Metabolomic assays of amoxicillin, cephapirin and ceftiofur in chicken muscle: application to treated chicken samples by liquid chromatography quadrupole time-of-flight mass spectrometry.

The aim of this study was to identity metabolites and transformation products (TPs) in chicken muscle from amoxicillin (AMX), cephapirin (PIR) and ceftiofur (TIO), which are antibiotics of the ß-lactam family. Liquid chromatography coupled to quadrupole time-of-flight (QqTOF) mass spectrometry was utilized due to its high resolution, high mass accuracy and MS/MS capacity for elemental composition determination and structural elucidation. Amoxicilloic acid (AMA) and amoxicillin diketopiperazine (DKP) were found as transformation products from AMX. Desacetylcephapirin (DAC) was detected as a metabolite of PIR. Desfuroylceftiofur (DFC) and its conjugated compound with cysteine (DFC-S-Cys) were detected as a result of TIO in contact with chicken muscle tissue. The metabolites and transformation products were also monitored during the in vivo AMX treatment and slaughtering period. It was found that two days were enough to eliminate AMX and associated metabolites/transformation products after the end of administration.

Newly identified degradation products of ceftiofur and cephapirin impact the analytical approach for quantitative analysis of kidney.

This paper describes our research on the degradation of ceftiofur and cephapirin at physiological temperatures in kidney extract and in alkaline and acidic solution, conditions that regularly occur during sample preparation. Degradation products were identified using LC-ToF/MS, NMR and microbiological techniques. Additionally kinetics of the degradation processes were studied. A slight instability of cephapirin and desfuroylceftiofur was observed at elevated temperatures. Ceftiofur and cephapirin degraded immediately and completely in an alkaline environment, resulting in inactive degradation products. Ceftiofur and cephapirin also degraded immediately and completely in kidney extract resulting in both formerly reported metabolites as well as not previously reported products. Our research shows that conditions often occurring during the analysis of ceftiofur or cephapirin result in rapid degradation of both compounds. From this it is concluded that underestimation of the determined amounts of ceftiofur and cephapirin is likely to occur. Therefore, a new approach is needed for the analysis of both compounds newly identified degradation products.

Conversion of cephapirin to deacetylcephapirin in milk and tissues of treated animals.

Cephapirin is one of six beta-lactam antibiotics approved for use in the treatment of food-producing animals in the United States. When used for treatment of mastitis by intramammary infusion, it is partially converted to a microbiologically active metabolite identified as deacetylcephapirin (DACEP). The degradation was followed in four cows with naturally acquired mastitis which were treated with cephapirin. DACEP persisted longer than the parent compound in the milk. When a calf was treated with cephapirin by intramuscular injection, the compound was almost completely converted to DACEP in tissues. The deacetyl form must be considered in the determination of residues in treated animals.

Identification of cephapirin metabolites and degradants in bovine milk by electrospray ionization--ion trap tandem mass spectrometry.

Liquid chromatography-ion trap tandem mass spectrometry (LC-MS/MS) with electrospray ionization was used to identify cephapirin metabolites and degradants in milk from cows dosed with cephapirin. The milk was extracted according to a previously published procedure. Structures for various components were tentatively identified by their molecular weight, product ion mass spectra, and/or correspondence to standard mass spectra. These components may have occurred as metabolites or as degradants that occurred on storage or during extraction. Compounds identified in the milk included cephapirin, desacetylcephapirin, cephapirin lactone, hydrolyzed cephapirin, and a reduced cephapirin lactone that has not previously been reported. Methylcephapirin was also identified, possibly as a trace contaminant in the formulation. Analysis of incurred milk extracts showed that cephapirin and desacetylcephapirin are the major residues in milk. Desacetylcephapirin residues persisted about as long as the parent drug. The detection limit for both residues by LC-MS/MS was approximately 1 ng/mL in milk. These results have implications for microbiological methods or rapid test kits, if such methods or kits respond to cephapirin metabolites and degradants present in the milk.

A review of cephalosporin metabolism: a lesson to be learned for future chemotherapy.

The historical background information concerning the metabolism of cephalosporins and selected other antiinfectives was reviewed as a preface to discussion concerning desacetyl-cefotaxime (dCTX), a metabolite of cefotaxime (CTX) sodium. Cephalothin and cephapirin were metabolized at the 3-position to less active desacetyl forms. However, the parent drugs and their metabolites interact in a favorable manner resulting in dominant additive or synergist inhibition of susceptible bacterial pathogens. Similarly, CTX plus dCTX have been described as being synergist in their activity against greater than 70% of Enterobacteriaceae or staphylococci and greater than 80% of anaerobic bacteria. Antagonism was rare with only two species and of no clinical significance. More recently, reported studies showed enhanced activity of CTX/dCTX against pathogens producing meningitis compared to ceftriaxone and other contemporary therapeutic agents. The dCTX compound was classified as a drug with a potency superior to a "second-generation" cephalosporin and possessed greater beta-lactamase stability against some enzymes compared to CTX. These features may explain low reported rates of superinfections and adverse side-effects, including resistance arising on chemotherapy. Physicians are cautioned to take into account the potential favorable effects of drug metabolites on antimicrobial spectrum, potency and applied pharmacokinetics. In the case of CTX/dCTX, the laboratory results for CTX will always underestimate its value or potency because of the contribution of the metabolite.

Pharmacokinetics and serum concentrations of cephapirin in neonatal foals.

Six healthy foals, from 4 to 6 days of age, were given a single IM injection of sodium cephapirin (250 mg/ml) at a rate of 20 mg/kg of body weight. Serum concentrations of cephapirin were measured serially over an 8-hour period. The mean peak serum concentration was 21.2 micrograms/ml at 10 minutes. The overall elimination rate constant was 1.06/hr and the elimination half-life was 0.70 hour. The apparent volume of distribution at steady state was 1.06 L/kg and plasma clearance was 1,105 ml/hr/kg.

Pharmacokinetics and body fluid and endometrial concentrations of cephapirin in mares.

Six healthy adult horse mares were each given a single injection of sodium cephapirin (20 mg/kg of body weight, IV), and serum cephapirin concentrations were measured serially over a 6-hour period. The mean elimination rate constant was 0.78 hour-1 and the elimination half-life was 0.92 hours. The apparent volume of distribution (at steady state) and the clearance of the drug were estimated at 0.17 L/kg and 598 ml/hour/kg, respectively. Each mare was then given 4 consecutive IM injections of sodium cephapirin (400 mg/ml) at a dosage level of 20 mg/kg. Cephapirin concentrations in serum, synovial fluid, peritoneal fluid, CSF, urine, and endometrium were measured serially. After IM administration, the highest mean serum concentration was 14.8 micrograms/ml 25 minutes after the 4th injection. The highest mean synovial and peritoneal concentrations were 4.6 micrograms/ml and 5.0 micrograms/ml, respectively, 2 hours after the 4th injection. The highest mean endometrial concentration was 2.2 micrograms/g 4 hours after the 4th injection. Mean urine concentrations reached 7,421 micrograms/ml. Cephapirin did not readily penetrate the CSF. When cephapirin was given IM at the same dose, but in a less concentrated solution (250 mg/ml), serum concentrations peaked at 25.0 micrograms/ml 20 minutes after injection, but the area under the serum concentration-time curve was not significantly different (P greater than 0.05). The bioavailability of the drug was greater than or equal to 95% after IM injection.

Depletion of antibiotics from the mammary gland of goats.

Four intramammary infusion products were tested in 10 normal goats to determine their rates of depletion from milk. The products tested, which are marketed for treatment of mastitis in the bovine, contained the single active ingredient erythromycin, oxytetracycline, penicillin, or cephapirin. Each mammary gland was infused, after the goats were milked, with the maximum recommended dose of test product (dosing frequency and quantity) for administration to lactating dairy cattle. With one exception, no antibiotics could be detected in the milk by the end of the bovine milk-discard period. Penicillin was detectable in the milk of one goat for 72 h after the last dose of product containing this antibiotic was given (60-h withdrawal period). Only the product containing oxytetracycline produced significant adverse reactions in the mammary gland. The applicator tips of the products were too large for atraumatic insertion into the teat opening of some goats. Overall, results of this limited study indicated that some intramammary infusion products can be used to treat mastitis in the goat if instructions for use in the bovine are followed.

Retention data for antibiotics commonly used for bovine infections.

This study was designed to observe the maximum time that various antibiotics used in different ways as treatment of bovine infections persisted in milk after final treatment. Both Delvotest-P and Bacillus stearothermophilus (Difco) disc assay procedures were utilized for detection of antibiotic preparations used for treatment of mastitis. None persisted in milk longer than specified on their respective labels. Because antibiotic residues were detected in milk consequent to treatment for intrauterine infections, guidelines for withholding times following intrauterine treatment should be established.

Effect of the ratio of surface area to volume on the penetration of antibiotics in to extravascular spaces in an in vitro model.

The penetration of cephapirin into extravascular spaces of various volumes and ratios of surface area to volume (SA/V) was studied in an in vitro kinetic model. The SA/V ratio was found to be an important determinant of the kinetics of these spaces. The greater the surface area in relation to the volume of the extravascular space, the more closely its kinetics mimicked those of the intravascular space-that is, the higher the absolute peak concentration of drug achieved in the extravascular space, the greater the peak-to-trough fluctuation and the more quickly the peak concentration of drug was reached. Extravascular spaces with similar SA/V ratios demonstrated similar kinetics. Data from various models of extravascular fluid in humans and animals were reviewed, and the kinetics of these extravascular spaces were also found to be determined, at least in part, by the SA/V ratios of the spaces.

A comparison of the penetration characteristics of cephapirin and cephalothin into right atrial appendage, muscle, fat, and pericardial fluid of pediatric patients undergoing open-heart operation.

Thirty-two pediatric patients having open-heart operation received a single dose of either cephalothin or cephapirin intravenously, 30 mg per kilogram of body weight, in the operating room, for prophylaxis before the chest cavity was opened. Samples of right atrial appendage, pericardial fluid, muscle, fat, and plasma were obtained at various time intervals after injection of the antibiotics, and assayed for cephalosporin concentration. The concentration-time profiles of cephalothin and cephapirin in atrial appendage, muscle, fat, and plasma were identical. Cephapirin produced higher total and free concentrations in pericardial fluid compared with cephalothin. This presumably was due to the lower protein binding of cephapirin. Antibiotic concentrations above the minimal inhibitory concentration for Staphylococcus aureus and S. epidermidis were present in myocardial tissue for at least 90 minutes after the dose was administered. These data support the need to administer these antibiotics shortly before surgical intervention and, if the operation is prolonged, the need to administer a second dose of antibiotic.

Pharmacokinetics of cefapirin in patients with normal and impaired renal functions.

The pharmacokinetics of 3-hydroxymethyl-7-[2-(4-pyridyl-thio)acetamido]-2-cephem-2-carboxylic acid acetate (cefapirin) was evaluated after 1.0 g i.m. to 14 patients with different glomerular and tubular functions. Peaks in normal renal function ranged between 9--17 micrograms/ml and was 3--4 times higher in patients with glomerular filtration rates below 30 ml/min. The serum half-life in normal renal function was 0.8 h and was somewhat increased in renal impairment. The distribution volume was little influenced by renal capacity. Recommendations for dosage are given.

Kidney transport of cefapirin in normal and impaired renal function.

The renal transport of cefapirin has been assessed in thirteen patients after one dose of 1.0 g i.m. In normal glomerular filtration rate, approximately 50-60% of the dose is recovered in the urine in active form. The corresponding figure in functions below 30 ml/min was 10-30%. In normal function, tubular secretion accounts for ca. 1/4-1/3 of the amount appearing in the urine.

Concentrations of cephapirin sodium in plasma and gynecologic tissue after a single preoperative dose.

The penetration of cephapirin sodium into tissues that are commonly involved in gynecologic infections was studied after administration of a single i.v. dose of 1 g of cephapirin to about 15 patients to undergo gynecologic surgery. Blood and tissue specimens were obtained either 30 or 60 min after the infusion had been completed. Blood levels averaged 16.07 +/- 3.7 and 6.29 +/- 1.6 microgram/ml and mean tissue levels were 7.87 and 6.28 microgram at these two sampling times, respectively. These results suggest that bactericidal levels of cephapirin against sensitive organisms can be achieved in gynecologic tissues.

A study of the kinetics of cephapirin and cephalexin in pregnancy.

The kinetics of cephapirin and cephalexin were studied in 60 pregnant women after the administration of single 1 g doses of the antibiotics given by the intramuscular and oral route, respectively. Maternal serum, amniotic fluid and cord serum concentrations were measured at intervals after the dose by the agar diffusion method. The results showed that the mean peak concentration of cephalexin in maternal serum, after 1 hour, was significantly greater than that of cephapirin. Both antibiotics crossed the placenta barrier and reached levels in the amniotic fluid and cord serum adequate for the in vitro inhibition of pathogens involved in materno-foetal infections.

Renal excretion of cephapirin and cephaloridine: evidence for saturable tubular reabsorption.

Drug concentrations in plasma and urine were determined in 5 healthy subjects after intravenous infusion of 1 gm cephapirin and cephaloridine. Sampling of blood and urine was frequent and prolonged. Specimens were analyzed by high-pressure liquid chromatography (HPLC). Renal clearance of cephapirin decreased to less than 5% of control in all subjects when drug concentrations in plasma and urine declined. Cephaloridine clearance decreased to a lesser extent. Our findings suggest that, besides tubular secretion and glomerular filtration, a saturable and probably active tubular reabsorption is also involved in the renal handling of these two cephalosporins. The saturable reabsorption process was characterized by its Michaelis-Menten constant Km and its maximum transport capacity Tm.

Bacampicillin, Ampicillin, Cephalothin, and Cephapirin levels in human blood and interstitial fluid.

The diffusibility of bacampicillin, ampicillin, cephalothin, and cephapirin into human interstitial fluid was investigated by using crossover studies. We compared bacampicillin with ampicillin and found that bacampicillin was better absorbed after oral administration. Blood, interstitial fluid, and urine levels were consistently higher in volunteers who received bacampicillin. We compared cephalothin with cephapirin and found that blood and interstitial fluid levels were comparable throughout the study.

Cephapirin concentrations in prostatic and seminal vesicle tissues.

A 15 min i.v. infusion supplying either 1 or 2 g of sodium cephapirin was administered preoperatively to patients about to undergo either retropubic or transvesical prostatectomy. Tissue samples were obtained 30 min after the end of the infusion. Blood samples were obtained immediately before the start of the infusion and 30 min after the end of it. Cephapirin levels in the blood averaged 25.9 +/- 4.0 microgram/ml after the 1 g dose and 47.5 +/- 5.6 microgram/ml after the 2 g dose. Drug levels in prostatic tissue averaged 24.5 +/- 7.1 and 25.8 +/- 4.4 microgram/g for the 1 and 2 g doses, respectively. Levels in tissue taken from the seminal vesicle, often the focus of infection in bacterial prostatitis, averaged 12.5 +/- 2.3 and 44.8 +/- 14.9 microgram/g for the 1 and 2 g doses, respectively. These results suggest that bactericidal levels of cephapirin against sensitive organisms can readily be achieved in the prostate and seminal vesicles.

Effect of cephapirin on formation of D-alanine carboxypeptidase in growing Bacillus subtilis cells.

Cephapirin was utilized to examine the interaction of beta-lactam antibiotics with growing Bacillus subtilis cells and the biological effects simultaneously produced. Saturation binding and quantitative cell death were observed at the cephapirin concentration of 0.1 mug/ml. Cephapirin bound to all penicillin-binding proteins except the d-alanine carboxypeptidase. A specific [(14)C]benzylpenicillin-binding assay was developed for the d-alanine carboxypeptidase. At the lowest saturating concentration of antibiotic (0.1 mug/ml), cephapirin inhibited formation of the d-alanine carboxypeptidase. Upon incubation with cephapirin, 18% of the membranous d-alanine carboxypeptidase was released into the media. The data suggest that beta-lactam antibiotics may affect the formation of bacterial cytoplasmic membranes in addition to their effect on cell wall synthesis.

On the pharmacokinetics of cephalosporin antibiotics.

A review is given on the pharmacokinetic characteristics of some cephalosporin antibiotics. The use of the pharmacokinetic parameters serum concentration, serum protein binding, serum half life, and apparent volume of distribution as a basis for the selection of the clinically most effective cephalosporin derivative is discussed. It is concluded that these parameters must be used in conjunction with data on tissue distribution to specialized sites, and with information on antibacterial activity and toxicity.