Determination of cefaclor by high-performance liquid chromatography

Comparison of the effects of food on the pharmacokinetics of cefprozil and cefaclor

The objective of this study was to assess the effects of food on the pharmacokinetics of cefprozil and cefaclor. A group of 12 healthy male volunteers received a single 250-mg dose of cefprozil or cefaclor under fasting conditions as well as after the intake of food. There was a 1-week washout period between each treatment. Serial blood samples were collected and assayed for cefprozil or cefaclor by specific high-pressure liquid chromatographic methods. The mean +/- standard deviation peak concentration (Cmax) of cefprozil in plasma was 6.13 +/- 1.22 micrograms/ml under the fasting condition and 5.27 +/- 1.06 micrograms/ml after breakfast, and these values were not significantly different from each other. The corresponding median time to reach Cmax was prolonged after food intake, but this difference was not significant. The mean Cmax values of cefaclor decreased significantly from 8.70 +/- 2.72 micrograms/ml under the fasting condition to 4.29 +/- 1.52 micrograms/ml after breakfast, and the corresponding median times to reach Cmax were significantly prolonged. The mean half-lives of cefprozil and cefaclor were nearly identical for the two treatments, suggesting that the elimination kinetics of these cephalosporins remained unaltered when the drugs were administered with food. The area under the plasma-concentration-versus-time curves for fasted and fed conditions were not significantly different for both drugs. The results of this study indicate that the extent of absorption and rate of elimination of both cephalosporins remain unaltered in the presence of food. However, the absorption rate of cefaclor is significantly reduced in the presence of food, while that of cefprozil remains unaltered. As a result, the Cmax of cefaclor is significantly reduced in the presence of food, whereas that of cefprozil is not significantly affected. Cefprozil can be administered with a meal without markedly affecting levels in blood.

Phase I study of multiple-dose cefprozil and comparison with cefaclor

The objectives of this study were to assess the safety and tolerance of cefprozil, to characterize the pharmacokinetics of cefprozil after administration of multiple doses of the drug, and to compare these pharmacokinetic parameters with those obtained with cefaclor. The volunteers received 28 doses of 250, 500, or 1,000 mg of cefprozil or 500 mg of cefaclor every 8 h for 10 days. Serial blood samples and the total volume of urine voided by each individual were collected for pharmacokinetic evaluation on days 1, 5, and 10. Both cephalosporins were well tolerated after multiple oral dosing. The peak levels in plasma (Cmax) of cefprozil ranged from 5.7 to 18.3 micrograms/ml after oral administration of 250- to 1,000-mg doses. The regression analysis of Cmax on cefprozil dose showed a dose-linear response. The mean Cmax of cefaclor ranged from 15.2 to 16.7 micrograms/ml and did not change significantly on multiple dosing. The overall mean terminal half-life of cefprozil was 1.2 h and was invariant with respect to dose or duration of dosing. The area under the plasma-concentration-versus-time curve from 0 h to infinity (AUC0-infinity) of cefprozil increased in a dose-proportional manner with an increase in dose. The overall urinary recovery (61% of dose) and renal clearance values of cefprozil were generally invariant with respect to dose and duration of dosing. While cefprozil was apparently absorbed less rapidly and achieved lower Cmax values than cefaclor, the AUC0-infinity of cefprozil was nearly twofold greater than that of cefaclor. The half-life of cefprozil was also twofold longer than that observed for cefaclor. Although the urinary recovery of cefaclor (75% of dose) was significantly higher than that of cefprozil (61% of dose), the concentrations of cefprozil in urine remained significantly higher than those of cefaclor from 2 to 8 h postdosing. If the therapeutic concept is maintained that levels of beta-lactam antibiotics in plasma should exceed the MIC for the offending organisms over a period that approximates the dosing interval, then cefprozil would appear to be suitable for twice-daily administration, whereas cefaclor should probably be administered three or even four times a day.

Comparison of cefprozil and cefaclor pharmacokinetics and tissue penetration

The pharmacokinetics and tissue penetration, as judged by skin blister fluid, of cefprozil and cefaclor were examined in 12 healthy male volunteers. Doses of 250 and 500 mg of each drug were given to fasting subjects in a crossover fashion. Serially obtained plasma, skin blister fluid, and urine samples were analyzed for cefprozil or cefaclor by validated high-pressure liquid chromatographic methods. After oral administration of 250 and 500 mg of cefprozil, mean concentrations in plasma rose to peak levels (Cmax) of 6.1 and 11.2 micrograms/ml, respectively, and those of cefaclor were 10.6 and 17.3 micrograms/ml, respectively. The elimination half-life of cefprozil (1.3 h) was significantly longer than that of cefaclor (0.6 h), and as a result, the area under the curve for cefprozil was about two times greater than that for cefaclor. Both cephalosporins were primarily excreted unchanged in urine. The mean skin blister Cmax values were 3.0 and 5.8 micrograms/ml for cefprozil and 3.6 and 6.5 micrograms/ml for cefaclor after the 250- and 500-mg oral doses, respectively. The mean Cmax values in skin blister fluid for both cephalosporins were comparable and were significantly lower than the corresponding Cmax values in plasma. However, the levels of cefprozil and cefaclor in skin blister fluid declined more slowly than they did in plasma. The skin blister fluid half-life estimates for cefprozil were significantly longer than they were for cefaclor. Parallel to the observation in plasma, the mean skin blister fluid areas under the curve for cefprozil were significantly higher than they were for cefaclor. The plasma and skin blister fluid pharmacokinetic analyses suggest that the exposure of humans to cefprozil is significantly greater than that to cefaclor at the same dose.

Recent analytical methods for cephalosporins in biological fluids

Since 1980, RP chromatography has been the principal analytical technique used for cephalosporins. This technology offers selectivity, accuracy, and ease of use. Most of the methods rely on protein precipitation and, to a lesser extent, solid-phase isolation or extraction procedures. The proper selection of a method depends on the analytical constraints imposed by the overall objective of the study. For example, pharmacokinetic datum interpretation mandates that the method be validated and provide specific and accurate results. LC is the preferred technique, since it not only meets these specifications but may also distinguish between the drug and metabolites. Those chromatographic methods which quantify several different cephalosporins are not desirable for pharmacokinetic datum interpretation, since accuracy and precision are usually compromised in order that many different drugs may be quantified in a single analysis. The proper selection of sample preparation method is dependent on the presence of potential interferences and the acceptable lower limit of quantitation. Protein precipitation methods offer ease of sample preparation but may suffer from nonselectivity. Solid-phase isolation and extraction procedures may increase selectivity and improve the limit of quantitation. Although LC provides specific and accurate results, clinical laboratories may prefer to use the less specific methods for therapeutic drug monitoring. In this case, microbiological, enzymatic, and fluorimetric methods offer improved sample throughput but less specificity. However, these methods should not be used for drugs that may have a low margin of safety or if the patient is on multiple-antibiotic therapy. Future methods may involve incorporating solid-phase isolation columns to enhance the specificity of chromatographic, microbiological, enzymatic, and fluorescence methods. Advancements in microbore column technology may allow improvements in the selectivity and sensitivity of LC methods. Many investigators prefer to use simple protein precipitation procedures for sample preparation because of sample throughput constraints. However, advances in robotic sample preparation may allow the more cumbersome solid-phase isolation or extraction techniques to be used to improved sample throughput and specificity.

Antibiotic monitoring in body fluids

Analytical procedures recently described for the quantitative determination of antibiotics in body fluids are reviewed. High-performance liquid chromatography (HPLC) and immunoassays appear as an alternative to current microbiological assays. HPLC has been applied to most antibiotics in clinical use and a major part of the review deals with this technique. Attention is given to sample pretreatment, characteristics of chromatography and detection, and limit of sensitivity. Non-isotopic immunoassays have been essentially applied to aminoglycosides and vancomycin and are also reviewed. Advantages and drawbacks of HPLC and immunoassays are presented.

Determination of a new orally active cephalosporin in human plasma and urine by high-performance liquid chromatography using automated column switching

A sensitive method for the determination of a new cephalosporin in human serum and urine is described. The sensitivity of the procedure is derived from a high-performance liquid chromatographic separation which utilizes the different selectivities of two columns. Partial separation of the agent from deproteinized serum or diluted urine is achieved by an anion-exchange column. To concentrate the large volume of the eluent fraction containing the compound from the anion-exchange column, a reversed-phase short column is placed between the anion-exchange column and a reversed-phase analytical column. The separation is completed by switching the eluent fraction containing the compound from the second column to the analytical column. The compound is detected by ultraviolet absorption at 295 nm. Quantitation is possible down to 0.05 microgram/ml using 300 microliter of serum and down to 0.5 microgram/ml using 50 microliter of urine. The coefficients of variation of the method are 6.8% and 0.6% in serum when spiked at the 0.05 microgram/ml and 1.0 microgram/ml level, respectively. One assay can be completed in 16 min. Serum levels and urinary excretion data obtained with this method are given for three healthy volunteers who had received a 100-mg oral dose of the compound.

Decreased absorption of cefaclor in short bowel syndrome

Oral cefaclor is rapidly absorbed in patients with a shortened gastrointestinal tract (23 cm). A case is reported of a 27-month-old female child who had received oral cefaclor for five days in treatment of otitis media. The child had had a bowel resection at birth. She did not respond to oral therapy with cefaclor and was admitted to the hospital, where she received cefamandole intramuscularly. The patient recovered in five days. Further investigation using cefaclor with this patient demonstrated serum concentrations below the minimum inhibitory concentration of Hemophilus influenzae, pneumococcus, and many other organisms. When oral antibiotics are prescribed, it is necessary to monitor serum concentrations to ensure absorption.