Comparative pharmacokinetics of YM-13115, ceftriaxone, and ceftazidime in rats, dogs, and rhesus monkeys

Effect of ketoprofen and tolfenamic acid on intravenous pharmacokinetics of ceftriaxone in sheep

In this study, the pharmacokinetics of ceftriaxone (40 mg/kg) was determined following a single intravenous (IV) administration of ceftriaxone alone and co-administration with ketoprofen (3 mg/kg) or tolfenamic acid (2 mg/kg) in sheep. Eight healthy Akkaraman sheep (2.4 ± 0.3 years and 44 ± 4 kg of body weight) were used. The study was carried out according to the longitudinal design in three periods with a 15-day washout period between administrations. In the first period, sheep received ceftriaxone alone via an IV injection. In the second and third periods, the same sheep received ceftriaxone in combination with ketoprofen and tolfenamic acid, respectively. Plasma concentrations of ceftriaxone were assayed by high-performance liquid chromatography and analyzed using non-compartmental analysis. Following the administration of ceftriaxone alone, the elimination half-life (t_1/2ʎz ), area under the plasma concentration-time curve from zero (0) hours to infinity (∞) (AUC_0-∞ ), total clearance (Cl_T ), and volume of distribution at steady state were 1.42 h, 182.41 h*µg/ml, 0.22 L/h/kg, and 0.17 L/kg, respectively. While ketoprofen and tolfenamic acid significantly increased the t_1/2ʎz and AUC_0-∞ of ceftriaxone, they significantly reduced the Cl_T . Ceftriaxone (40 mg/kg, IV) in concurrent use with ketoprofen and tolfenamic acid can be administrated at the 12 h dosing intervals to maintain T> minimum inhibitory concentration (MIC) values above 60% in the treatment of infections caused by susceptible pathogens with the MIC value of ≤0.75 and ≤1 μg/mL, respectively, in sheep with an inflammatory condition.

Pharmacokinetics of ceftriaxone in freshwater crocodiles (Crocodylus siamensis) after intramuscular administration at two dosages

One of the major obstacles to the successful treatment of infectious disease in freshwater crocodile species is incorrect dosing of antibiotics. There are few reports on pharmacokinetics and dosage regimens of antimicrobial drugs in crocodiles. The purpose of the present study was to clarify the pharmacokinetic characteristics of ceftriaxone (CEF) in Siamese freshwater crocodiles (Crocodylus siamensis). Freshwater crocodiles, Crocodylus siamensis, in breeding farms were treated with a single intramuscular administration of CEF at two dosages, 12.5 and 25 mg/kg body weight (b.w.). Blood samples were collected at preassigned times up to 168 hr. The plasma concentrations of CEF were measured by a validated method through liquid chromatography tandem-mass spectrometry. CEF plasma concentrations were quantified up to 72 and 96 hr after low- and high-dose administration, respectively. The C_max values of CEF were 24.61 ± 5.15 µg/ml and 26.39 ± 2.81 µg/ml at dosages of 12.5 and 25 mg/kg b.w., respectively. The AUC_last values increased in a dose-dependent fashion. The half-life values were not statistically different between the groups (around 20 hr). The average binding percentage of CEF to plasma protein was 53.78 ± 2.11%. Based on the pharmacokinetic data, susceptibility break-point and the surrogate PK-PD index (T > MIC, 0.2 μg/ml), i.m. administration of CEF at a dose of 12.5 mg/kg b.w. might be appropriate for initiating treatment of susceptible bacterial infections in freshwater crocodiles.

Network pharmacology for antiepileptogenesis: Tolerability and neuroprotective effects of novel multitargeted combination treatments in nonepileptic vs. post-status epilepticus mice

Network-based approaches in drug discovery comprise both development of novel drugs interacting with multiple targets and repositioning of drugs with known targets to form novel drug combinations that interact with cellular or molecular networks whose function is disturbed in a disease. Epilepsy is a complex network phenomenon that, as yet, cannot be prevented or cured. We recently proposed multitargeted, network-based approaches to prevent epileptogenesis by combinations of clinically available drugs chosen to impact diverse epileptogenic processes. In order to test this strategy preclinically, we developed a multiphase sequential study design for evaluating such drug combinations in rodents, derived from human clinical drug development phases. Because pharmacokinetics of such drugs are known, only the tolerability of novel drug combinations needs to be evaluated in Phase I in öhealthy" controls. In Phase IIa, tolerability is assessed following an epileptogenic brain insult, followed by antiepileptogenic efficacy testing in Phase IIb. Here, we report Phase I and Phase IIa evaluation of 7 new drug combinations in mice, using 10 drugs (levetiracetam, topiramate, gabapentin, deferoxamine, fingolimod, ceftriaxone, α-tocopherol, melatonin, celecoxib, atorvastatin) with diverse mechanisms thought to be important in epileptogenesis. Six of the 7 drug combinations were well tolerated in mice during prolonged treatment at the selected doses in both controls and during the latent phase following status epilepticus induced by intrahippocampal kainate. However, none of the combinations prevented hippocampal damage in response to kainate, most likely because treatment started only 16-18 h after kainate. This suggests that antiepileptogenic or disease-modifying treatment may need to start earlier after the brain insult. The present data provide a rich collection of tolerable, network-based combinatorial therapies as a basis for antiepileptogenic or disease-modifying efficacy testing.

Comparison of the Pharmacokinetic Profiles of Ceftriaxone Used Alone and Combined with Danhong Injection in Old Rats

BACKGROUND AND OBJECTIVES

Danhong injection is the most commonly prescribed adjuvant drug applied for the treatment of cardiovascular and cerebrovascular diseases in China. Ceftriaxone is usually prescribed along with Danhong injection to elderly patients with complications. However, the pharmacokinetic interactions between these two medications have not been investigated. The aim of this study was to investigate whether Danhong injection influences the pharmacokinetic profile of ceftriaxone in old rats when these two medications are used in combination.

METHODS

The animal experiment protocol was designed according to the clinical data. Ten-month-old male Sprague-Dawley (SD) rats were dosed with ceftriaxone through intravenous administration for 1 or 7 days in the presence or absence of Danhong injection. The combinations were divided into 1-day, 7-day, and 14-day combined-treatment groups in which Danhong injection was administered for 1, 7, or 14 days and ceftriaxone was given for 1, 7, or 7 days, respectively. The plasma concentration of ceftriaxone was determined by ultrahigh performance liquid chromatography coupled with triple-quadrupole mass spectrometry (UHPLC-TQ-MS) on a BEH C18 column with a mobile phase consisting of acetonitrile and 0.4% formic acid-water. The chromatographic method was validated and found to be simple, rapid, and stable.

RESULTS

Danhong injection significantly increased the plasma clearance of and decreased systemic exposure to ceftriaxone. In the 1-day combined-treatment group, the plasma clearance of ceftriaxone increased by 52.69%, and the area under the concentration-time curve (AUC) of ceftriaxone was decreased by 32.54% (P < 0.01). In the 7-day combined-treatment group, the rate of plasma clearance increased by 52.49% and the area under the concentration-time curve decreased by 31.15% (P < 0.01). For the 14-day combined-treatment group, the plasma clearance of ceftriaxone increased by 26.73%, and the area under the concentration-time curve decreased by 21.44% (P < 0.05).

CONCLUSIONS

In old male rats, systemic exposure to ceftriaxone decreased when used concomitantly with Danhong injection, which may be because Danhong injection increased the plasma clearance of ceftriaxone. Further investigations should be carried out to clarify the mechanism for the influence of Danhong injection on the pharmacokinetics of ceftriaxone.

Pharmacokinetics of ceftriaxone in Green sea turtles (Chelonia mydas) following intravenous and intramuscular administration at two dosages

Green sea turtles are widely distributed in tropical and subtropical waters. Adult green sea turtles face many threats, primarily from humans, including injuries from boat propellers, being caught in fishing nets, pollution, poaching, and infectious diseases. To the best of our knowledge, limited pharmacokinetic information to establish suitable therapeutic plans is available for green sea turtles. Therefore, the present study aimed to describe the pharmacokinetic characteristics of ceftriaxone (CEF) in green sea turtles, Chelonia mydas, following single intravenous and intramuscular administrations at two dosages of 10 and 25 mg/kg body weight (b.w.). Blood samples were collected at assigned times up to 96 hr. The plasma concentrations of CEF were measured by liquid chromatography tandem mass spectrometry. The concentrations of CEF in the plasma were quantified up to 24 and 48 hr after i.v. and i.m. administrations at dosages of 10 and 25 mg/kg b.w., respectively. The C_max values of CEF were 15.43 ± 3.71 μg/ml and 43.48 ± 4.29 μg/ml at dosages of 10 and 25 mg/kg, respectively. The AUC_last values increased in a dose-dependent fashion. The half-life values were 2.89 ± 0.41 hr and 5.96 ± 0.26 hr at dosages of 10 and 25 mg/kg b.w, respectively. The absolute i.m. bioavailability was 67% and 108%, and the binding percentage of CEF to plasma protein was ranged from 20% to 29% with an average of 24.6%. Based on the pharmacokinetic data, susceptibility break-point and PK-PD index (T > MIC, 0.2 μg/ml), i.m. administration of CEF at a dosage of 10 mg/kg b.w. might be appropriate for initiating treatment of susceptible bacterial infections in green sea turtles.

Critical analysis of treatment trials of rhesus macaques infected with Borrelia burgdorferi reveals important flaws in experimental design

A critical analysis of two treatment trials of Chinese rhesus macaques infected with Borrelia burgdorferi indicates that insufficient attention was placed on documenting the blood levels, pharmacokinetics, and pharmacodynamic parameters of the antibiotics used in this host. Consequently, it is impossible to conclude that the findings have validity in judging the efficacy of doxycycline or ceftriaxone for the treatment of Borrelia burgdorferi in this animal model.

Persistence of Borrelia burgdorferi in rhesus macaques following antibiotic treatment of disseminated infection

The persistence of symptoms in Lyme disease patients following antibiotic therapy, and their causes, continue to be a matter of intense controversy. The studies presented here explore antibiotic efficacy using nonhuman primates. Rhesus macaques were infected with B. burgdorferi and a portion received aggressive antibiotic therapy 4–6 months later. Multiple methods were utilized for detection of residual organisms, including the feeding of lab-reared ticks on monkeys (xenodiagnosis), culture, immunofluorescence and PCR. Antibody responses to the B. burgdorferi-specific C6 diagnostic peptide were measured longitudinally and declined in all treated animals. B. burgdorferi antigen, DNA and RNA were detected in the tissues of treated animals. Finally, small numbers of intact spirochetes were recovered by xenodiagnosis from treated monkeys. These results demonstrate that B. burgdorferi can withstand antibiotic treatment, administered post-dissemination, in a primate host. Though B. burgdorferi is not known to possess resistance mechanisms and is susceptible to the standard antibiotics (doxycycline, ceftriaxone) in vitro, it appears to become tolerant post-dissemination in the primate host. This finding raises important questions about the pathogenicity of antibiotic-tolerant persisters and whether or not they can contribute to symptoms post-treatment.

Chronokinetics of ceftazidime after intramuscular administration to dogs

Ceftazidime, a third-generation cephalosporin, is widely used for the treatment of Pseudomonas aeruginosa infections. The aims of the present study were to characterize the pharmacokinetics of ceftazidime and to estimate the T > MIC against P. aeruginosa, after its intramuscular (i.m.) administration at two different dosing times (08:30 h and 20:30 h) to dogs, in order to determine whether time-of-day administration modifies ceftazidime pharmacokinetics and/or predicted clinical antipseudomonal efficacy. Six female healthy beagle dogs were administered ceftazidime pentahydrate by the intramuscular route in a single dose of 25 mg/kg at both 08:30 and 20:30 h, two weeks apart. Plasma ceftazidime concentrations were determined by microbiological assay. Pharmacokinetic parameters and time above the minimum inhibitory concentration (T > MIC) and 4xMIC for Pseudomonas aeruginosa were calculated from the disposition curve of each dog. No differences between the daytime and nighttime administrations were found for the main pharmacokinetic parameters, including C(max), t(max), t((1/2) lambda), AUC, and MRT; however, the high interindividual variability shown by these values and the small number of individuals may account for this lack of difference. Rate of absorption (k(a)) was significantly higher after the 20:30 h than 08:30 h administration. No significant differences between T > MIC were found when comparing the 08:30 h and 20:30 h administrations. Mean T > MIC values predicted a favorable bacteriostatic effect for all susceptible strains of P. aeruginosa for the 12 h dosing interval at both dosing times. Our results suggest that similar antipseudomonal activity may be expected when ceftazidime is administered at 8:30 and 20:30 h; however, as only two timepoints of drug administration were explored, we are unable to draw any conclusions for other treatment times during the 24 h.

Pharmacokinetic parameters of ceftriaxone after single intravenous and intramuscular administration in camels (Camelus Dromedarius)

The purpose of this study was to investigate the plasma disposition kinetics of ceftriaxone in female camels (n=5) following a single intravenous (i.v.) bolus or intramuscular (i.m.) injections at a dosage of 10mg kg(-1) body weight in all animals. A crossover design was carried out in two phases separated by 15 days. Jugular blood samples were collected serially for 48h and the plasma was analysed by high-performance liquid chromatography (HPLC). Following single i.v. injections the plasma concentration time curves of ceftriaxone were best fitted to a two-compartment model. The drug was rapidly distributed with half-life of distribution t(1/2alpha) of 0.24+/-0.01h and moderately eliminated with elimination rate constant and elimination half-life of 0.27+/-0.13h(-1) and 2.57+/-0.52h, respectively. The volume of distribution at steady state (V(dss)) was 0.32+/-0.01lkg(-1) and the total body clearance (Cl(tot)) was 0.11+/-0.01lkg(-1)h(-1), respectively. Following i.m. administration, the mean T(max), C(max), t(1/2el) and AUC values for plasma data were 1.03+/-0.23h, 21.54+/-2.61microg ml(-1), 1.76+/-0.03h and 85.82+/-11.21microg ml(-1)h(-1), respectively. The i.m. bioavailability was 93.42+/-21.4% and the binding percentage of ceftriaxone to plasma protein was moderate, ranging from 33% to 42% with an average of 34.5%.

Pharmacokinetics of ceftazidime after intravenous and intramuscular administration to domestic cats

The pharmacokinetic properties of ceftazidime, a third generation cephalosporin, were investigated in five cats after single intravenous (IV) and intramuscular (IM) administration at a dose rate of 30 mg/kg. Minimum inhibitory concentrations (MICs) of ceftazidime for some Gram-negative (Escherichia coli, n=11) and Gram-positive (Staphylococcus spp., n=10) strains isolated from clinical cases were determined. An efficacy predictor, measured as the time over which the active drug exceeds the bacteria minimum inhibitory concentration (T>MIC), was calculated. Serum ceftazidime disposition was best fitted by a bi-compartmental and a mono-compartmental open model with first-order elimination after IV and IM dosing, respectively. After IV administration, distribution was rapid (t(1/2(d)) 0.04+/-0.03 h), with an area under the ceftazidime serum concentration:time curve (AUC((0-infinity))) of 173.14+/-48.69 microg h/mL and a volume of distribution (V((d(ss)))) of 0.18+/-0.04 L/kg. Furthermore, elimination was rapid with a plasma clearance of 0.19+/-0.08 L/hkg and a t(1/2) of 0.77+/-0.06 h. Peak serum concentration (C(max)), T(max), AUC((0-infinity)) and bioavailability for the IM administration were 89.42+/-12.15 microg/mL, 0.48+/-0.49 h, 192.68+/-65.28 microg h/mL and 82.47+/-14.37%, respectively. Ceftazidime MIC for E. coli ranged from 0.0625 to 32 microg/mL and for Staphylococcus spp. from 1 to 64 microg/mL. T>MIC was in the range 35-52% (IV) and 48-72% (IM) of the recommended dosing interval (8-12h) for bacteria with a MIC(90)4 microg/mL.

Pharmacokinetics of ceftriaxone after intravenous, intramuscular and subcutaneous administration to domestic cats

The pharmacokinetic properties of ceftriaxone, a third-generation cephalosporin, were investigated in five cats after single intravenous, intramuscular and subcutaneous administration at a dosage of 25 mg/kg. Ceftriaxone MICs for some gram-negative and positive strains isolated from clinical cases were determined. Efficacy predictor (t > MIC) was calculated. Serum ceftriaxone disposition was best fitted by a bicompartmental and a monocompartmental open models with first-order elimination after intravenous and intramuscular and subcutaneous dosing, respectively. After intravenous administration, distribution was fast (t1/2d 0.14 +/- 0.02 h) and moderate as reflected by the volume of distribution (V(d(ss))) of 0.57 +/- 0.22 L/kg. Furthermore, elimination was rapid with a plasma clearance of 0.37 +/- 0.13 L/h.kg and a t1/2 of 1.73 +/- 0.23 h. Peak serum concentration (Cmax), tmax and bioavailability for the intramuscular administration were 54.40 +/- 12.92 microg/mL, 0.33 +/- 0.07 h and 85.72 +/- 14.74%, respectively; and for the subcutaneous route the same parameters were 42.35 +/- 17.62 microg/mL, 1.27 +/- 0.95 h and 118.28 +/- 39.17%. Ceftriaxone MIC for gram-negative bacteria ranged from 0.0039 to >8 microg/mL and for gram-positive bacteria from 0.5 to 4 microg/mL. t > MIC was in the range 83.31-91.66% (10-12 h) of the recommended dosing interval (12 h) for Escherichia coli (MIC90 = 0.2 microg/mL).

Pharmacokinetics, Urinary and Mammary Excretion of Ceftriaxone in Lactating Goats

The pharmacokinetic properties of ceftriaxone were investigated in 10 goats following a single intravenous (i.v.) and intramuscular (i.m.) administration of 20 mg kg(-1) body weight. After i.v. injection, ceftriaxone serum concentration-time curves were characteristic of a two-compartment open model. The distribution and elimination half-lives (t(1/2alpha), t(1/2beta)) were 0.12 and 1.44 h respectively. Following i.m. injection, peak serum concentration (C(max)) of 23.6 microg ml(-1) was attained at 0.70 h. The absorption and elimination half-lives (t(1/2ab), t(1/2el)) were 0.138 and 1.65 h respectively. The systemic bioavailability of the i.m. administration (F %) was 85%. Following i.v. and i.m. administration, the drug was excreted in high concentrations in urine for 24 h post-administration. The drug was detected at low concentrations in milk of lactating goats. A recommended dosage of 20 mg kg(-1) injected i.m. every 12 h could be expected to provide a therapeutic serum concentration exceeding the minimal inhibitory concentrations for different susceptible pathogens.

Species-specific uncertainty factors for compounds eliminated principally by renal excretion in humans

An uncertainty factor of 100 is used to derive health-based guidance values for human intakes of chemicals based on data from studies in animals. The 100-fold factor comprises 10-fold factors for species differences and for interindividual differences in response. Each 10-fold factor can be subdivided into toxicokinetic and toxicodynamic aspects with a 4.0-fold factor to allow for kinetic differences between test species and humans. The current work determined the extent of interspecies differences in the internal dose (toxicokinetics) of compounds which are eliminated primarily by renal excretion in humans. An analysis of the published data showed that renal excretion was also the main route of elimination in the test species for most of the identified probe substrates. Interspecies differences were apparent for both the mechanism of renal excretion (glomerular filtration, tubular secretion and/or reabsorption) and the extent of plasma protein binding, both of which may affect renal clearance and therefore the magnitude of species differences in the internal dose. For compounds which are eliminated unchanged by both humans and the test species, the average differences in the internal doses between humans and animals were 1.6 for dogs, 3.3 for rabbits, 5.2 for rats and 13 for mice. This suggests that for renal excretion, the differences between humans and the rat and especially the mouse may exceed the 4.0-fold default factor for toxicokinetics.

Prediction of human pharmacokinetics from animal data and molecular structural parameters using multivariate regression analysis: volume of distribution at steady state

The aim of this study was to develop a regression equation for predicting volume of distribution at steady state (Vd(ss)) in humans to enable application to various types of drugs using animal experimental data for rats and dogs and some molecular structural parameters. The Vd(ss) data for rats, dogs and humans of 64 drugs were obtained from literature. The compounds have various structures, pharmacological activities and pharmacokinetic characteristics. In addition, the molecular weight, calculated partition coefficient (clogP), and the number of hydrogen bond acceptors were used as possible descriptors related to the Vd(ss) in humans. Multivariate regression analyses, multiple linear regression analysis and the partial least squares (PLS) method were used to predict Vd(ss) in humans. Interaction terms were also introduced into the regression analysis to evaluate the non-linear relationship. For the data set used in the present study, PLS with quadratic term descriptors gave the best predictive performance. The PLS model using Vd(ss) data for only two animal species and using easily calculated structural parameters could generally predict Vd(ss) in humans better than an allometric method. In addition, the PLS model with only animal data gave almost the same predictive performance as the PLS model with quadratic term descriptors. This model may be easier to use and be practical in a realistic situation, and could predict Vd(ss) in humans better than the allometric method.

Daily variations in ceftriaxone pharmacokinetics in rats

The aim of this study was to determine whether the time of day ceftriaxone was administered modified its pharmacokinetics. Ceftriaxone was given intraperitoneally at either 0400, 1000, 1600, and 2200 h to Sprague-Dawley rats synchronized under a light-dark cycle of 12 h of light and 12 h of dark. Pharmacokinetic parameters were analyzed for the presence of a 24-h rhythm. Results showed significant daily variations (P < 0.05) in ceftriaxone clearance, with the highest values during the dark phase. It is concluded that time-dependent variations in ceftriaxone pharmacokinetics may affect the therapeutic efficacy of current once-daily dosing schedules.

Prediction of human clearance from animal data and molecular structural parameters using multivariate regression analysis

The aim of the study reported here was to develop a method for predicting human clearance that can be applied to various kinds of drugs using clearance values for rats and dogs and some molecular structural parameters. The clearance data for rats, dogs, and humans of 68 drugs were obtained from literature. The compounds have various structures, pharmacological activities, and pharmacokinetic characteristics. In addition, molecular weight, c log P, and the number of hydrogen bond acceptors were used as possible descriptors related to the human clearance value for each drug. Three types of regression methods, multiple linear regression (MLR) analysis, partial least squares (PLS) method, and artificial neural network (ANN), were used to predict human clearance, and their predictive performances were compared with allometric approaches, which have been widely used in interspecies scaling. In MLR and PLS analyses, interaction terms were introduced to evaluate the nonlinear relationships. For the data sets used in the present study, MLR and PLS with quadratic terms gave the same equation and the best predictive performance. The value of the squared cross-validated correlation coefficient (q(2)) was 0.682. In conclusion, the MLR method using animal clearance data from only two species and using easily calculated structural parameters can generally predict human clearance better than allometric methods. This approach can be applied to drugs with various characteristics.

Pharmacokinetics of ceftriaxone administered by the intravenous, intramuscular or subcutaneous routes to dogs

The purpose of this study was to investigate the pharmacokinetics of ceftriaxone after single intravenous (i.v.), intramuscular (i.m.) and subcutaneous (s.c.) doses in healthy dogs. Six mongrel dogs received ceftriaxone (50 mg/kg) by each route in a three-way crossover design. Blood samples were collected in predetermined times after drug administration. Results are reported as mean +/- standard deviation (SD). Total body clearance (Cl(t)) and apparent volume of distribution (V(z)) for the i.v. route were 3.61 +/- 0.78 and 0.217 +/- 0.03 mL/kg, respectively. Terminal half-life harmonic mean (t(1/2 lambda)) was 0.88; 1.17 and 01.73 h for the i.v., i.m and s.c. routes, respectively. Mean peak serum concentration (C(max)) was 115.10 +/- 16.96 and 69.28 +/- 14.55 microg/mL for the i.m and s.c. routes, respectively. Time to reach C(max) (t(max)) was 0.54 +/- 0.24 and 1.29 +/- 00.64 h for the i.m and s.c. routes, respectively. Mean absorption time (MAT) was 1.02 +/- 0.64 and 2.23 +/- 00.73 h for the i.m and s.c. routes, respectively. Bioavailability was 102 +/- 27 and 106 +/- 14% for the i.m and s.c. routes, respectively. Statistically significant differences were determined in C(max), t(max), MAT and t(1/2 lambda) of s.c. administered ceftriaxone when compared with the i.v and i.m. routes. These findings suggest that once or twice s.c. or i.m. daily administered ceftriaxone should be adequate to treat most susceptible infections in dogs.

Pharmacokinetics of ceftazidime in dogs following subcutaneous administration and continuous infusion and the association with in vitro susceptibility of Pseudomonas aeruginosa

OBJECTIVE

To determine the pharmacokinetics of ceftazidime following subcutaneous administration and continuous IV infusion to healthy dogs and to determine the minimum inhibitory concentration (MIC) of ceftazidime for clinical isolates of Pseudomonas aeruginosa.

ANIMALS

10 healthy adult dogs.

PROCEDURE

MIC of ceftazidime for 101 clinical isolates of P aeruginosa was determined in vitro. Serum concentrations of ceftazidime were determined following subcutaneous administration of ceftazidime (30 mg/kg of body weight) to 5 dogs and continuous IV infusion of ceftazidime (loading dose, 4.4 mg/kg; infusion rate, 4.1 mg/kg/h) for 36 hours to 5 dogs.

RESULTS

The MIC of ceftazidime for P aeruginosa was < or = 8 microg/ml; all isolates were considered susceptible. Following SC administration of ceftazidime, mean beta disappearance half-life was 0.8 hours, and mean serum ceftazidime concentration exceeded the MIC for P aeruginosa for only 4.3 hours. Two dogs had gastrointestinal tract effects. Mean serum ceftazidime concentration exceeded 16 microg/ml during continuous IV infusion. None of the dogs developed adverse effects.

CONCLUSIONS AND CLINICAL RELEVANCE

Administration of ceftazidime subcutaneously (30 mg/kg, q 4 h) or as a constant IV infusion (loading dose, 4.4 mg/kg; rate, 4.1 mg/kg/h) would maintain serum ceftazidime concentrations above the MIC determined for 101 clinical isolates of P aeruginosa. Use of these dosages may be appropriate for treatment of dogs with infections caused by P aeruginosa.

Antibacterial drug therapy. Focus on new drugs

This article will focus on the drugs for which there has been a recent or renewed interest in veterinary medicine. Some of these are new drugs that were recently introduced. Others discussed may be human-label drugs for which there has been recent interest in veterinary medicine because of the need for a more active drug or convenient regimen. For drugs such as the aminoglycosides included here, recent information has provided us with updated dosage guidelines.

The pharmacokinetics of ceftazidime in lactating and non-lactating cows

The pharmacokinetics of ceftazidime (CAZ) were studied in lactating (LTG) and non-lactating (NLTG) cows. Two groups (LTG and NLTG) of 5 healthy dairy cows were given ceftazidime (10 mg/ kg body weight) intravenously (i.v.) and intramuscularly (i.m.). Serum and milk (LTG) and serum samples (NLTG) were collected over a 24-h period post-administration. CAZ concentrations in serum and milk were determined by high-performance liquid chromatography, and an interactive and weighted-non-linear least-squares regression analysis was used to perform the pharmacokinetic analysis. The pharmacokinetic profiles in LTG and NLTG cows which had received CAZ i.v. fitted a three-compartment model and a two-compartment model, respectively. The CAZ concentration-time curves in serum and the area under the curve were greater and more sustained (p < 0.05) in the LTG cows by both routes, while the serum clearance (Cls = 72.5 +/- 18.1 ml/h per kg) was lower (p < 0.05) than that in the NLTG cows (Cls = 185.9 +/- 44.2 ml/h per kg). CAZ given i.v. exhibited a relatively long half-life of elimination (t1/2 beta (LTG) = 1.1 +/- 0.2 h; t1/2 beta (NLTG) = 1.4 +/- 0.3 h). Compared with other cephalosporins, CAZ had good penetration into the mammary gland (47.7 +/- 38.2% for CAZ i.v.; 51.1 +/- 39.0% for CAZ i.m.). Finally, the bioavailability of CAZ (F(LTG) = 98.9 +/- 36.8%; F(NLTG) = 77.1 +/- 25.3%) was suitable for its used by the i.m. route in lactating and non-lactating cows.

Pharmacokinetics of the novel cephalosporin cefepime (BMY-28142) in rats and monkeys

The disposition of the novel cephalosporin cefepime (BMY-28142) was characterized for intravenous administration of single doses to rats and cynomolgus monkeys, the species used most extensively for safety evaluation of the compound. Serial blood samples were collected from individual animals, and plasma was analyzed for intact cefepime by a high-pressure liquid chromatography-UV method. Assay results were evaluated by compartmental and noncompartmental methods to characterize pharmacokinetics for each species and dosage regimen. For intravenous (i.v.) bolus administration of 28 to 386 mg/kg (body weight) to rats, total body clearance (CL; 11.0 ml/min per kg) was essentially invariant with the dose; however, the terminal half-life (t1/2) and the steady-state distribution volume (Vss) increased with increasing dose level. After administration of 87 to 1,502 mg/kg by i.v. infusion, CL (12.5 ml/min per kg) was again similar for all dose groups. Mean t1/2 values (1.3 to 4.6 h) appeared unusually long for a cephalosporin in rats, and inordinately variable. No consistent differences among dose group mean Vss values were found. The maximal concentration of drug in plasma at the end of infusion was not a linear function of dose. For the cynomolgus monkey, kinetic parameters for 5-min i.v. infusions were linearly related to dose over the range of 10 to 600 mg/kg. Mean parameter values were t1/2 = 1.7 h, CL = 1.6 ml/min per kg, and Vss = 0.21 liters/kg. The pharmacokinetic results indicate substantive differences between the two species with respect to their response to toxicologic doses of cefepime.

In vitro studies on the antibacterial activities of YM-13115, a new broad-spectrum cephalosporin

The in vitro antibacterial activities of YM-13115, a new parenteral cephalosporin, were compared with those of ceftazidime, cefoperazone, and cefsulodin. The compound was highly active against the common members of the Enterobacteriaceae and 2 to 256 times more active than cefoperazone. YM-13115 was as active as ceftazidime against Citrobacter freundii, Proteus vulgaris, and Morganella morganii and two to four times more active than ceftazidime against Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Enterobacter aerogenes, Serratia marcescens, Proteus mirabilis, Providencia rettgeri, and Providencia stuartii. The activity of YM-13115 against Pseudomonas aeruginosa (with MICs of 0.78 and 3.13 micrograms/ml for 50 and 90% of the isolates, respectively) was ca. 2 times that of ceftazidime, 4 times that of cefsulodin, and 16 times that of cefoperazone. Against Haemophilus influenzae YM-13115 was more active than ceftazidime. YM-13115 was less active than ceftazidime, cefoperazone, and cefsulodin against Staphylococcus aureus and Staphylococcus epidermidis. The concentrations of YM-13115 required to inhibit the growth of 90% of the isolates of Streptococcus pyogenes and Streptococcus pneumoniae were 0.78 and 1.56 microgram/ml, respectively, but concentrations above 100 micrograms/ml were required to inhibit Streptococcus faecalis. YM-13115 was not hydrolyzed by the common plasmid and chromosomal beta-lactamases. YM-13115 is extremely active against P. aeruginosa and members of the Enterobacteriaceae.