with various common bacterial infections.     

Miotic effect and irritation potential of pilocarpine prodrug incorporated into a submicron emulsion vehicle.

Pilocarpine prodrug, O,O'-dipivaloyl(1,2-ethylene) bispilocarpic acid diester, was introduced to a submicron emulsion vehicle in a dose equivalent to 0.5% pilocarpine base, and the formulation was studied in albino rabbits using miotic assay. Compared with pilocarpine HCl 0.5% solution delayed and prolonged miosis was observed after application of the prodrug emulsion. AUC(0-6 h) values for the prodrug emulsion and pilocarpine solution were 9252+/-1345 and 6845+/-1967%xmin, respectively. The prodrug was also administered twice daily for 5 days in the form of aqueous solution or submicron emulsion in order to study ocular irritation. Irritation potential of the prodrug was significantly reduced when submicron emulsion was used as a vehicle. Copyright     

头孢泊肟酯片人体相对生物利用度和生物等效性

目的:考察头孢泊肟酯片受试制剂和参比制剂的人体相对生物利用度,并评价两者的生物等效性。方法:22名健康男性志愿者随机交叉单剂量口服头孢泊肟酯片受试制剂200mg和参比制剂200mg,用HPLC法测定给药后血浆样本中头孢泊肟的浓度,用DAS软件计算其药动学参数,并评价两种制剂的相对生物利用度。结果:受试制剂和参比制剂的tmax分别为(2.6±0.6)和(2.9±0.7)h,Cmax分别为(2.9±0.8)和(3.4±0.6)mg.L-1,t1/2分别为(2.4±0.6)和(2.14±0.23)h,AUC0-t分别为(16.1±4.0)和(18.2±3.6)mg.h.L-1,AUC0-∞分别为(17.0±3.9)和(19.1±3.7)mg.h.L-1。受试制剂的相对生物利用度F0-tn和F0-∞分别为(88.6±15.6)%、(89.8±14.7)%。结论:两种制剂具有生物等效性。     

AS-924, a novel, orally active, bifunctional prodrug of ceftizoxime: physicochemical properties, oral absorption in animals, and antibacterial activity.

AS-924 is an oral prodrug of the antibiotic ceftizoxime (CTIZ), a parenteral use cephalosporin. This novel prodrug, produced by esterifying CTIZ with a lipophilic pivaloyloxymethyl (POM) group and introducing a water soluble L-alanyl group, is expected to increase the bioavailability and thereby, augment the antibacterial activity of CTIZ in vivo compared with existing prodrugs. To study the effect of the L-alanyl group in AS-924 on its bioavailability, the plasma concentration profiles of CTIZ in dogs were examined following the dosing of AS-924 and CTIZ-POM, in powder form, after pretreatment with the antacid ranitidine, and following the dosing of AS-924 after pretreatment with a gastrointestinal motility stimulant metoclopramide or suppressant scopolamine butylbromide. The absorption rate of AS-924 was constant under these different conditions due to its unique balance of lipophilicity and water solubility. CTIZ is as antibacterially active as pre-existing oral cephalosporins against Gram-positive clinical isolates, while being more active against all Gram-negative isolates-particularly Enterobacteriaceae and Haemophilus influenzae. A simulation model for the eradication profile of bacteria in computer programmed pharmacokinetic (PK) system was carried out to study the antibacterial action of CTIZ in human. CTIZ was proven to eradicate Streptococcus pneumoniae and H. influenzae effectively, while cefpodoxime (CPOD), the active moiety of CPOD proxetil, eradicated S. pneumoniae, but not H. influenzae. These results confirm that, AS-924 is a potent oral antibiotic and would be expected to be clinically effective and efficient.     

Cefpodoxime proxetil. An appraisal of its use in antibacterial cost-containment programmes, as stepdown and abbreviated therapy in respiratory tract infections

Cefpodoxime proxetil is an orally administered prodrug which is converted in vivo to the third generation cephalosporin cefpodoxime. Cefpodoxime has a similar spectrum of antibacterial activity to the parenteral cephalosporins ceftriaxone and cefotaxime and a long elimination half-life, which allows once- or twice-daily administration. Cefpodoxime proxetil has proven efficacy in the treatment of community-acquired pneumonia and upper respiratory tract, skin and soft tissue and urinary tract infections. It has been evaluated for use in cost-containment programmes, as stepdown (parenteral-to-oral conversion) therapy in the treatment of community-acquired pneumonia and as abbreviated therapy in upper respiratory tract infections. Substituting oral for parenteral therapy can achieve considerable savings (in acquisition, delivery and labour costs). Moreover, oral administration has advantages for the patient in terms of comfort and mobility, avoids the hazards of parenteral delivery and may allow earlier discharge from hospital, or even allow home treatment from the outset in low-risk patients. As hospitalisation is usually the major cost component in treating serious infections, considerable savings can be made in this way. Pharmacy-driven stepdown programmes in 2 US hospitals have achieved cost savings by targeting patients with community-acquired pneumonia for early conversion from intravenous ceftriaxone therapy to oral cefpodoxime proxetil. Costs were compared with those from a control group of patients who continued to receive intravenous ceftriaxone until physicians deemed that oral therapy (with various agents) was appropriate. In one study, duration of parenteral therapy in the cefpodoxime proxetil group was reduced from 6.18 to 3.82 days and duration of hospitalisation was reduced from 10.06 to 6.23 days (p < 0.02), with corresponding hospitalisation cost reductions of $US7300 per patient. However, clinical trial data relating to the efficacy of cefpodoxime proxetil as stepdown therapy in patients initially requiring parenteral antibacterials are lacking. Abbreviated (4-to 7-day) cephalosporin regimens appear to be as effective as traditional 10-day penicillin regimens in the treatment of upper respiratory tract infections. Short regimens may improve patient compliance and tolerability, thereby reducing the costs of adverse effects and treatment failures. Data from preliminary clinical studies suggest that a 5-day course of cefpodoxime proxetil is as effective as an 8-day course of amoxicillin/clavulanic acid in treating either acute otitis media or sinusitis, and as effective as a 10-day course of amoxicillin/ clavulanic acid and more effective than a 10-day course of phenoxymethyl- penicillin in the treatment of pharyngotonsillitis. Cefpodoxime proxetil tended to be better tolerated and was associated with better compliance than penicillin-based regimens. Indeed, a pharmacoeconomic study showed that a 10-day regimen of cefpodoxime proxetil was associated with lower costs for treating adverse effects and treatment failures than a 10-day regimen of amoxicillin/clavulanic acid in the treatment of acute otitis media in children. A 5-day course of cefpodoxime proxetil had a lower cost per patient treated per month free of recurrence than a 10-day course of phenoxymethylpenicillin (non-generic) or amoxicillin/clavulanic acid in the treatment of recurrent pharyngotonsillitis. Thus, evidence to date suggests that cefpodoxime proxetil has potential for use as stepdown therapy in community-acquired pneumonia and in abbreviated therapy courses in upper respiratory tract infections. These preliminary observations require confirmation in well designed studies.     

Characterization of impurities in cefpodoxime proxetil using LC–MSn

Reversed-phase liquid chromatography coupled with electrospray ionization tandem mass spectrometry (ESI-MS/MS) was used to characterize impurities in cefpodoxime proxetil, an ester-modified prodrug. Based on the mechanisms by which cephalosporins are degraded, stress tests were designed and performed. The bulk material and capsule were eluted through a C18 column with formic acid–methanol–water as the mobile phase. In total, 15 impurities were characterized in commercial samples, including 7 known impurities and 8 new impurities. The structures of these unknown compounds were deduced via comparison with the fragmentation patterns of cefpodoxime proxetil. Data from this systematic study will help improve the safety and quality of cefpodoxime proxetil.Key words: Cefpodoxime proxetil, Cephalosporins, Impurities, LC–MS, Structure identification     

水飞蓟宾口服亚微乳剂的制备及大鼠体内药动学研究

目的:制备水飞蓟宾口服亚微乳并研究其在大鼠体内的药动学。方法:采用薄膜分散-探头超声法制备水飞蓟宾亚微乳。大鼠分别灌服水林佳(市售水飞蓟宾磷脂复合物胶囊)和水飞蓟宾亚微乳,于不同时间点取血,HPLC法测定血药浓度,采用DAS(Date Acquisition System)软件求算药动学参数。结果:水飞蓟宾亚微乳制剂的平均粒径为(155.9±2.2)nm,Zeta电位为-(29.62±0.03)mV,体外释放动力学符合Weibull方程;大鼠灌服水林佳和水飞蓟宾亚微乳后MRT分别为(1.73±0.03)h和(3.44±0.08)h,AUC0-∞分别为(1.83±0.38)mg·h·L-1和(4.72±0.48)mg·h·L-1。水飞蓟宾亚微乳的相对生物利用度为257.9%。结论:水飞蓟宾制成亚微乳制剂后延长了药物在体内的滞留时间,提高了药物的口服生物利用度。     

Preparation & characterization of solid inclusion complex of cefpodoxime proxetil with beta-cyclodextrin

Cefpodoxime proxetil (CPDX-PR) is an oral cephalosporin antibiotic with poor aqueous solubility and bioavailability. Effect of beta-cyclodextrin on aqueous solubility and dissolution rate of cefpodoxime proxetil was evaluated by the formation of solid inclusion complexes in 1:2 molar ratio of drug: cyclodextrin. Phase solubility study was carried out whereby a typical B's type curve was obtained thus, indicating a 1:2 stoichiometric ratio for optimum complex formation. Solid inclusion complexes in 1:2 molar ratios were prepared by using methods such as physical mixture, solvent evaporation and freeze drying. Prepared complexes were characterized by fourier transform infrared spectroscopy (FT-IR) differential scanning calorimetry (DSC), powder x-ray diffraction (PXRD) and scanning electron microscopy (SEM). Results of in vitro studies appraised of an increased solubility and dissolution rate of cefpodoxime proxetil on complexation with beta- cyclodextrin (P < 0.05) as compared to CPDX-PR alone. Amongst the complexes prepared by different methods, the complex prepared by freeze drying showed the highest dissolution rate (P< 0.01). The in vitro antimicrobial activity of cefpodoxime proxetil and its freeze dried complex (1:2) was studied against both antibiotic-susceptible and antibiotic-resistant clinical isolates of Neisseria gonorrhoeae. The freeze dried complex (1:2) inhibited all penicillin-susceptible strains and penicillinase-producing strains at 0.015 microg/ml concentration. Chromosomally resistant strains which were not responsive to penicillin were inhibited by the complex at 0.125 microg/ml concentration. The study revealed that complexation of cefpodoxime proxetil with beta-cyclodextrin effectively enhanced the aqueous solubility and in vitro antibacterial activity.     

In vivo evaluation of tablets and capsules containing spray-dried o/w-emulsions for oral delivery of poorly soluble drugs

It is recognised that poorly soluble drugs may show an increased oral bioavailability when incorporated in o/w-emulsions. Encapsulating the emulsion lipid droplets in hydroxypropyl methylcellulose (HPMC) by spray drying has been demonstrated to preserve an improved bioavailability releasing lipid droplets from the powder in vivo. However, the spray-dried powder is cohesive and bulky requiring additional processing to improve handling. This was resolved in previous work where a directly compressible dry emulsion formulation was described. The purpose of the present study is to investigate the oral bioavailability resulting from administration of a directly compressible dry emulsion as a tablet and compare it with a HPMC dry emulsion powder and a simple lipid solution. Four female Beagle dogs received a single dose of each formulation containing the same amount of medium-chain triglycerides (MCT) and a model drug, Lu 28-179. Cyclodextrin solutions administered orally and intravenously were used as references. The absolute bioavailability decreased in the order cyclodextrin solution (0.14), HPMC dry emulsion (0.11), technically improved dry emulsion (0.10) and MCT solution (0.06). The directly compressible dry emulsion tablets were concluded to be comparable to a HPMC dry emulsion powder in terms of bioavailability. The lack of statistically significant differences relative to a MCT solution was ascribed to a low and variable absolute oral bioavailability of the model drug.     

RU 29 246, the active compound of the cephalosporin prodrug-ester HR 916. III. Pharmacokinetic properties and antibacterial activity in vivo.

The pharmacokinetics of the broad spectrum cephem RU 29 246 and its prodrug-ester HR 916 B were investigated in mice, rats and dogs and compared to those of cefpodoxime proxetil, cefuroxime axetil and cefixime. HR 916 B is well absorbed following oral administration and efficiently converted to the antibacterially active form. In mice, mean peak blood levels of 31.1 micrograms/ml of the parent compound were recorded within 20 minutes after oral administration of a single dose equivalent to 40 mg/kg RU 29 246. The bioavailability calculated on the basis of the areas under the concentration-time curves (AUC) and the urinary recoveries was about 90%. In rats, peak blood levels of 14.5 micrograms/ml were obtained 1 hour after an oral 20 mg/kg dose. The bioavailability was calculated as 70%. In dogs, 40% of an oral 10 mg/kg dose was recovered in the urine within 24 hours. Cmax was 15.9 micrograms/ml at 4.6 hours. Mean elimination half-lives of RU 29 246 were 0.35, 0.5 and 2.1 hours in mice, rats and dogs, respectively. After an oral HR 916 B dose equivalent to 50 mg/kg of RU 29 246, tissue concentrations at 0.5 hour ranged between 0.8 micrograms/g in brain and 95.7 micrograms/g in murine kidneys. These values of HR 916 B are similar to, or distinctly higher than, those of the reference compounds. Of the oral cephalosporins tested, HR 916 B had the most balanced antibacterial spectrum. With ED50s of between 0.9 and 11.5 mg/kg against staphylococci, its activity was similar to that of the additional reference compound cefaclor and higher than that of cefuroxime. Cefixime and cefpodoxime proxetil displayed low antistaphylococcal activity or were inactive. In septicemias with Enterobacteriaceae, cefixime and cefpodoxime proxetil were more potent than HR 916 B and cefaclor. Cefuroxime axetil was inactive against most of these infections. HR 916 B was also highly effective against murine lung infections caused by Klebsiella pneumoniae DT-S or Streptococcus pneumoniae 1147.