No description available.

Existing pharmacokinetic monitoring tools for cyclosporine fail to correlate with clinical response. In dogs, pharmacodynamic monitoring of nuclear factor of activated T cell (NFAT) regulated cytokines is thought to provide a better overall evaluation of the immune response to cyclosporine than blood levels; however, such monitoring tools are not available in cats. In this study, we designed and optimized a protocol for maximal T lymphocyte stimulation in cats. This is the first step in the development of a pharmacodynamic monitoring tool for cyclosporine in cats based on expression of NFAT-regulated cytokines. We also confirmed that cyclosporine has anti-lymphocytic properties in cats, and we were the first to document induction of apoptosis by cyclosporine in cats. Differences in individual patient response to cyclosporine may be influenced by apoptotic response of lymphocytes to cyclosporine. Additional studies are required to optimize and validate polymerase chain reaction monitoring of NFAT-regulated cytokines for cyclosporine-mediated immunosuppression.

No description available.

Objective: Dosing intervals of 12 and 24 hours for atenolol have been recommended, but an evidentiary basis is lacking. To test the hypothesis that repeated, once-daily oral administration of atenolol attenuates the heart rate response to isoproterenol for 24 hours, we performed a double-blind, randomized, placebo-controlled cross-over experiment. Animals: Twenty healthy dogs Procedures: Dogs were randomly assigned to receive either placebo (P) and then atenolol (A), [1 mg/kg PO q24h] or vice versa. Treatment periods were 5-7 days; time between periods was 7 days. Heart rates (bpm) at rest (HRr) and during constant rate [0.2 μg/kg/min] infusion of isoproterenol (HRi) were electrocardiographically obtained 0, 0.25, 3, 6, 12, 18, and 24 hours after final administration of drug or placebo. A mixed model ANOVA was used to evaluate the effects of treatment (Tr), time after drug or placebo administration (t), interaction of treatment and time (Tr*t) as well as period and sequence on HRr and HRi. Results: Sequence or period effects were not detected. There was a significant effect of Tr (p <0.0001) and Tr*t (p <0.0001) on HRi. Atenolol significantly attenuated HRi for 24 hours but did so maximally at 3 hours (least squares means ± SE, A: 146±5 bpm, P: 208±5 bpm); the effect at 24 hours was small (A: 193±5, P: 206±5). Atenolol had a small but significant effect (p <0.0001) on HRr. Conclusions and Clinical Relevance: The results of this study support a dosing interval that is less than 24 hours. / MS / This thesis was designed to test the effects of the drug atenolol on heart rate in dogs. Atenolol is used to reduce the heart rate of dogs with cardiovascular disease. The study used 20 dogs that were given oral capsules in both a placebo (no drug) and atenolol phase of the experiment. The study was designed to control for other causes of slower heart rate and make sure that the investigator did not know which treatment was given to a dog. Placebo dogs had a high heart rate response to the drug isoproterenol whereas atenolol treated dogs had a statistically significant lower heart rate response compared to placebo over a 24 hours period of time. The difference between treatments was small after 24 hours and further work is needed to determine the best time interval between doses of medication.

Dicationic diamidines synthesized in the Boykin group a have shown broad range of activity against a wide variety of microbial pathogens such as Cryptosporidium parvum, Leishmania donovani, Plasmodium falciparum, Trypanosoma burcei, and Trichomonas vaginalis. Thiophene based dicationic diamidines have been especially impressive versus Trichomoniasis, and several species of the leishmania parasite. The best compound in vitro against leishmania was 2,5-bis-(4-amidophenyl)thiophene [DB 351]. In an attempt to improve upon antileishmanial activity, several analogs of DB 351 have been synthesized. Previously the central heterocyclic ring has been changed (furan, pyrrole, etc.), and the phenyl has been substituted with a pyridine ring, however, in the thiophene series, the 3 and 4 position of the central thiophene ring has remained unmodified. By modifying the 3 and 4 position of the thiophene ring, and taking advantage of the substituent effect, the pharmacodynamic and distribution properties of DB 351 will altered; hopefully leading to more potent antileishmanial compounds.

Dicationic diamidines synthesized in the Boykin group a have shown broad range of activity against a wide variety of microbial pathogens such as Cryptosporidium parvum, Leishmania donovani, Plasmodium falciparum, Trypanosoma burcei, and Trichomonas vaginalis. Thiophene based dicationic diamidines have been especially impressive versus Trichomoniasis, and several species of the leishmania parasite. The best compound in vitro against leishmania was 2,5-bis-(4-amidophenyl)thiophene [DB 351]. In an attempt to improve upon antileishmanial activity, several analogs of DB 351 have been synthesized. Previously the central heterocyclic ring has been changed (furan, pyrrole, etc.), and the phenyl has been substituted with a pyridine ring, however, in the thiophene series, the 3 and 4 position of the central thiophene ring has remained unmodified. By modifying the 3 and 4 position of the thiophene ring, and taking advantage of the substituent effect, the pharmacodynamic and distribution properties of DB 351 will altered; hopefully leading to more potent antileishmanial compounds.

Introduction. Les corticoïdes sont supposés avoir des effets bénéfiques à faibles doses chez les patients en choc septique réfractaire. Ces effets ont été retrouvés dans plusieurs études utilisant l’hydrocortisone. Mais des données similaires n’existent cependant pas pour la fludrocortisone. Pourtant, l’hypothèse est que ces effets seraient liés en partie à l’action minéralocorticoïde. Or, la fludrocortisone est considérée comme un puissant minéralocorticoïde. Avant une éventuelle évaluation de la fludrocortisone chez les patients en choc septique, il est nécessaire dans un premier temps d’étudier sa pharmacocinétique (PK) et sa relation pharmacocinétique-pharmacodynamique (PK-PD) afin de mieux cerner ses effets et de sélectionner sa posologie efficace. Méthodes. Pour répondre aux objectifs, plusieurs travaux ont été réalisés. La modélisation en pharmacométrie par approche de population a été utilisée dans ces travaux pour caractériser la PK et la relation PK-PD de la fludrocortisone chez des volontaires sains après administration unique et répétée et la PK chez les patients en choc septique. Résultats. Chez les volontaires sains en administration unique seule ou en association avec l’hydrocortisone, la fludrocortisone a montré une demi-vie courte et proche de celle de l’hydrocortisone. Par ailleurs, la fludrocortisone présentait une puissance de l’effet minéralocorticoïde environ 200 fois plus importante que celle de l’hydrocortisone. Les simulations ont montré que la fludrocortisone nécessiterait d’être administrée à raison de quatre fois par jour. Chez les patients en choc septique, l’absorption de la fludrocortisone était très variable (7/21 des patients n’absorbaient pas la molécule) ce qui suggérait la nécessité de mettre au point une forme administrable par voie intraveineuse. A nouveau chez les volontaires sains mais en administration répétée pendant plusieurs jours, la fludrocortisone a montré une demi-vie et des paramètres pharmacocinétiques semblables à ceux retrouvés lors de la première étude et sur le plan pharmacodynamique, des effets hémodynamiques favorables (sur la réactivité vasculaire, la pression artérielle…) montrés pour la première fois avec cette molécule. Conclusion. La fludrocortisone a montré qu’elle pouvait induire les effets biologiques et hémodynamiques recherchés. Les effets hémodynamiques sur la réactivité vasculaire et la pression artérielle ont été observés après une imprégnation de 5 jours d’administration répétée de la fludrocortisone notamment avec la dose de 400 µg/jour. Une évaluation de l’efficacité de la fludrocortisone chez les patients en choc septique et maintenant envisageable et nécessaire pour confirmer les résultats obtenus. / Introduction. Low doses of corticosteroids showed beneficial effects in septic shock patients. These favorable effects may be partly result from the stimulation of the mineralocorticoid receptors. This finding has led us to explore the pharmacokinetic and the effects on hemodynamic and biologic parameters of fludrocortisone which is a potent mineralocorticoid. Methods. In this work, a population approach modeling (nonlinear mixed effects modeling) was used to characterize the pharmacokinetic and the pharmacokinetic-pharmacodynamic relationship of fludrocortisone in healthy volunteers and the pharmacokinetic in septic shock patients. Results. In healthy volunteers after single oral administration alone or in combination with hydrocortisone, fludrocortisone 50 µg showed a short and similar plasma elimination half-life that intravenous hydrocortisone. Fludrocortisone plasma concentrations and effect on urinary sodium/potassium ratio had a higher inter-individual variability as compared to hydrocortisone. Simulations suggested that the administration regimen of fludrocortisone should be reconsidered. In septic shock patient, a single oral dose of fludrocortisone at 50 µg yielded detectable plasma drug concentrations in two-thirds of adults with septic shock. Fludrocortisone pharmacokinetics showed a short plasma elimination half-life and a large inter-individual variability. These results suggested that an intravenous formulation of fludrocortisone would be useful to reduce its pharmacokinetic variability in septic patients. In healthy volunteers again, after 5 days of repeated oral administration, fludrocortisone improved pressor response to phenylephrine. This effect was observed only at the dose of 400 µg/day, suggesting that fludrocortisone at higher doses than previously administered (50 µg/day) may be useful to be effective. Furthermore, we showed that fludrocortisone had a short plasma half-live (1.94 h) which is consistent with our previously published study. After 5 day of repeated administration, fludrocortisone significantly increased blood pressure. This effect was more marked at the dose of 400 µg/day. Conclusion. Our results argue in favor of potential beneficial effects that fludrocortisone could have in septic shock patients. An evaluation of the effectiveness of fludrocortisone in these patients is now possible and necessary to confirm our results.

Most patients with bladder cancer are in the stage of non-muscle-invasive bladder cancer (NMIBC), while 30% of patients progress to the life-threatening muscle-invasive bladder cancer (MIBC) stage because of distant metastases. The selection of treatment options depends on the bladder cancer stage. We established a relationship network for the proteins from the mice urine samples collected during the progression of bladder cancer based on biological pathways and developed population pharmacodynamic models for the proteins in the light of their relationship network. Models that can quantitatively describe changes in the protein profiles of IL1a, IL1b, Csf2, and Casp3 in mice urine samples over time during bladder cancer progression were developed with the consideration of gender differences and progressing age. Our results assist the identification of the early protein diagnostic biomarkers in urine for detecting bladder cancer at its early stages and apply appropriate treatments on patients.

Yes / Adequate drug distribution through tumours is essential for treatment to be effective. Palbociclib is a cyclin-dependent kinase (CDK) 4/6 inhibitor approved for use in patients with hormone receptor (HR) positive, HER2 negative metastatic breast cancer (BC). It has unusual physicochemical properties, which may significantly influence its distribution in tumour tissue. We studied the penetration and distribution of palbociclib in vitro, including the use of multicellular three-dimensional models and mathematical modelling. MCF-7 and DLD-1 cell lines were grown as single cell suspensions (SCS) and spheroids; palbociclib uptake and efflux were studied using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Intracellular concentrations of palbociclib for MCF-7 SCS (Cmax 3.22 µM) and spheroids (Cmax 2.91 µM) were 32 and 29 fold higher and in DLD-1, 13 and 7 fold higher, respectively than the media concentration (0.1 µM). Total palbociclib uptake was lower in DLD-1 cells than MCF-7 cells both in SCS and in spheroids. Both uptake and efflux of palbociclib were slower in spheroids than SCS. These data were used to develop a mathematical model of palbociclib transport that quantifies key parameters determining drug penetration and distribution. The model reproduced qualitatively most features of the experimental data and distinguished between SCS and spheroids, providing additional support for hypotheses derived from the experimental data. Mathematical modelling has the potential for translating in vitro data into clinically relevant estimates of tumour drug concentrations. / Grant for Translational Research and a grant from Leeds NHS Charitable Trustees.

Doctor of Philosophy / Department of Diagnostic Medicine/Pathobiology / Michael D. Apley / The discovery of modern antimicrobials in the early 20th century revolutionized treatment of infectious diseases. Less than 100 years later, antimicrobial resistance has become a global threat to public health. With the rise of antimicrobial resistance, the question that remains to be answered is: Can dosing regimens provide maximal clinical efficacy, yet minimize the development of antimicrobial resistance? A pharmacokinetic / pharmacodynamic approach was utilized to investigate oxytetracycline regimens that would impart efficacy while minimizing the potential for resistance development due to plasmid transfer. An in vitro pharmacodynamic model was used to quantify the response of a Pasteurella multocida isolate to two oxytetracycline dosing regimens. The PK/PD index most closely related to efficacy was the Cmax:MIC. The in vitro pharmacodynamic model was then used to investigate the effects of antimicrobial exposure on plasmid transfer. A mixed population of oxytetracycline-susceptible and resistant bacteria was exposed to two dosing regimens and plasmid transfer was quantified. When oxytetracycline concentrations exceeded the MIC of the recipient, development of resistance was suppressed. The same donor and recipient bacteria were used in an in situ swine model to validate the in vitro findings. Following surgical implantation of porous membrane straws containing the mixed bacterial population, animal subjects in the treatment groups received one of two oxytetracycline treatments. Oxytetracycline concentrations in the plasma and interstitial fluid were quantified. Plasmid transfer within the implant membranes was quantified and correlated to pharmacokinetic measures in the animal. Plasmid transfer rates in the implant membranes did not correlate to the investigated pharmacokinetic parameters. The study methodologies in this dissertation should serve as a foundation for future studies in antimicrobial pharmacokinetic/pharmacodynamic research. The results presented here show that the bacterial response to oxytetracycline can be optimized in a concentration dependent manner and that antimicrobial resistance development through plasmid transfer can be suppressed in vitro when oxytetracycline concentrations exceed the MIC of the recipient bacteria. These results suggest that a proper balance between clinical efficacy and minimizing antimicrobial resistance can be achieved for oxytetracycline through appropriate dosing regimens and drug formulations.