Cefaclor uptake by the proton-dependent dipeptide transport carrier of human intestinal Caco-2 cells and comparison to cephalexin uptake.

The human Caco-2 cell line spontaneously differentiates in culture to epithelial cells possessing intestinal enterocytic-like properties. These cells possess a proton-dependent dipeptide transport carrier that mediates the uptake of the cephalosporin antibiotic cephalexin (Dantzig, A.H. and Bergin, L. (1990) Biochim. Biophys. Acta 1027, 211-217). In the present study, the uptake of cefaclor was examined and found to be sodium-independent, proton-dependent, and energy-dependent. The initial rate of D-[3-phenyl-3H]cefaclor uptake was measured over a wide concentration range; uptake was mediated by a single saturable transport carrier with a Km of 7.6 mM and a Vmax of 7.6 nmol/min per mg protein and by a non-saturable component. Uptake was inhibited by dipeptides but not amino acids. The carrier showed a preference for the L-isomer. The effect of the presence of a 5-fold excess of other beta-lactam antibiotics was examined on the initial rates of 1 mM cefaclor and 1 mM cephalexin uptake. Uptake rates were inhibited by the orally absorbed antibiotics, cefadroxil, cefaclor, loracarbef, and cephradine and less so by the parenteral agents tested. The initial uptake rates of both D-[9-14C]cephalexin and D-[3-phenyl-3H]cefaclor were competitively inhibited by cephalexin, cefaclor, and loracarbef with Ki values of 9.2-13.2, 10.7-6.2, and 7.7-6.4 mM, respectively. Taken together, these data suggest that a single proton-dependent dipeptide transport carrier mediates the uptake of these orally absorbed antibiotics into Caco-2 cells, and provide further support for the use of Caco-2 cells as a cellular model for the study of the intestinal proton-dependent dipeptide transporter.

A method for rapid screening of interactions of pharmacologically active compounds with albumin.

We determine the association constants for ligand-protein complex formation using the flow injection method. We carry out the measurements at high flow rates (F=1 mL min(-1)) of a carrier phase. Therefore, determination of the association constant takes only a few minutes. Injection of 1 nM of the ligand (10 µL of 1 µM concentration of the ligand solution) is sufficient for a single measurement. This method is tested and verified for a number of complexes of selected drugs (cefaclor, etodolac, sulindac) with albumin (BSA). We obtain K=4.45×10(3) M(-1) for cefaclor, K=1.00×10(5) M(-1) for etodolac and K=1.03×10(5) M(-1) for sulindac in agreement with the literature data. We also determine the association constants of 20 newly synthesized 3ß- and 3α-aminotropane derivatives with potential antipsychotic activity--ligands of 5-HT1A, 5-HT2A and D2 receptors with the albumin. Results of the studies reported here indicate that potential antipsychotic drugs bind weakly to the transporter protein (BSA) with K≈10(2)-10(3) M(-1). Our method allows measuring K in a wide range of values (10(2)-10(9) M(-1)). This range depends only on the solubility of the ligand and sensitivity of the detector.

Drug therapy in patients undergoing haemodialysis. Clinical pharmacokinetic considerations.

Haemodialysis is utilised therapeutically as supportive treatment for end-stage renal disease (ESRD). In conjunction with haemodialysis therapy, ESRD patients frequently receive a large number of drugs to treat a multitude of intercurrent conditions. Because of the impaired renal function in ESRD patients, dosage reduction is often recommended to avoid adverse drug reactions, particularly for drugs and active metabolites with extensive renal excretion. On the other hand, if the removal of a drug by haemodialysis during concomitant drug therapy is significant, a dosage supplement would be required to ensure adequate therapeutic efficacy. Knowledge of the impact of haemodialysis on the elimination of specific drugs is therefore essential to the rational design of the dosage regimen in patients undergoing haemodialysis. This review addresses the clinical pharmacokinetic aspects of drug therapy in haemodialysis patients and considers: (a) the effects of ESRD on the general pharmacokinetics of drugs; (b) dialysis clearance and its impact on drug and metabolite elimination; (c) the definition of dialysability and the criteria for evaluation of drug dialysability; (d) pharmacokinetic parameters which are useful in the prediction of drug dialysability; and (e) the application of pharmacokinetic principles to the adjustment of dosage regimens in haemodialysis patients. Finally, drugs commonly associated with haemodialysis therapy are tabulated with updated pharmacokinetics and dialysability information.

A pharmacological study of cefaclor in the newborn infant.

The absorption and excretion of cefaclor were studied in 10 newborn infants. A mean peak serum concentration of 7.7 microgram/ml was achieved at 1 hour after an oral dose of 7.5 mg/kg. It is concluded that cefaclor is a well absorbed and tolerated cephalosporin for use in newborn infants.

Concentration of cefaclor in human prostatic tissue.

Concentration of cefaclor, a new oral cephalosporin, was measured in prostatic tissue of ten patients undergoing suprapubic prostatectomy. The average prostatic tissue concentrations were 0.51 +/- 0.22 microgram and 0.74 +/- 0.67 microgram per gram of tissue following the oral administration of 250-milligram and 500-milligram doses, respectively. The prostate/plasma ratios of cefaclor were approximately 0.7 indicating no evidence of accumulation of the drug in prostatic tissue. Levels of cefaclor achieved in human prostatic disease are equal to or less than the minimum inhibitory concentration of strains of known facultative bacterial pathogens associated with prostatitis.

Pharmacokinetic profile of cefaclor.

Cefaclor is a well-absorbed oral cephalosporin antibiotic. Peak concentrations in serum are attained within 30-60 minutes. Food intake reduces the rate, but not the extent of absorption. Cefaclor is not metabolized to a significant degree, but it degrades chemically in the body with an approximate half-life of 2 hours. Most of the drug is excreted unchanged in the urine, the serum half-life after oral administration is 0.5-0.7 hours. Due to the chemical degradation, cefaclor does not accumulate to the same degree as other cephalosporins in case of renal impairment.

Indirect polarographic and cathodic stripping voltammetric determination of cefaclor as an alkaline degradation product.

Cefaclor is not reducible at a mercury electrode, but it can be determined polarographically and by cathodic stripping voltammetry as its initial alkaline degradation product which is obtained in high yield by hydrolysis of cefaclor in Britton-Robinson (B-R) buffer pH 10 at 50 degrees C for 30 min (reduction peak at pH 10, -0.70 V). Differential pulse polarographic calibration graphs are linear up to at least 1 x 10(-4) mol/l(-1). Recoveries of 93% of the cefaclor (n = 3) were obtained from urine spiked with 38.6 microg/ml(-1) using this polarographic method with 1 ml urine made up to 10 ml with pH 10 buffer. Using cathodic stripping voltammetry and accumulating at a hanging mercury drop electrode at - 0.2 V for 30 s, linear calibration graphs were obtained from 0.35 to 40 microg/ml(-1) cefaclor in B-R buffer pH 10. A relative standard deviation of 4.2% (eta = 5) was obtained, and the limit of detection was calculated to be 2.9 ng/ml(-1). Direct determination of cefaclor in human urine (1 ml of urine was made up to 10 ml with pH 10 buffer) spiked to 0.39 microg/ml(-1) was made (recovery 98.6%).

Pharmacokinetics of cefaclor in chronic middle ear effusions.

Fifty children aged 1 to 13 years with chronic or recurrent otitis media with effusion received a single dose of cefaclor (15 mg/kg body weight) by the oral route 30 minutes to seven hours before the removal of middle ear effusion and insertion of tympanostomy tubes. Serum and middle ear aspirate concentrations of the antibiotic were determined employing a microbiological assay technique by a disk diffusion method. Middle ear specimens were also cultured for aerobic bacteria. The mean peak serum concentration level (8.49 +/- 7.89 micrograms/ml) was observed after 30 minutes, whereas the middle ear peak level (0.47 +/- 0.78 micrograms/ml) occurred after one hour. Of the 87 middle ear specimens, 37 had cefaclor concentrations which were detectable within the resolution of the bioassay method (greater than 0.16 micrograms/ml). There was no correlation between the type of middle ear effusion (mucoid or serous) and the concentration of cefaclor in the middle ear. Only 18% of the middle ear cultures were positive for aerobic bacteria; Hemophilus influenzae was the most common organism.

[Phase I clinical studies of S6472 (sustained release preparations of cefaclor)].

Current (regular) preparation of cefaclor (CCL) require the 3-time-a-day administration. S6472 (sustained release preparation) which can be used with the twice-a-day administration in the morning and the evening is capsule and granule preparations consisting of 40% of nonenteric and 60% of enteric coated granules of CCL. Phase I clinical studies of S6472 were conducted in 12 nonfasted healthy adult male volunteers with cross over method using a single dose of 375 mg in capsule and granule forms of S6472, and 250 mg in capsule form of regular CCL as a control drug. The volunteers received the 3 preparations at 1-week interval. The summary of the results from the above studies is as follows: Grouping of the volunteers. The 12 volunteers were divided into 3 groups (each group consists of 4 volunteers) and there were no significant differences between each group regarding background factors of the volunteers. Tolerance. None of the volunteers who received the 3 preparations at 1-week interval complained of subjective abnormalities. No abnormalities which are considered to be due to S6472 and regular CCL were found in the clinical laboratory tests carried out before the administration and 1 week after the completion of the studies. Plasma level. There were no significant differences between capsule and granule forms of S6472 regarding Cmax and AUC, and it was confirmed that bioavailability of both preparations was the same. It was also confirmed that plasma levels of the 2 preparations of S6472 were maintained for longer period of time than those of regular CCL. Urinary excretion. Mean urine levels of the 2 preparations of S6472 every 2 hours after the administration were confirmed to be maintained for longer period of time than those of regular CCL. There were no significant differences between the 2 preparations of S6472 regarding urinary recovery rate. However, the significant differences between the 2 preparations of S6472 and regular CCL were observed. Urinary recovery rate of the 2 preparations of S6472 was 87 approximately 88% of that of regular CCL.

[Absorption and excretion studies of S6472 (sustained release preparations of cefaclor)].

In order to see absorption and excretion of S6472 (sustained release preparations of cefaclor (CCL], 3 studies regarding, 1) influence of meals (single dose of 375 mg in capsule form), 2) dose response (single dose of 375 mg vs. 750 mg in granule form) and 3) continuous administration (twice-a-day administration of 750 mg in granule form for 8 days) were conducted in 15 healthy adult male volunteers using capsule and granule forms of S6472. The following is the summary of the results from the above studies: Tolerance. In the above 3 studies, none of the 15 volunteers complained of subjective abnormalities. In the clinical laboratory tests performed before the administration of S6472 and at the next day of the completion of the studies, the values from the laboratory tests were within normal range. Influence of meals. The average time for peak plasma level of CCL and decrease in the plasma level following the administration of S6472 were the fastest in the fasted volunteers, followed by the volunteers with light meals and usual meals. From this, it was confirmed that plasma levels of CCL were maintained for longer period of time in the non-fasted volunteers than in the fasted volunteers. In the volunteers who had light and usual meals, the peak plasma levels, AUC of the plasma levels and urinary recovery rate were almost the same. Influence by amount of meals was scarcely observed. Dose response. Mean serum levels and their AUC in the volunteers receiving 750 mg of S6472 were approximately twice as much as those in the volunteers receiving 375 mg of S6472, and dose response between the 2 doses was confirmed. Continuous administration. Mean serum levels and their AUC at the first dose and the 15th dose (final dose) were almost the same. In the continuous administration of S6472 for 8 days (15 doses), no accumulation of CCL in the body was observed.

[Cefaclor dosage change with renal dysfunction].

Serum and/or urine levels of cefaclor (CCL) were studied in 4 patients during the therapy with CCL. In patients with severely impaired renal function, moderately higher serum and urine levels of CCL persisted, serum half-lives of CCL were moderately prolonged and urinary excretion of CCL slightly decreased. Although dosage modification of CCL is necessary in patients with renal dysfunction, multiple doses of 250 mg every 8 hours may be safe and effective even in patients with impaired renal function.

[Pharmacological and clinical studies on the long acting cefaclor (S6472)].

A study in which 375 mg of S6472 was orally given to 3 healthy adult volunteers before a meal, after a light meal, and after a usual meal in the cross-over method revealed the highest levels, both in serum and urine, in cases treated before a meal. In cases administered after a light or square meal, the serum level was less, but approximately 2 micrograms/ml over 6 hours after administration. No difference was seen in the AUC. The effective rate of S6472 when given at 750 approximately 1,500 mg/day was 74.6% in 62 patients with skin or soft tissue infectious diseases. Neither subjective or objective adverse reactions were seen in any case. Clinical laboratory testing revealed 1 case each of anemia and increased BUN, for which S6472 was not responsible.

[Clinical studies on te concentration of cefaclor in sera and lung tissues of patients with respiratory diseases].

A 500 mg dose of cefaclor (CCL) was administered orally before surgery to each of patients with respiratory diseases and in fasting. Average concentrations of CCL in sera were 4.04 micrograms/ml at 1.5 hours, 3.03 micrograms/ml at 2 hours, 1.68 microgram/ml at 3 hours and 0.45 microgram/ml at 5 hours after administration. Average concentrations in lung tissues during operation were 0.120 microgram/g at 3 hours, 0.272 microgram/g at 4 hours and 0.297 microgram/g at 5 hours after administration. Ratios of concentrations of CCL in lung tissues to that in sera were from 7.1 to 66.0 percent. The CCL was considered to be a useful antibiotic for the treatment of patients with respiratory diseases.

[Prolonged action preparation of cefaclor].

This study was conducted to develop a prolonged action preparation of cefaclor (CCL) which can offer, with the twice-a-day administration, as much effectiveness as its conventional preparation (Kefral capsule) with the 3 times-a-day administration. Absorption site of CCL in gastrointestinal tract, preparation form (enteric coated granules) which slowly release CCL, dissolution property of the form, and mixed ratio of the form and rapid release form (nonenteric coated granules) were studied and complex granules consisting of 40% of nonenteric coated granules and 60% of enteric coated granules which dissolve at pH 6 were chosen as a prolonged action preparation of CCL. Bactericidal activity of the prolonged action preparation (S6472) was confirmed to be the same as that of the conventional preparation by comparative viable cell count study in which concentrations of CCL simulated to plasma concentrations following the administration of S6472 at the dosage of 375 mg b.i.d. and the conventional preparation at the dosage of 250 mg t.i.d. were used. From the above, S6472 is considered to be a prolonged action preparation of CCL which serve our purpose. Since S6472 can be given with the twice-a-day administration, its daytime administration is not necessary. Therefore, S6472 is considered to be much useful preparation for the patients.

[Fundamental and clinical studies on S6472 (a new prolonged acting preparation of cefaclor) in the urological field].

Fundamental and clinical studies on S6472, a new prolonged acting preparation of cefaclor, were performed and the following results were obtained. Serum level and urinary excretion. 750 mg of S6472, 500 mg of cefaclor (CCL) and 500 mg of cephalexin (CEX) were orally administered in 6 healthy adult volunteers by the cross over method to measure serum level and urinary excretion. The serum level-time curve of S6472 showed 2 peaks at 1 and 6 hours after administration. The peak serum level of S6472 was 4.2 micrograms/ml and 2.9 micrograms/ml, respectively, 1 and 6 hours after administration. The peak serum level of CCL and CEX was 5.8 micrograms/ml and 12.1 micrograms/ml, respectively, 2 hours after administration. The urine level-time curve of S6472 also showed 2 peaks at 0-2 and 4-6 hours after administration and the peak urine level was 1,320 micrograms/ml and 994 micrograms/ml, respectively, 0-2 and 4-6 hours after administration. The peak urine level of CCL was 1,337 micrograms/ml, 0-2 hours after administration and that of CEX was 2,079 micrograms/ml, 2-4 hours. The mean urinary excretion of S6472, CCL and CEX was 56%, 69% and 94% of dose at 12 hours after administration. Clinical evaluation. S6472 was tried in 200 cases of various urinary tract infections. For one group of 85 cases with acute uncomplicated cystitis, clinical effects were evaluated as excellent in 40 cases, moderate in 42 cases and poor in 3 cases, and the overall clinical effectiveness rate was 96.5%. For another group of 68 cases with complicated urinary tract infection, clinical effects were evaluated as excellent in 9 cases, moderate in 27 cases and poor in 32 cases, and the overall clinical effectiveness rate was 52.9%. Side effects. Side effects were observed in 7 cases with diarrhea, epigastralgia, stomatitis, eruption and facial swelling. Administration of S6472 was discontinued in 2 cases, but in 7 cases all symptoms were transient.

[Fundamental and clinical studies of S 6472 (sustained release preparation of cefaclor) in the pediatric field].

Fundamental and clinical studies on S 6472 were carried out and following results were obtained. Serum concentrations after single oral administration showed 2 peaks at 1 or 2 hours and 5 or 6 hours in the cases with normal meal. Namely this drug has much more maintenance of serum concentration than normal cefaclor. In maintenance of serum concentrations after the administration, there were no obviously difference between normal and heavy meal. S 6472 was administered twice a day to 7 patients with various infections (bronchopneumonia 2 cases, acute bronchitis 1 case, purulent tonsillitis 4 cases) and clinical responses were all effective results. Pathogenic bacteria of S. aureus, S. pneumoniae, S. pyogenes and H. influenzae were completely eliminated in all cases. No significant side effects were observed. On the above results, this administration method of S 6472 twice a day was considered to be good response against mild or moderate bacterial infections in children.

Two plate-based colorimetric assays for screening α-amino acid ester hydrolase with high synthesis/hydrolysis ratio.

α-Amino acid ester hydrolases (AEHs) are enzymes of interest to the semi-synthesis of ß-lactam antibiotics with α-amino, such as cephalexin and cefaclor. An undesired side reaction, the hydrolysis of α-amino acid ester, had hindered applications in antibiotics synthesis. Although the enzymes' S/H ratio can be increased by protein engineering, such approaches require a suitable screening assay. Such a screening assay has not yet been described for AEHs. In this paper, we report a 96-well plate format screening procedure for AEHs based on two spectrophotometric assays. To reduce the hydrolysis reaction while maintaining synthesis activity, and to evaluate the effectiveness of the screening strategy, we introduced random mutations in part of the aeh gene from Xanthomonas rubrillineans by error-prone PCR. By a parallel plate-based screening strategy, three mutants with improved S/H ratio, R87L, T132N and N219I, were obtained.