Plasma clearance

A study on catalytic and non-catalytic sites of H5N1 and H1N1 neuraminidase as the target for chalcone inhibitors

The H1N1 pandemic in 2009 and the H5N1 outbreak in 2005 have shocked the world as millions of people were infected and hundreds of thousands died due to the infections by the influenza virus. Oseltamivir, the most common drug to block the viral life cycle by inhibiting neuraminidase (NA) enzyme, has been less effective in some resistant cases due to the virus mutation. Presently, the binding of 10 chalcone derivatives towards H5N1 and H1N1 NAs in the non-catalytic and catalytic sites was studied using molecular docking. The in silico study was also conducted for its drug-like likeness such as Lipinski Rule, mutagenicity, toxicity and pharmacokinetic profiles. The result demonstrates that two chalcones (1c and 2b) have the potential for future NA inhibitor development. Compound 1c inhibits H5N1 NA and H1N1 NA with IC₅₀ of 27.63 µM and 28.11 µM, respectively, whereas compound 2b inhibits NAs with IC₅₀ of 87.54 µM and 73.17 µM for H5N1 and H1N1, respectively. The in silico drug-like likeness prediction reveals that 1c is 62% better than 2b (58%) in meeting the criteria. The results suggested that 1c and 2b have potencies to be developed as non-competitive inhibitors of neuraminidase for the future development of anti-influenza drugs.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1186/s13765-021-00639-w.

Tylosin Dosage Adjustment Based on Allometric Scaling in Male Turkeys

Turkeys' body weight (BW) increases 10-fold within only 2.5 months, leading to a change in the pharmacokinetics (PK) of drugs according to allometric principles. Thus, the same dosage may lead to age-dependent variability in efficacy, in particular, to treatment failure and/or selection for resistance. The study aimed to investigate whether a non-linear dosage based on a published allometric model for tylosin clearance, may optimize the internal exposure in growing turkeys. The single dose PK study was performed on turkeys aged 6, 9.5, 13 and 17 weeks (BW from 1.75 kg to 15.75 kg). Tylosin was administered intravenously (i.v.) or orally (p.o.) according to following protocols: Dose = 31.6 × BW0.58 or Dose = 158 × BW0.58, respectively. Plasma tylosin was measured using high-performance liquid chromatography and non-compartmental PK analysis was performed. The area under the curve (AUClast) after i.v. administration was 8.90 ± 1.01; 7.51 ± 1.11; 6.54 ± 1.20 and 8.01 ± 1.75 mg × h/L in 6-; 9.5-; 13- and 17-week-old turkeys, respectively. After p.o. administration AUClast was 4.80 ± 2.92; 4.60 ± 2.45; 3.00 ± 1.49 and 3.24 ± 2.00 mg × h/L in respective age groups indicating high variability. For i.v. administration, the non-linear dosage allowed to minimize the age-dependent variability in AUC. However, due to low oral bioavailability (8-12%) and resulting interindividual variability, the proposed approach may not improve tylosin efficacy in turkeys under farm conditions.

Pharmacokinetics of tulathromycin in pregnant ewes (Ovis aries) challenged with Campylobacter jejuni

The purpose of this study was to evaluate the pharmacokinetics of tulathromycin in the plasma and maternal and fetal tissues of pregnant ewes when administered within 24 hours of a single, IV Campylobacter jejuni (C. jejuni) challenge. Twelve, pregnant ewes between 72-92 days of gestation were challenged IV with C. jejuni IA3902 and then treated with 1.1 ml/45.36 kg of tulathromycin subcutaneously 18 hours post-challenge. Ewes were bled at predetermined time points and euthanized either at a predetermined time point or following the observation of vaginal bleeding or abortion. Following euthanasia, tissues were collected for bacterial culture, pharmacokinetics and histologic examination. The maximum (geometric) mean tulathromycin plasma concentration was estimated at 0.302 μg/mL, with a peak level observed at around 1.2 hours. The apparent systemic clearance of tulathromycin was estimated at 16.6 L/h (or 0.28 L/kg/h) with an elimination half-life estimated at approximately 22 hours. The mean tissue concentrations were highest in the uterus (2.464 μg/g) and placentome (0.484 μg/g), and were lowest in fetal liver (0.11 μg/g) and fetal lung (0.03 μg/g). Compared to previous reports, results of this study demonstrate that prior IV administration of C. jejuni appeared to substantially alter the pharmacokinetics of tulathromycin, reducing both the peak plasma concentrations and elimination half-life. However, additional controlled trials are required to confirm those observations.

Pharmacokinetics of furosemide in goats following intravenous, intramuscular, and subcutaneous administrations

Furosemide, a loop diuretic drug, is recommended for use in cases of edema, ascites, congestive heart failure, toxicosis, and acute renal failure in goats. However, its pharmacokinetics and bioavailability have not been reported yet in this species. The aim of this study was to determine the pharmacokinetics and bioavailability of furosemide in goats following intravenous (IV), intramuscular (IM), and subcutaneous (SC) administrations at a dose of 2.5 mg/kg. Six clinically healthy goats received furosemide by each route in a three-way crossover pharmacokinetic design with a 15-day washout period between administrations. The plasma concentrations of furosemide were determined using the high-performance liquid chromatography-UV method and analyzed by non-compartmental analysis. The elimination half-life following IV, IM, and SC administration was 0.71 (0.67-0.76) h, 0.69 (0.61-0.74) h, and 0.70 (0.67-0.79) h, respectively. The volume of distribution at steady state and total clearance for the IV route were 0.17 (0.16-0.19) L/kg and 0.30 (0.27-0.33) L/h/kg, respectively. The peak plasma concentrations of furosemide following IM and SC administrations were 11.19 (10.33-11.95) and 6.49 (5.92-7.00) μg/ml at 0.23 (0.16-0.25) and 0.39 (0.33-0.42) h, respectively. The bioavailability was 109.84 (104.92-116.99)% and 70.80 (55.77-86.67)% for the IM and SC routes, respectively. The pharmacokinetics of furosemide following the IV, IM, and SC administrations in goats demonstrated significant differences, which may have clinical and toxicological implications requiring further investigations.

Novel, selective acrylamide linked quinazolines for the treatment of double mutant EGFR-L858R/T790M Non-Small-Cell lung cancer (NSCLC)

T790M mutation is the most common mechanism of acquired resistance to first-generation epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs). To overcome this resistance, 4-anilinoquinazoline-based irreversible inhibitors afatinib, dacomitinib has been developed. However, the clinical application of these irreversible inhibitors is limited due to its narrow selectivity against L858R/T790M mutant EGFR. In an attempt to develop potent and selective EGFR T790M inhibitors, we have designed and synthesized two series of novel acrylamide linked quinazolines. Among them, compounds 2i (IC₅₀ 0.171 µM) and 11h (IC₅₀ 0.159 µM) were identified as potent compounds, which displayed selective and potent anti-proliferative activity on gefitinib-resistant cell line NCI-H1975 as compared to the gefitinib and WZ4002 in cellular assay. Furthermore, a molecular dynamic simulation of 11h was carried out to assess the stability to form a complex with the L858R/T790M EGFR Kinase domain, which demonstrated that complex was stable for the 100 ns and form strong crucial covalent binding contacts with the thiol group of Cys797 residue. Finally, satisfactory in silico pharmacokinetics properties of 2i, 11h and 11i compounds were predicted. The synthesized compounds were also evaluated for in vitro cytotoxic activity/hepatotoxicity against HepG2 cell line through MTT assay. The results revealed that compounds exhibited lower cytotoxicity to HepG2 cells.

Doxycycline pharmacokinetics in geese

The study aims to describe the pharmacokinetics of doxycycline after a single intravenous and oral dose (20 mg/kg) in geese. In addition, two multiple‐dose simulations have been performed to investigate the predicted plasma concentration after either a 10 or 20 mg/kg daily administration repeated consecutively for 5 days. Ten geese were enrolled in a two‐phase cross‐over study with a washout period of two weeks. All animals were treated intravenously and orally with doxycycline, and blood samples were collected up to 48 h after drug administration. Sample analysis was performed using a validated HPLC‐UV method. A non‐compartmental approach was used to evaluate the pharmacokinetic parameters of the drug. A long elimination half‐life was observed (13 h). The area under the curve was statistically different between the two treatments, with the oral bioavailability being moderate (43%). The pharmacokinetic/pharmacodynamic index (%T>MIC) during the 48 h treatment period in the present study (71%) suggests that doxycycline appears to have therapeutic efficacy against some Mycoplasma species in the goose. The multiple‐dose simulations showed a low accumulation index. A dosage of 10 mg/kg/day for 5 days seemed to be adequate for a good therapeutic efficacy without reaching unnecessarily high plasma concentrations.

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 and Bioavailability of Carprofen in Rainbow Trout (Oncorhynchus mykiss) Broodstock

The aim of this study was to determine the pharmacokinetics of carprofen following intravenous (IV), intramuscular (IM) and oral routes to rainbow trout (Oncorhynchus mykiss) broodstock at temperatures of 10 ± 1.5 °C. In this study, thirty-six healthy rainbow trout broodstock (body weight, 1.45 ± 0.30 kg) were used. The plasma concentrations of carprofen were determined using high-performance liquid chromatography and pharmacokinetic parameters were calculated using non-compartmental analysis. Carprofen was measured up to 192 h for IV route and 240 h for IM, and oral routes in plasma. The elimination half-life (t1/2λz) was 30.66, 46.11, and 41.08 h for IV, IM and oral routes, respectively. Carprofen for the IV route showed the total clearance of 0.02 L/h/kg and volume of distribution at steady state of 0.60 L/kg. For IM and oral routes, the peak plasma concentration (Cmax) was 3.96 and 2.52 μg/mL with the time to reach Cmax of 2 and 4 h, respectively. The bioavailability was 121.89% for IM route and 78.66% for oral route. The favorable pharmacokinetic properties such as the good bioavailability and long t1/2λz for IM and oral route of carprofen suggest the possibility of its effective use for the treatment of various conditions in broodstock.

Worse capecitabine treatment outcome in patients with a low skeletal muscle mass is not explained by altered pharmacokinetics

Background

A low skeletal muscle mass (SMM) has been associated with increased toxicity and shorter survival in cancer patients treated with capecitabine, an oral prodrug of 5‐fluorouracil (5‐FU). Capecitabine and its metabolites are highly water‐soluble and, therefore, more likely to distribute to lean tissues. The pharmacokinetics (PK) in patients with a low SMM could be changed, for example, by reaching higher maximum plasma concentrations. In this study, we aimed to examine whether the association between a low SMM and increased toxicity and shorter survival could be explained by altered PK of capecitabine and its metabolites.

Methods

Previously, a population PK model of capecitabine and metabolites in patients with solid tumors was developed. In our analysis, we included patients from this previous analysis for which evaluable abdominal computed tomography (CT)‐scans were available. SMM was measured on CT‐scans, by single slice evaluation at the third lumbar vertebra, using the Slice‐o‐Matic software. The previously developed population PK model was extended with SMM as a covariate, to assess the association between SMM and capecitabine and metabolite PK.

Results

PK and SMM data were available from 151 cancer patients with solid tumors. From the included patients, 55% had a low SMM. No relevant relationships were found between SMM and the PK parameters of capecitabine and, the active and toxic metabolite, 5‐FU. SMM only correlated with the PK of the, most hydrophilic, but inactive and non‐toxic, metabolite α‐fluoro‐β‐alanine (FBAL). Patients with a low SMM had a smaller apparent volume of distribution and lower apparent clearance of FBAL.

Conclusions

No alterations in PK of capecitabine and the active and toxic metabolite 5‐FU were observed in patients with a low SMM. Therefore, the previously identified increased toxicity and shorter survival in patients with a low SMM, could not be explained by changes in pharmacokinetic characteristics of capecitabine and metabolites.

Interaction between apigenin and sodium deoxycholate with raloxifene: A potential risk for clinical practice

Apigenin (API) and sodium deoxycholate (NaDC) have different pharmacodynamic properties and can affect pharmacokinetics of drugs without causing significant toxicity. The aim of our study was to investigate the effect of API and NaDC on raloxifene pharmacokinetics in rats as well as on hemostasis parameters after applying the raloxifene therapeutic dose. Rats were treated daily with oral single dose of saline solution (1 ml/kg), API (10 mg/kg) and/or NaDC (4 mg/kg) for 7 days. Raloxifene was given orally or intravenously in a single dose (6 mg/kg) and during period of 24 h blood samples, feces and urine samples were collected. Blood samples were collected at the 15th, 30th, 45th, 60th, 90th minute and 2, 3, 4, 6, 8, 10, 12 and 24 h after raloxifene administration. Urine and feces samples were collected in the 3th, 6^h, 12th and 24th hour of the experiment. Rats were divided into 10 groups each of which contained 6 animals. Differences were considered statistically significant if p<0.05. Pretreatment with NaDC and API affected raloxifene pharmacokinetic profile after intravenous application. NaDC lead to statistically significant decrease in raloxifene serum concentration and increased volume of distribution and clearance as well as halftime of elimination, while API has also decreased also raloxifene serum concentrations and increased volume of distribution but not as profoundly as NaDC alone. Difference was also noticed in clearance where it was significantly increased in group pretreated with NaDC and slightly decreased in group pretreated with API. NaDC and API increased raloxifene amount in feces, both after peroral (p<0.05) and intravenous application. However, peroral application of raloxifene did not produce measurable raloxifene serum concentration in neither of investigated groups. NaDC shortened activated partial thromboplastin time (aPTT) and prothrombin time (PT). API reduced aPTT, PT and d-dimer level. Fibrinogen level was significantly increased in all experimental groups. Both NaDC and apigenin had significant influence on raloxifene pharmacokinetics and can potentiate the raloxifene effects on hemostasis parameters, by increasing its bioavailability. These substances may be the subject of further investigation into the formulation of raloxifene and other medicines as depot preparations, which could prolong the dosing interval and thus improve patient compliance and quality of life.

Grapiprant: A snapshot of the current knowledge

Grapiprant is the pioneer member of the novel piprant class, a potent and specific antagonist of the prostaglandin E2 receptor 4. It has been approved in veterinary medicine for the control of pain and inflammation associated with osteoarthritis in dogs at the dose regimen of 2 mg/kg once a day by the FDA and EMA (for pain only) in 2016 and 2018, respectively. The aim of this narrative review was to report the analytical methods, pharmacokinetics, pharmacodynamics and safety of grapiprant in several animal species using the best available published scientific evidence. In conclusion, most of the analytical methods proposed for grapiprant detection are simple, reliable, sensitive and validated. The pharmacokinetics show discrepancies between animal species. The therapeutic efficacy seems more suited to chronic rather than acute pain.

Influence of general anaesthesia on the intravenous acetaminophen pharmacokinetics in Beagle dogs

OBJECTIVE

To determine if general anaesthesia influences the intravenous (IV) pharmacokinetics (PK) of acetaminophen in dogs.

STUDY DESIGN

Prospective, crossover, randomized experimental study.

ANIMALS

A group of nine healthy Beagle dogs.

METHODS

Acetaminophen PK were determined in conscious and anaesthetized dogs on two separate occasions. Blood samples were collected before, and at 5, 10, 15, 30, 45, 60 and 90 minutes and 2, 3, 4, 6, 8, 12 and 24 hours after 20 mg kg^-1 IV acetaminophen administration. Haematocrit, total proteins, albumin, alanine aminotransferase, aspartate aminotransferase, urea and creatinine were determined at baseline and 24 hours after acetaminophen. The anaesthetized group underwent general anaesthesia (90 minutes) for dental cleaning. After the administration of dexmedetomidine (3 μg kg^-1) intramuscularly, anaesthesia was induced with propofol (2-3 mg kg^-1) IV, followed by acetaminophen administration. Anaesthesia was maintained with isoflurane in 50% oxygen (Fe'Iso 1.3-1.5%). Dogs were mechanically ventilated. Plasma concentrations were analysed with high-performance liquid chromatography. PK analysis was undertaken using compartmental modelling. A Wilcoxon test was used to compare PK data between groups, and clinical laboratory values between groups, and before versus 24 hours after acetaminophen administration. Data are presented as median and range (p < 0.05).

RESULTS

A two-compartmental model best described time-concentration profiles of acetaminophen. No significant differences were found for volume of distribution values 1.41 (0.94-3.65) and 1.72 (0.89-2.60) L kg^-1, clearance values 1.52 (0.71-2.30) and 1.60 (0.91-1.78) L kg^-1 hour^-1 or terminal elimination half-life values 2.45 (1.45-8.71) and 3.57 (1.96-6.35) hours between conscious and anaesthetized dogs, respectively. Clinical laboratory variables were within normal range. No adverse effects were recorded.

CONCLUSIONS AND CLINICAL RELEVANCE

IV acetaminophen PK in healthy Beagle dogs were unaffected by general anaesthesia under the study conditions. Further studies are necessary to evaluate the PK in different clinical contexts.

Determination of the route of excretion of robenacoxib (Onsior™) in cats and dogs: A pilot study

The objective of the studies was to determine the route of excretion, faecal or urinary, of the nonsteroidal anti-inflammatory drug (NSAID) robenacoxib (Onsior™) in cats and dogs. The studies employed a two-part crossover design in 4 beagle dogs (2 female and 2 male, age 36-41 months and body weight 9.0-10.3 kg) and a parallel group comparison of two groups each of 3 domestic short-hair cats (2 female and 4 castrated male, age 35-73 months and body weight 3.0-5.7 kg). Animals were administered single doses of 1 (dog) or 2 (cat) mg/kg of [¹⁴ C]-robenacoxib by intravenous (IV) and oral routes. Venous blood samples were taken and analysed for robenacoxib concentration. Faeces and urine were collected for 4 (cats) or 7 (dogs) days and analysed for radioactivity. Robenacoxib was eliminated rapidly from blood (≤ 8 hr). In dogs, expressed as the percentage of the administered dose and adjusted so that faecal plus urine recovery was 100%, the mean (SD) excretion in faeces and urine was, respectively, 64.6% (4.30) and 35.4% (4.3) after IV and 66.7% (6.9) and 33.3% (6.9) after oral administration. The respective values in cats, in faeces and urine, were 72.5% (4.6) and 27.5% (4.6) after IV and 78.5% (2.6) and 21.5% (2.6) after oral administration. In conclusion, excretion of systemically available robenacoxib in cats and dogs was mixed via both faeces and urine, but predominately faecal (~64.6% in dogs and ~72.5% in cats) and assumed to be via biliary excretion.

Cell-specific drug targeting in the lung

Non-targeted drug delivery systems have several limitations including the decreased bioavailability of the drug, poor stability and rapid clearance in addition to off-target distribution. Cell-specific targeted delivery approaches promise to overcome some of these limitations and enhance therapeutic selectivity. In this review, we aim to discuss cell-specific targeted approachesin the lung at the biochemical and molecular levels. These approaches include;a) directly administered small molecule drugs with intracellular action; b) targeted biologics and synthetic hybrids with extracellular action; c) site activateddrugs; and d) delivery systems.We discuss the pharmaceutical and biochemical parameters that govern the fate of drug molecules at delivery sites while presenting an overview of relevant literature surrounding this area of research and current advancements.

Pharmacokinetics of meloxicam, carprofen, and tolfenamic acid after intramuscular and oral administration in Japanese quails (Coturnix coturnix japonica)

The aim of this study was to determine the pharmacokinetics of meloxicam (MLX), carprofen (CRP), and tolfenamic acid (TA) in Japanese quails (Coturnix coturnix japonica) following intramuscular (IM) and oral administration at doses of 1, 10, and 2 mg/kg, respectively. A total of 72 quails were randomly divided into 3 equal groups as MLX, CRP, and TA. Each group was separated into two sub-groups that received IM and oral administration of each drug. Plasma concentrations of MLX, CRP, and TA were determined using HPLC-UV and analyzed by non-compartmental method. The t_1/2ʎz and MRT of MLX, CRP, and TA after oral administration were similar to those after IM administration. The V_darea /F of MLX, CRP, and TA after IM administration was 0.28, 2.05, and 0.20 L/kg. The Cl/F of MLX, CRP, and TA after IM administration was 0.12, 0.19, and 0.09 L/h/kg. MLX, CRP, and TA after oral administration showed significantly lower C_max and longer T_max compared with IM administration. The relative bioavailability of MLX, CRP, and TA following oral administration in quails was 76.13%, 61.46%, and 57.32%, respectively. The IM and oral route of MLX, CRP, and TA can be used for the treatment of various conditions in quails. However, further research is necessary to determine the pharmacodynamics and safety of MLX, CRP, and TA before use in quails.

Topical ophthalmic atropine in horses, pharmacokinetics and effect on intestinal motility

BACKGROUND

Topical ophthalmic atropine sulfate is an important part of the treatment protocol in equine uveitis. Frequent administration of topical atropine may cause decreased intestinal motility and colic in horses due to systemic exposure. Atropine pharmacokinetics are unknown in horses and this knowledge gap could impede the use of atropine because of the presumed risk of unwanted effects. Additional information could therefore increase safety in atropine treatment.

RESULTS

Atropine sulfate (1 mg) was administered in two experiments: In part I, atropine sulfate was administered intravenously and topically (manually as eye drops and through a subpalpebral lavage system) to six horses to document atropine disposition. Blood-samples were collected regularly and plasma was analyzed for atropine using UHPLC-MS/MS. Atropine plasma concentration was below lower limit of quantification (0.05 μg/L) within five hours, after both topical and IV administration. Atropine data were analyzed by means of population compartmental modeling and pharmacokinetic parameters estimated. The typical value was 1.7 L/kg for the steady-state volume of distribution. Total plasma clearance was 1.9 L/h‧kg. The bioavailability after administration of an ophthalmic preparation as an eye drop or topical infusion were 69 and 68%, respectively. The terminal half-life was short (0.8 h). In part II, topical ophthalmic atropine sulfate and control treatment was administered to four horses in two dosing regimens to assess the effect on gastro-intestinal motility. Borborygmi-frequency monitored by auscultation was used for estimation of gut motility. A statistically significant decrease in intestinal motility was observed after administration of 1 mg topical ophthalmic atropine sulfate every three hours compared to control, but not after administration every six hours. Clinical signs of colic were not observed under any of the treatment protocols.

CONCLUSIONS

Taking the plasma exposure after topical administration into consideration, data and simulations indicate that eye drops administrated at a one and three hour interval will lead to atropine accumulation in plasma over 24 h but that a six hour interval allows total washout of atropine between two topical administrations. If constant corneal and conjunctival atropine exposure is required, a topical constant rate infusion at 5 μg/kg/24 h offers a safe alternative.

Methotrexate Triglutamate as a Determinant of Clinical Response in Mexican Patients With Rheumatoid Arthritis: Pharmacokinetics and Dose Recommendation

Methotrexate is the gold standard treatment in rheumatoid arthritis. Once absorbed, it is internalized in cells, where glutamate residues are added to produce polyglutamated forms, which are responsible for the effect of methotrexate. The aim of the current study is to determine the relationship between methotrexate triglutamate concentrations and the clinical evolution in rheumatoid arthritis patients, as well as to characterize the variability in both features to propose strategies for low-dose methotrexate optimization. The quantification of methotrexate triglutamate concentration in red blood cells was performed through ultra-performance liquid chromatography coupled with mass spectrometry. Polymorphisms of genes involved in the formation of polyglutamates were determined by real-time polymerase chain reaction. A multivariate regression was performed to determine the covariates involved in the variability of methotrexate triglutamate concentrations and a population pharmacokinetics model was developed through nonlinear mixed-effects modeling. Disease activity score changed according to methotrexate triglutamate concentrations; patients with good response to treatment had higher concentrations than moderate or nonresponding patients. The methotrexate triglutamate concentrations were related to time under treatment, dose, red blood cells, and body mass index. A 1-compartment open model was selected to estimate the pharmacokinetic parameters; the typical total clearance (L/day) was determined as 1.45 * (body mass index/28 kg/m² ) * (red blood cells/4.6 × 10⁶ cells/μL) and the volume of distribution was 52.4 L, with an absorption rate of 0.0346/day and a fraction metabolized of 1.03%. Through the application of the model, the initial dose of methotrexate is proposed on the basis of stochastic simulations and considering methotrexate triglutamate concentrations found in responders patients.

Extracorporeal Therapies in the Emergency Room and Intensive Care Unit

Extracorporeal treatments create opportunity for removing disease causing solutes within blood. Intoxications, renal failure, and immune-mediated diseases may be managed with these treatments, often providing new hope for patients with severe or refractory disease. Understanding solute pharmacokinetics and the limitations of each type of extracorporeal technique can allow for the selection of the optimal treatment modality.

Evaluating a tylosin dosage regimen for treatment of Staphylococcus delphini infection in mink (Neovison vison): a pharmacokinetic-pharmacodynamic approach

Staphylococcus delphini is one of the most common pathogens isolated from mink infections, especially dermatitis. Tylosin (TYL) is used frequently against these infections, although no evidence-based treatment regimen exists. This study aimed to explore the dosage of TYL for infections caused by S. delphini in mink. Two animal experiments with a total of 12 minks were conducted to study the serum pharmacokinetic (PK) characteristics of TYL in mink after 10 mg/kg IV and oral dosing, respectively. The concentration of TYL in serum samples collected before and eight times during 24 h after TYL administration was quantitated with liquid chromatography quadrupole time-of-flight mass spectrometry, and the TYL disposition was analyzed using non-linear mixed effect analysis. The pharmacodynamics (PD) of TYL against S. delphini were studied using semi-mechanistic modeling of in vitro time-kill experiments. PKPD modeling and simulation were done to establish the PKPD index and dosage regimen. The disposition of TYL was described by a two-compartmental model. The area under the free concentration-time curve of TYL over the minimum inhibitory concentration of S. delphini (fAUC/MIC) was determined as PKPD index with breakpoints of 48.9 and 98.7 h for bacteriostatic and bactericidal effect, respectively. The calculated daily oral dose of TYL was 2378 mg/kg, which is 238-fold higher than the currently used TYL oral dosage regimen in mink (10 mg/kg). Accordingly, sufficient TYL concentrations are impossible to achieve in mink plasma, and use of this drug for extra-intestinal infections in this animal species must be discouraged.

Pharmacokinetics of tolfenamic acid after different administration routes in geese (Anser cygnoides)

The pharmacokinetics and bioavailability of tolfenamic acid were determined in geese (Anser cygnoides) following intravenous (IV), intramuscular (IM), subcutaneous (SC), and oral administrations at 2 mg/kg dose. In this study, eight healthy geese (3.5 ± 0.5 kg) were used. The study was performed in four periods according to a crossover design with a 15-day washout period between two administrations. The plasma concentrations of tolfenamic acid were analyzed using HPLC-UV, and pharmacokinetic parameters were calculated by noncompartmental analysis. The elimination half-life was 1.73, 2.51, 2.34, and 2.31 hr for IV, IM, SC, and oral routes, respectively. The volume of distribution at steady state and total clearance after IV administration were 0.25 L/kg and 0.16 L hr^-1  kg^-1 , respectively. The peak plasma concentrations of tolfenamic acid after IM, SC, and oral administrations were 4.89, 2.94, and 2.92 μg/ml at 0.25, 0.75, and 1 hr, respectively. The bioavailability was 87.91, 77.87, and 76.03% for the IM, SC, and oral routes, respectively. Tolfenamic acid, which exhibits the good bioavailability and plasma concentration following IM, SC, and oral administrations at 2 mg/kg dose, may be useful in the treatment of inflammatory disease conditions in geese.

Pharmacokinetics of tolfenamic acid in goats after different administration routes

The aim of this study was to determine the pharmacokinetics and bioavailability of tolfenamic acid in goats after intravenous (IV), intramuscular (IM), subcutaneous (SC), and oral (PO) administrations at 2 mg/kg dose. In this study, eight clinically healthy goats were used. The study comprised four periods, according to a crossover design with at least a 15-day washout period between treatments. Plasma concentrations of tolfenamic acid were determined by HPLC-UV, and the pharmacokinetic parameters were estimated using a non-compartmental method. Following IV administration, terminal elimination half-life, volume of distribution at steady state, and total clearance were 1.60 h, 0.37 L/kg, and 0.27 L/h/kg, respectively. The mean peak plasma concentration following IM, SC, and PO administrations was 1.77, 1.22, and 0.30 μg/ml, respectively. The mean bioavailability following IM, SC, and PO administrations was 64.46, 55.43, and 19.46%, respectively. The PO route, which exhibits both the low plasma concentration and bioavailability, is not recommended in goats. The IV, IM, and SC routes, which show comparable pharmacokinetic profiles, may be proposed for use in goats. However, the multi-dose and pharmacodynamic studies are necessary to establish more accurately its safety and efficacy in the goat.

Allometric Optimization of Enrofloxacin Dosage in Growing Male Turkeys: Empirical Evidence for Improved Internal Exposure

Rapid weight gain in turkeys causes a major change in the pharmacokinetics of drugs, leading to age-dependent variability in the internal exposure and, possibly, treatment failure and/or selection for antimicrobial resistance in young individuals. The aim of the study was to investigate whether a non-linear dosing protocol that accounts for the previously established allometric relation between enrofloxacin clearance and body weight (BW) may optimize the internal exposure to enrofloxacin in growing male turkeys. Enrofloxacin was administered four times, between the age of 5 and 16.5 weeks, when the turkeys’ BW increased from 1.47 to 14.92 kg. Enrofloxacin was given intravenously (i.v.) or orally at the dose calculated as follows: Dose = 30 × BW^0.59. After i.v. administration, the internal exposure to the drug—quantified as the area under the concentration–time curve (AUC)—was showing little age-related variation. The coefficient of variation (CV) for AUC in all individuals (15.7%) was only slightly higher than within the age groups (5.4–13.7%). After oral drug administration, CV for AUC in all individuals (22.1%) was similar as within the age groups (8.7–32.2%). These results show that intra-species allometric scaling may be efficiently implemented in the non-linear approach to enrofloxacin dosage in turkeys in order to obtain a precise internal exposure for the optimal antimicrobial effect.

Determination of the pharmacokinetic-pharmacodynamic cut-off values of marbofloxacin in horses to support the establishment of a clinical breakpoint for antimicrobial susceptibility testing

BACKGROUND

Marbofloxacin (MBX), a fluoroquinolone (FQ), is considered as a critical antibiotic requiring antimicrobial susceptibility testing (AST) for prudent use. No clinical breakpoint (CBP) currently exists to interpret the results of such tests in horses.

OBJECTIVES

To compute PK/PD cut-offs (PK/PD_CO ) that is one of the three minimum inhibitory concentrations (MICs) considered establishing a CBP for antimicrobial susceptibility test interpretation.

STUDY DESIGN

A meta-analysis conducted by combining five sets of previously published pharmacokinetic data, obtained in clinical and nonclinical settings.

METHODS

Horses (n = 131) received MBX intravenously at doses of either 2 or 10 mg/kg BW. They were richly sampled (five or six samples per horse). A population model was built to generate a virtual population of 5000 MBX disposition curves by Monte Carlo simulations (MCS) over 24 hours. The selected PK/PD index was the ratio of Area Under the free plasma concentration-time Curve divided by the MIC (fAUC/MIC). The PK/PD_CO , which is the highest MIC for which 90% of horses can achieve an a priori selected critical value for the numerical value of the PK/PD index, was established for Gram-positive and Gram-negative bacteria for a dose of 2 mg/kg.

RESULTS

The PK/PD_CO of MBX in horses was 0.125 mg/L for Gram-positive pathogens and 0.0625 mg/L for Gram-negative pathogens. MBX MICs determined by broth microdilution for 54 Escherichia coli and 189 Streptococcus equi isolates are reported.

MAIN LIMITATION

No clinical data are taken into account in the determination of a PK/PD_co .

CONCLUSION

The computed PK/PD_co predicts that MBX may be efficacious in horses to treat infections associated with Enterobacteriaceae but unlikely to those involving Staphylococcus aureus or Streptococcus equi.

Pharmacokinetics and Tissue Levels of Pantoprazole in Neonatal Calves After Intravenous Administration

Background: Neonatal calves are at risk of developing abomasal ulceration, but there is a lack of pharmacokinetic data for potential anti-ulcerative therapies, such as pantoprazole, in ruminant species. Objective: The study objectives were to estimate plasma pharmacokinetic parameters for pantoprazole in neonatal dairy calves after intravenous (IV) administration. A secondary objective was to quantify the concentrations of pantoprazole in edible tissues after IV dosing. Methods: Pantoprazole was administered to 9 neonatal Holstein calves at a dose of 1 mg/kg IV. Plasma samples were collected over 24 h and analyzed via HPLC-MS for determining pantoprazole concentrations. Pharmacokinetic parameters were derived via non-compartmental analysis. Tissue samples were collected at 1, 3, and 5 days after administration and analyzed via HPLC-MS. Results: Following IV administration, plasma clearance, elimination half-life, and volume of distribution of pantoprazole were estimated at 4.46 mL/kg/min, 2.81 h, and 0.301 L/kg, respectively. The global extraction ratio was estimated at 0.053 ± 0.015. No pantoprazole was detected in the edible tissues 1, 3, or 5 days after administration. A metabolite, pantoprazole sulfone was detected in all the edible tissues 1 and 3 days after administration. Conclusion: The reported plasma clearance for pantoprazole is less than that reported for alpacas but higher than reported in foals. The elimination half-life in calves appears to be longer than observed in foals and alpacas. While pantoprazole sulfone was detected in the tissues after IV administration, further research is needed as to the metabolism and potential tissue accumulation of other pantoprazole metabolites in calves. Future pharmacodynamic studies are necessary to determine the efficacy of pantoprazole on abomasal acid suppression in calves.

Perioperative pharmacokinetics and pharmacodynamics of meloxicam in emus (Dromaius novaehollandiae) of different age groups using nonlinear mixed effect modelling

Meloxicam is a widely used nonsteroidal anti-inflammatory drug in avian species. However, variability in pharmacokinetic (PK) and pharmacodynamic (PD) parameters in birds warrants species-specific studies for dose and dosing interval optimization. We performed a perioperative PK study of meloxicam (0.5 mg/kg, intravenously) on emus of three different age groups: 3 chicks (5 weeks old, 3.5 kg), 4 juveniles (26 weeks old, 18.8 kg) and 6 adults (66 weeks old, 38.8 kg). A two-compartment population PK model including weight as a significant covariate on clearance and central volume of distribution (V1) best fitted the data. The typical values (20 kg bird) for clearance and V1 were 0.54 L/kg/h and 0.095 L/kg. Both parameters significantly decreased with increasing weight/age. Meloxicam potency and selectivity for COX-1 and COX-2 were measured in whole blood assays (TxB₂ production endpoint). Meloxicam was partially selective in emus (IC₅₀ COX-1:COX-2 = 9.1:1). At the current empirical dose (0.5 mg/kg/24 hr), plasma meloxicam concentration is above IC₅₀ of COX-2 for only 2 hr. PK/PD predicted dose required for 80% COX-2 inhibition over 24 hr were 3.4, 1.4 and 0.95 L/kg/day in chicks, juveniles and adult emus, respectively. The safety, therapeutic efficacy and practicality of modifying the daily dose or dose interval should be considered for dose recommendations in emus.

Comparative Pharmacokinetics of Meloxicam Between Healthy Post-partum vs. Mid-lactation Dairy Cattle

Lactating dairy cattle are at risk for various painful conditions throughout their life, such as lameness, parturition, mastitis, and metabolic disorders. These conditions necessitate adequate methods of analgesia to address welfare concerns through efficacious pain mitigation. As no method of analgesia has been approved for lactating dairy cattle, to date, research is necessary to determine effective pain management strategies for dairy cattle. In both the European Union and Canada, meloxicam has been approved for use in lactating dairy cattle as a methodology for pain control. The objective of this study was to characterize the pharmacokinetics of meloxicam administered orally and intravenously to lactating dairy cattle in the post-partum vs. mid-lactation period. In this parallel study design, 12 healthy, lactating Holsteins were enrolled within 24 h of freshening and randomly allocated to intravenous (0.2 mg/kg) or oral (1.0 mg/kg) meloxicam administration treatment groups. They were matched based on parity to 12, healthy cows that were considered mid-lactation [>150 days-in-milk (DIM)] to receive the same treatment. Based on meloxicam formulation, sampling times varied and plasma was collection via jugular venipuncture for 6 days. Plasma drug concentrations were evaluated using liquid chromatography coupled with mass spectroscopy and pharmacokinetic properties were evaluated using non-compartmental (i.e., statistical moments) analysis. Results indicated a decreased systemic clearance of meloxicam in post-partum relative to mid-lactation cows, which resulted in a longer half-life and increased total exposure independent of mode of administration. These results suggest a need for dose adjustments based on stage in lactation and further assessment of the impact of days-in-milk on milk withholding period.

Pharmacokinetics of Intravenous, Intramuscular, Oral, and Transdermal Administration of Flunixin Meglumine in Pre-wean Piglets

Castration and tail-docking of pre-wean piglets are common procedures that are known to induce pain and would benefit from pain mitigation. Flunixin meglumine (FM) is a non-steroidal anti-inflammatory drug currently approved in the United States for pyrexia in swine and lameness pain in cattle. The objective of this study was to establish the pharmacokinetic (PK) parameters resulting from intravenous (IV), intramuscular (IM), oral (PO) and transdermal (TD) administration of FM in pre-wean piglets. FM was administered to thirty-nine pre-wean piglets at a target dose of 2.2 mg/kg for IV and IM and 3.3 mg/kg for PO and TD route. Plasma was collected at twenty-seven time points from 0 to 9 days after FM administration and concentrations were determined using ultra-high performance liquid chromatography coupled with mass spectrometry (UPLC-MS). Pharmacokinetic data were analyzed using noncompartmental analysis (NCA) methods and nonlinear mixed-effects (NLME). Initial plasma concentration for IV (C₀) 11,653 μg/L and mean peak plasma concentrations (C_max) 6,543 μg/L (IM), 4,883 μg/L (PO), and 31.5 μg/L (TD) were measured. The time points of peak FM concentrations (t_max) were estimated 30 min, 1 h, and 24 h for IM, PO, and TD, respectively. The bioavailability (F) of PO and IM FM was estimated at >99%, while the bioavailability of TD FM was estimated to be 7.8%. The reported C_max of FM after IM and PO administration is consistent with therapeutic concentration ranges that mitigate pain in other species and adult pigs. However, the low estimated concentration of FM after TD dosing is not expected to mitigate pain in pre-wean piglets. The low F of TD FM suggests that expanding the surface area of application is unlikely to be sufficient to establish an effective TD dose for pain, while the high bioavailability for PO FM should allow for an effective dose regimen to be established.

Pharmacokinetics of thiamphenicol in Japanese quails (Coturnix japonica) after single intravenous and oral administrations

Thiamphenicol (TP) pharmacokinetics were studied in Japanese quails (Coturnix japonica) following a single intravenous (IV) and oral (PO) administration at 30 mg/kg BW. Concentrations of TP were determined with HPLC and were analyzed by a noncompartmental method. After IV injection, elimination half-life (t_1/2λz ), total body clearance (Cl_tot ) volume of distribution at steady state (V_dss ), and mean residence time (MRT) of TP were 3.83 hr, 0.19 L/hr/kg, 0.84 L/kg, and 4.37 hr, respectively. After oral administration of TP, the peak plasma concentration (C_max ) was 19.81 μg/ml and was obtained at 2.00 hr (t_max ) postadministration. Elimination half-life (t_1/2λz ) and mean absorption time (MAT) were 4.01 hr and 1.56 hr, respectively. The systemic bioavailability following oral administration of TP was 78.10%. TP therapy with an oral dosage of 30 mg/kg BW is suggested for a beneficial clinical effect in quails.

The Pharmacokinetics of Medetomidine Administered Subcutaneously during Isoflurane Anaesthesia in Sprague-Dawley Rats

Anaesthetic protocols involving the combined use of a sedative agent, medetomidine, and an anaesthetic agent, isoflurane, are increasingly being used in functional magnetic resonance imaging (fMRI) studies of the rodent brain. Despite the popularity of this combination, a standardised protocol for the combined use of medetomidine and isoflurane has not been established, resulting in inconsistencies in the reported use of these drugs. This study investigated the pharmacokinetic detail required to standardise the use of medetomidine and isoflurane in rat brain fMRI studies. Using mass spectrometry, serum concentrations of medetomidine were determined in Sprague-Dawley rats during medetomidine and isoflurane anaesthesia. The serum concentration of medetomidine for administration with 0.5% (vapouriser setting) isoflurane was found to be 14.4 ng/mL (±3.0 ng/mL). The data suggests that a steady state serum concentration of medetomidine when administered with 0.5% (vapouriser setting) isoflurane can be achieved with an initial subcutaneous (SC) dose of 0.12 mg/kg of medetomidine followed by a 0.08 mg/kg/h SC infusion of medetomidine. Consideration of these results for future studies will facilitate standardisation of medetomidine and isoflurane anaesthetic protocols during fMRI data acquisition.

Direct Comparison of Total Clearance Prediction: Computational Machine Learning Model versus Bottom-Up Approach Using In Vitro Assay

The in vitro-in vivo extrapolation (IVIVE) approach for predicting total plasma clearance (CL_tot) has been widely used to rank order compounds early in discovery. More recently, a computational machine learning approach utilizing physicochemical descriptors and fingerprints calculated from chemical structure information has emerged, enabling virtual predictions even earlier in discovery. Previously, this approach focused more on in vitro intrinsic clearance (CL_int) prediction. Herein, we directly compare these two approaches for predicting CL_tot in rats. A structurally diverse set of 1114 compounds with known in vivo CL_tot, in vitro CL_int, and plasma protein binding was used as the basis for this evaluation. The machine learning models were assessed by validation approaches using the time- and cluster-split training and test sets, and five-fold cross validation. Assessed by five-fold validation, the random forest regression (RF) and radial basis function (RBF) models demonstrated better prediction performance in eight attempted machine learning models. The CL_tot values predicted by the RF and RBF models were within two-fold of the observed values for 67.7 and 71.9% of cluster-split test set compounds, respectively, while the predictivity was worse in the time-split dataset. The predictivity of both models tended to be improved by incorporating in vitro parameters, unbound fraction in plasma (f_u,p), and CL_int. CL_tot prediction utilizing in vitro CL_int and the well-stirred model, correcting for the fraction unbound in blood, was substantially worse compared to machine learning approaches for the same cluster-split test set. The reason that CL_tot is underestimated by IVIVE is not fully explained by considering the calculated microsomal unbound fraction (cf_u,mic), extended clearance classification system (ECCS), and omitting high clearance compounds in excess of hepatic blood flow. The analysis suggests that in silico machine learning models may have the power to reduce reliance on or replace in vitro and in vivo studies for chemical structure optimization in early drug discovery.

Pharmacokinetic Parameters and Estimated Milk Withdrawal Intervals for Domestic Goats (Capra Aegagrus Hircus) After Administration of Single and Multiple Intravenous and Subcutaneous Doses of Flunixin Meglumine

Introduction: The study objectives were to estimate plasma flunixin (FLU) pharmacokinetic parameters and milk depletion profiles for FLU and its metabolite (5-hydroxy flunixin; 5-OH) after subcutaneous (SC) and intravenous (IV) administration of single and multiple flunixin meglumine (FM) doses to non-lactating (nulliparous and pregnant does) and lactating dairy goats. Analytical methods (ELISA and UPLC-MS/MS) for quantifying plasma FLU concentrations were compared. The final objective was to use regulatory (FDA and EMA) methods to estimate milk withdrawal intervals following extra-label drug use in goats.

Methods: FM was administered IV and SC to commercial dairy goats at 1.1 mg/kg for single and multiple doses. Plasma and milk samples were analyzed for FLU and 5-OH via UPLC-MS/MS. Plasma samples were also analyzed for FLU concentrations via ELISA. Using statistical approaches recommended by regulatory agencies, milk withdrawal intervals were estimated following FM extra-label use.

Results: Following IV administration of a single FM dose, clearances were 127, 199, and 365 ml/kg/h for non-lactating (NL) pregnant does, NL nulliparous does, and lactating dairy does, respectively. Following multiple SC doses, clearance/F was 199 ml/kg/h for lactating does. After IV administration of a single FM dose, terminal elimination half-lives were 4.08, 2.87, and 3.77 h for NL pregnant does, NL nulliparous does, and lactating dairy does, respectively. After multiple SC doses, the terminal elimination half-life was 3.03 h for lactating dairy does. No significant differences were noted for samples analyzed by UPLC-MS/MS or ELISA. Milk withdrawal intervals ranged from 36 to 60 h depending on the regulatory statistical method and dosage regimen.

Conclusions: Subcutaneous administration of FM to goats results in similar plasma pharmacokinetic parameters as IV administration. ELISA analysis is an alternative method to UPLC-MS/MS for quantifying FLU concentrations in caprine plasma samples. Following FM extra-label administration to dairy goats, clinicians could consider 36–60 h milk withdrawal intervals.

Population Pharmacokinetics and Pharmacodynamics Modeling of Torasemide and Furosemide After Oral Repeated Administration in Healthy Dogs

Torasemide is a loop diuretic licensed in dogs for cardiogenic pulmonary oedema. The aim of this pharmacokinetic-pharmacodynamic (PK/PD) study was to define an optimally effective dosage regimen based on preclinical data. In a first study, 5 dogs received once-daily oral torasemide (0, 0.1, 0.2, 0.4, 0.8 mg/kg/day) for 14 days. A second study compared once-daily oral torasemide (0, 0.1, 0.2, 0.3, 0.4 mg/kg/day) to twice-daily furosemide (1, 2, 4, 8 mg/kg/day). For all doses of the second study, 11 dogs received a first day of treatment, followed by a 3 day washout and resumed daily treatment for 10 days (until Day 14). Blood and urine were collected to measure urinary torasemide excretion and plasma torasemide concentrations and daily diuresis and natriuresis. Torasemide PK was linear. After rapid absorption (T_max 0.5–1 h), 61% of the bioavailable torasemide was eliminated unchanged in urine. Diuresis and natriuresis observed with torasemide were similar to the ones obtained after furosemide (daily dose-ratios: 1/20 to 1/10). The average diuresis increased from baseline (220 ± 53 mL/day for 10 kg dogs) to 730 ±120 mL after the first torasemide administration and up to 1150 ± 252 mL after 10 administrations at the highest dose. At higher doses (≥0.3 mg/kg/day), daily diureses after 10 diuretic treatment-days were higher than Day 1 and variable between dogs; in contrast, diureses remained constant over time and less variable for doses up to 0.2 mg/kg/day. Natriuresis peaked after the first day and decreased dramatically after the 2nd treatment-day then stabilized to a value close to baseline, except for 0.4 mg/kg/day. Urinary torasemide excretion predicted pharmacodynamics better than plasma concentrations. The decrease in natriuresis observed was successfully modeled using a resistance mechanism; this is likely due to a reabsorption of sodium which did not seem however to affect the volume of urine excreted. For a daily target diuresis of 460 mL/dog/day in severe pulmonary oedema (net fluid loss 240 mL/dog/day), a computed dose of 0.26 mg/kg/day (3.5 mg/kg/day furosemide-equivalent) was selected for clinical studies. Due to high inter-individual variability in diureses at doses ≥0.3 mg/kg, higher doses should be limited to 3–5 days to avoid supra-clinical effects in high responders.

Natural Product Ginsenoside 20(S)-25-Methoxyl-Dammarane-3β, 12β, 20-Triol in Cancer Treatment: A Review of the Pharmacological Mechanisms and Pharmacokinetics

Panax ginseng has been used as an herbal medicine for thousands of years. Most of its pharmacological effects are attributed to its constituent ginsenosides, including 20(S)-25-methoxyl-dammarane-3β, 12β, 20-triol (20(S)-25-OCH₃-PPD), which is one of the protopanaxadiol type ginsenosides. It has been found to exhibit anticancer effects by interacting with multiple pharmacological pathways, such as the Wnt/β-catenin, MDM2, ERK/MAPK, and STAT3 signaling pathways. However, its therapeutic potential could be limited by its low bioavailability mainly due to its low aqueous solubility. Thus, several studies have been conducted on its pharmacokinetics and its delivery systems, so as to increase its oral bioavailability. In this review, comprehensive information on its varying pharmacological pathways in cancer, as well as its pharmacokinetic behavior and pharmaceutical strategies, is provided. This information would be useful in the understanding of its diverse mechanisms and pharmacokinetics as an anticancer drug, leading to the design of superior 20(S)-25-OCH₃-PPD-containing formulations that maximize its therapeutic potential.

Pharmacokinetics of low-dose methotrexate in horses

This study aimed to investigate both the pharmacokinetic behavior and tolerance of methotrexate (MTX) in horses to design a specific dosing regimen as a new immunomodulatory drug for long-term treatment. To determine the primary plasma pharmacokinetic variables after single intravenous, subcutaneous or oral administration, six horses were administered 0.3 mg/kg MTX in a crossover design study. After a 10-week washout, MTX was administered subcutaneously to three of the six previously treated horses at a dose of 0.3 mg/kg once per week for 3 months. In both studies, MTX and metabolite concentrations were measured using LC-MS/MS. The absolute bioavailability of MTX was 73% following subcutaneous administration but less than 1% following oral administration. The plasma clearance was 1.54 ml min^-1  kg^-1 (extraction ratio = 2%). After 24 hr, plasma concentrations were below the LOQ. No adverse effects were noted except for a moderate reversible elevation in liver enzymes (GLDH). With regards to the main metabolites of MTX, very low concentrations of 7-hydroxy-MTX were found, whereas polyglutamated forms (mainly short chains) were found in red blood cells. A subcutaneous dose of 0.2 mg kg^-1  week^-1 may be safe and relevant in horses, although this has yet to be clinically confirmed.

Pharmacokinetic profiles of levofloxacin after intravenous, intramuscular and subcutaneous administration to rabbits (Oryctolagus cuniculus)

Levofloxacin pharmacokinetic profiles were evaluated in 6 healthy female rabbits after intravenous (I/V), intramuscular (I/M), or subcutaneous (S/C) administration routes at a single dose of 5 mg/kg in a 3 × 3 cross-over study. Plasma levofloxacin concentrations were detected using a validated Ultra Performance Liquid Chromatography method with a fluorescence detector. Levofloxacin was quantifiable up to 10 h post-drug administration. Mean AUC0-last values of 9.03 ± 2.66, 9.07 ± 1.80, and 9.28 ± 1.56 mg/h*L were obtained via I/V, I/M, and S/C, respectively. Plasma clearance was 0.6 mL/g*h after I/V administration. Peak plasma concentrations using the I/M and S/C routes were 3.33 ± 0.39 and 2.91 ± 0.56 μg/mL. Bioavailability values, after extravascular administration were complete, - 105% ± 27% (I/M) and 118% ± 40% (S/C). Average extraction ratio of levofloxacin after I/V administration was 7%. Additionally, levofloxacin administration effects on tear production and osmolarity were evaluated. Tear osmolarity decreased within 48 h post-drug administration. All 3 levofloxacin administration routes produced similar pharmacokinetic profiles. The studied dose is unlikely to be effective in rabbits; however, it was calculated that a daily dose of 29 mg/kg appears effective for I/V administration for pathogens with MIC < 0.5 μg/mL.

Evaluation of fluralaner as an oral acaricide to reduce tick infestation in a wild rodent reservoir of Lyme disease

Background

Lyme disease (LD) is an increasing public health threat in temperate zones of the northern hemisphere, yet relatively few methods exist for reducing LD risk in endemic areas. Disrupting the LD transmission cycle in nature is a promising avenue for risk reduction. This experimental study evaluated the efficacy of fluralaner, a recent oral acaricide with a long duration of effect in dogs, for killing Ixodes scapularis ticks in Peromyscus maniculatus mice, a known wildlife reservoir for Borrelia burgdorferi in nature.

Methods

We assigned 87 mice to 3 fluralaner treatment groups (50 mg/kg, 12.5 mg/kg and untreated control) administered as a single oral treatment. Mice were then infested with 20 Ixodes scapularis larvae at 2, 28 and 45 days post-treatment and we measured efficacy as the proportion of infesting larvae that died within 48 h. At each infestation, blood from 3 mice in each treatment group was tested to obtain fluralaner plasma concentrations (C_p).

Results

Treatment with 50 mg/kg and 12.5 mg/kg fluralaner killed 97% and 94% of infesting larvae 2 days post-treatment, but no significant effect of treatment on feeding larvae was observed 28 and 45 days post-treatment. Mouse C_p did not differ significantly between the two tested doses. Mean C_p decreased from 13,000 ng/ml in the 50 mg/kg group and 4000 ng/ml in the 12.5 mg/kg group at Day 2 to < 100 ng/ml in both groups at Day 45.

Conclusions

We provide the first evidence that fluralaner is effective for killing immature ticks in Peromyscus mice, a first step in evaluating its potential for treating wild rodents as a public health intervention to reduce LD risk in endemic areas.

Simple and Rapid Method by Ultra High-Performance Liquid Chromatography (UHPLC) with Ultraviolet Detection for Determination of Efavirenz in Plasma: Application in a Preclinical Pharmacokinetic Study

A simple and rapid ultra-high-performance liquid chromatography (UHPLC) method for determination of efavirenz (EFV) in plasma was developed and applied in a preclinical pharmacokinetic study. The method involves only addition of acetonitrile to precipitation of plasma proteins followed by solvent evaporation. The mobile phase consisted of methanol, acetonitrile and 0.1 M formic acid (20:50:30) at a flow rate of 0.3 mL/min with run time of 5 min. A CSH C18 column and a UHPLC-UV system operating at 245 nm were used. There was a linear response in the range of 0.078 to 10 μg/mL, and the equation was obtained by weighting (1/x2) with r2 = 0.9965. The pharmacokinetic disposition of EFV was investigated in rabbits (two groups, n = 7) following a single intravenous administration (IV group) at a dose of 2.7 mg/kg and a single oral administration (oral group) of EFV co-administered with lamivudine (3TC) and tenofovir (TNF) at a dose of 50, 25 and 25 mg, respectively. The study demonstrated the applicability of the method for determination of EFV in plasma without interference from other co-administered drugs, and the pharmacokinetic parameters were calculated. The method showed advantages over other methods in the literature, such as simplicity of sample processing and fast results.

Pharmacokinetics of marbofloxacin in Green sea turtles (Chelonia mydas) following intravenous and intramuscular administration at two dosage rates

Limited pharmacokinetic information to establish suitable therapeutic plans is available for green sea turtles. Therefore, the present study was conducted to evaluate the pharmacokinetic characteristics of marbofloxacin (MBF) in the green sea turtle, Chelonia mydas, following single intravenous (i.v.) or intramuscular (i.m.) administration at two dosages of 2 and 4 mg/kg body weight (b.w.). Blood samples were collected at assigned times up to 168 hr. MBF in plasma was extracted using liquid-liquid extraction and analyzed by a validated high-performance liquid chromatography (HPLC). MBF was quantifiable from 15 min to 96 hr after i.v. and i.m. administrations at two dose rates. A noncompartmental model was used to fit the plasma concentration of MBF versus time curve for each green sea turtle. The t_1/2λz value, similar for both the dosages (22-28 hr), indicated that the overall rate of elimination of MBF in green sea turtles is relatively slow. The average i.m. F% ranged 88%-103%. MBF is a concentration-dependent drug and the AUC/MIC ratio is the best PK/PD predictor for its efficacy. The MBF dosage of 4 mg/kg appeared to produce an appropriate value of the PK-PD surrogate that predicts antibacterial success for disease caused by susceptible bacteria. In contrast, i.m. administration of MBF at a dosage of 2 mg/kg b.w. was not found to produce a suitable PK-PD surrogate index. However, further studies of multiple doses and plasma binding proteins are warranted to confirm an appropriate dosage regimen.

Scaffold-hopping as a strategy to address metabolic liabilities of aromatic compounds

Understanding and minimizing oxidative metabolism of aromatic compounds is a key hurdle in lead optimization. Metabolic processes not only clear compounds from the body, but they can also transform parent compounds into reactive metabolites. One particularly useful strategy when addressing metabolically labile or oxidation-prone structures is scaffold-hopping. Replacement of an aromatic system with a more electron-deficient ring system can often increase robustness towards cytochrome P450-mediated oxidation while conserving the structural requirements of the pharmacophore. The most common example of this substitution strategy, replacement of a phenyl ring with a pyridyl substituent, is prevalent throughout the literature; however scaffold-hopping encompasses a much wider scope of heterocycle replacement. This review will showcase recent examples where different scaffold-hopping approaches were used to reduce metabolic clearance or block the formation of reactive metabolites. Additionally, we will highlight considerations that should be made to garner the most benefit from a scaffold-hopping strategy for lead optimization.

ADMET profiling of geographically diverse phytochemical using chemoinformatic tools

Aim: Phytocompounds are important due to their uniqueness, however, only few reach the development phase due to their poor pharmacokinetics. Therefore, preassessing the absorption, distribution, metabolism, excretion and toxicity (ADMET) properties is essential in drug discovery. Methodology: Biologically diverse databases (Phytochemica, SerpentinaDB, SANCDB and NuBBE_DB) covering the region of India, Brazil and South Africa were considered to predict the ADMET using chemoinformatic tools (Qikprop, pkCSM and DataWarrior). Results: Screening through each of pharmacokinetic criteria resulted in identification of 24 compounds that adhere to all the ADMET properties. Furthermore, assessment revealed that five have potent anticancer biological activity against cancer cell lines. Conclusion: We have established an open-access database (ADMET-BIS) to enable identification of promising molecules that follow ADMET properties and can be considered for drug development.

Review of the Eprinomectin effective doses required for dairy goats: Where do we go from here?

Eprinomectin (EPM) has been recently granted a marketing authorisation in the European Union for use in goats, with a zero-day milk withdrawal period. Considering the high prevalence of benzimidazole resistance worldwide and the economic implications of managing milk residues, EPM may today be considered the main (or even the only) affordable treatment option, at least in dairy goats in the EU. However, the chosen dose (1 mg/kg) seems to be suboptimal, especially for lactating goats, and the chosen route of administration (Pour-on) highly subject to inter-individual variability. Considering the scarcity of anthelmintic resources, such a dosage regimen might threat the sustainability of this crucial drug in goat milk production and needs to be urgently discussed and reassessed.

In vitro Cytotoxicity and Pharmacokinetic Evaluation of Pharmacological Ascorbate in Dogs

Background: High-dose, pharmacological ascorbate (P-AscH⁻) is preferentially cytotoxic to human cancer cells in vitro. Investigations on the efficacy of P-AscH⁻ as an adjuvant treatment for multiple human cancers are on-going, but has yet to be formally investigated in dogs. The primary objectives of this study were to determine the pharmacokinetic (PK) profile of P-AscH⁻ in healthy Beagle dogs and the effects of P-AscH⁻ on canine osteosarcoma cells in vitro.

Methods: Eight purpose-bred, healthy, spayed female Beagle dogs, between 20 and 21 months old, and 8–10 kg were administered two doses of P-AscH⁻ (550 or 2,200 mg/kg) via intravenous infusion over 6 h, on separate days. Plasma ascorbate concentrations were measured at 12 time points during and after infusion for PK analysis using nonlinear mixed-effects (NLME) and non-compartmental analysis (NCA). Clonogenic assays were performed on 2 canine osteosarcoma cell lines (D-17 and OSCA-8) and canine primary dermal fibroblasts after exposure to high concentrations of ascorbate (75 pmoles/cell).

Results: Plasma ascorbate levels in the dogs peaked at approximately 10 mM following 2,200 mg/kg and returned to baseline 6–8 h after dosing. Minor adverse effects were seen in two dogs. Ascorbate (75 pmoles/cell) significantly decreased survival in both the osteosarcoma cell lines (D-17 63% SD 0.010, P = 0.005; OSCA-8 50% SD 0.086, P = 0.026), compared to normal fibroblasts (27% SD 0.056).

Conclusions: Pharmacological ascorbate is preferentially cytotoxic to canine-derived cancer cells. High levels of ascorbate can be safely administered to dogs. Further studies are needed to determine the effects of P-AscH⁻ on canine patients.

Pharmacokinetic Modeling of Ceftiofur Sodium Using Non-linear Mixed-Effects in Healthy Beagle Dogs

Ceftiofur (CEF) sodium is a third-generation broad-spectrum cephalosporin commonly used in an extra-label manner in dogs for the treatment of respiratory and urinary system infections. To contribute to the literature supporting CEF use in companion animals, we have developed a compartmental, non-linear mixed-effects (NLME) model of CEF pharmacokinetics in dogs (PK). We then used the mathematical model to predict (via Monte Carlo simulation) the duration of time for which plasma concentrations of CEF and its pharmacologically active metabolites remained above minimum inhibitory concentrations (respiratory tract Escherichia coli spp.). Twelve healthy beagle dogs were administered either 2.2 mg/kg ceftiofur-sodium (CEF-Na) intravenously (I.V) or 2.2 mg/kg CEF-Na subcutaneously (S.C). Plasma samples were collected over a period of 72 h post-administration. To produce a measurement of total CEF, both CEF and CEF metabolites were derivatized into desfuroylceftiofur acetamide (DCA) before analysis by UPLC-MS/MS. No adverse effects were reported after I.V or S.C dosing. The NLME PK models were parameterized using the stochastic approximation expectation maximization algorithm as implemented in Monolix 2018R2. A two-compartment mamillary model with first-order elimination and first-order S.C absorption best described the available kinetic data. Final parameter estimates indicate that CEF has a low systemic clearance (0.25 L/h/kg) associated with a low global extraction ratio E = 0.02) and a moderate volume of distribution (2.97 L/kg) in dogs. The absolute bioavailability after S.C administration was high (93.7%). Gender was determined to be a significant covariate in explaining the variability of S.C absorption. Our simulations predicted that a dose of 2.2 mg/kg CEF-Na S.C would produce median plasma concentrations of CEF of at least 0.5 μg/mL (MIC₅₀) for ~30 h.

Pharmacokinetics of Ertapenem in Sheep (Ovis aries) with Experimentally Induced Urinary Tract Infection

Sheep are commonly used as animal models for human biomedical research, but descriptions of their use for studying the pharmacokinetics of carbapenem antimicrobials, such as ertapenem, are unavailable. Ertapenem is a critical antimicrobial for human infections, and the description of the pharmacokinetics of this drug is of value for research using ovine as models for human diseases, such as urinary tract infections (UTI). There are currently no ovine models for comparative biomedical research of UTI. The objective of this study was to report the pharmacokinetics of ertapenem in sheep after single and multiple dosing. In addition, we explored the effects of an immunomodulatory drug (Zelnate) on the pharmacokinetics of ertapenem in sheep. Eight healthy ewes (weight, 64.4 ± 7.7 kg) were used in an ovine bacterial cystitis model of human cystitis with Pseudomonas aeruginosa. After disease confirmation, each ewe received 1 g of ertapenem intravenously once every 24 h for 5 administrations. Blood was collected intensively (14 samples) during 24 h after the first and last administration. After multiple-dose administration, the volume of distribution was 84.5 mL/kg, clearance was 116.3 mL/h/kg, T1/2₍λ_z) was 1.1 h, and the extraction ratio was 0.02. No significant differences in pharmacokinetic parameters or time points were found between groups treated with the immunostimulant and controls or after the 1st or 5th administration of ertapenem. No accumulation was noted from previous administration. Our ovine pharmacokinetic findings can be used to evaluate therapeutic strategies for ertapenem use (varying drug dosing schedules and combinations with other antimicrobials or immune modulators) in the context of UTI.

Physiologically based modelling of the pharmacokinetics of three beta-lactam antibiotics after intra-mammary administration in dairy cows

Understanding the pharmacokinetics of intra-mammary antibiotics is important for the prediction of drug residues in milk and for the design of optimal dosage regimens. Unfortunately, compartmental pharmacokinetic models are not valid for this unique system. A minimal physiologically based pharmacokinetic model is presented incorporating the physiology of milk secretion, drug administration at the quarter level, drug absorption and dispersion, drug retention during the inter-milking interval and episodic drug elimination at milking. The primary objective of the study was the development and exploration of a model for major factors controlling drug concentration in milk, rather than generation of rigorously predictive pharmaco-statistical models for any particular drug. This model was implemented in a two-stage approach, using published concentration data for penicillin, cefuroxime, cephapirin and desacetyl-cephapirin in milk of healthy cows. Model simulations evaluated sensitivity and developed predictions of drug residues. The model successfully predicted both drug concentrations and drug residues in milk. The postmilking residual milk volume did not adequately explain antibiotic pharmacokinetics, requiring additional considerations for drug retention. Local sensitivity analysis indicated that increasing the number of quarters treated, the dosage, or the duration of the inter-milking interval prolonged both the persistence of drug residues and the duration that antibiotic concentration exceeded typical minimum inhibitory concentrations. The model was flexible across different beta-lactam drugs as a general description of intra-mammary pharmacokinetics. This model is suitable for the design and analysis of dosage regimens, and could be applied for the prediction of withholding periods when these antibiotic preparations are used off-label. The final model indicates that explicit consideration of the milking regimen is fundamental to the design and interpretation of pharmacokinetic studies of antibiotics in bovine milk.

Sulfonamide-Based Inhibitors of Biotin Protein Ligase as New Antibiotic Leads

Here, we report the design, synthesis, and evaluation of a series of inhibitors of Staphylococcus aureus BPL (SaBPL), where the central acyl phosphate of the natural intermediate biotinyl-5'-AMP (1) is replaced by a sulfonamide isostere. Acylsulfamide (6) and amino sulfonylurea (7) showed potent in vitro inhibitory activity (K_i = 0.007 ± 0.003 and 0.065 ± 0.03 μM, respectively) and antibacterial activity against S. aureus ATCC49775 with minimum inhibitory concentrations of 0.25 and 4 μg/mL, respectively. Additionally, the bimolecular interactions between the BPL and inhibitors 6 and 7 were defined by X-ray crystallography and molecular dynamics simulations. The high acidity of the sulfonamide linkers of 6 and 7 likely contributes to the enhanced in vitro inhibitory activities by promoting interaction with SaBPL Lys187. Analogues with alkylsulfamide (8), β-ketosulfonamide (9), and β-hydroxysulfonamide (10) isosteres were devoid of significant activity. Binding free energy estimation using computational methods suggests deprotonated 6 and 7 to be the best binders, which is consistent with enzyme assay results. Compound 6 was unstable in whole blood, leading to poor pharmacokinetics. Importantly, 7 has a vastly improved pharmacokinetic profile compared to that of 6 presumably due to the enhanced metabolic stability of the sulfonamide linker moiety.

Concentrations in plasma and selected tissues of marbofloxacin after oral and intravenous administration in Bilgorajska geese (Anser anser domesticus)

Aims: To determine the pharmacokinetics and tissue depletion of 2 mg/kg marbofloxacin (MBX) in Bilgorajska geese (Anser anser domesticus) after I/V and oral administration, to calculate the daily dose from experimental data and to compare it with that calculated by allometric scaling.Methods: Eight clinically normal female Bilgorajska geese were used in a three-phase study with a 3-week wash-out period between phases. In the first phase birds received I/V administration of 2 mg/kg MBX; the same dose was given orally in the second and third phases. Blood samples were collected between 0 minutes and 48 hours in the first and second phases, and samples of liver, kidney, lung, muscle and heart were collected following slaughter of birds between 6 and 48 hours in the third phase. Concentrations of MBX in plasma and tissues were analysed using HPLC. Two additional birds served as controls. The optimal dose was calculated based on a minimal inhibitory concentration (MIC) of 0.125 μg⁄mL using the observed clearance, or using clearance calculated by allometric scaling.Results: Concentrations of MBX in plasma were detectable up to 24 hours following both I/V and oral administration. Mean oral bioavailability was 26.5 (SD 7.7)%. Concentrations of MBX in all tissues were highest at 6 hours and decreased constantly up to 34 hours. The mean optimal daily dose for oral administration of MBX, calculated using the observed clearance was 10.36 (SD 2.18) mg/kg, and using predicted clearance was 5.54 (SD 0.14) mg/kg. The preliminary withdrawal time for a maximum residue limit of 0.15 mg/kg calculated for muscle was 38.4 hours, heart 33.6 hours, kidney 48.3 hours, lung 47.7 hours and liver 49.3 hours.Conclusion and Clinical Relevance: There was insufficient evidence to recommend MBX orally administered to geese at a daily dose of 2 mg⁄kg for treatment of bacteria with an MIC of 0.125 μg/mL. Further pharmacokinetic/pharmacodynamic studies in geese are recommended to determine the MBX dose regimen and its clinical efficacy in geese.