Paclitaxel (Taxol®) is now widely used against breast, ovarian and non-small-cell lung cancer. Anticancer agents generally have narrow therapeutic indices, often with myelosuppression (mainly neutropenia) as dose-limiting side effect. A further complicating factor is that paclitaxel when given as Taxol® has a nonlinear pharmacokinetic (PK) behaviour in plasma. Identifying risk groups more sensitive to chemotherapy due to either a PK or pharmacodynamic (PD) interindividual variability is of importance. The aim of the thesis was to develop predictive mechanism-based PK and PD models applicable for paclitaxel. PK and PK/PD models were developed for patient data from studies with relatively frequent sampling or sparse sampling schedules. Population analyses were performed using the software NONMEM. A pharmacokinetic model describing unbound, total plasma and blood concentrations of paclitaxel from known binding mechanisms was developed and validated. The nonlinear PK in plasma could to a large extent be explained by the micelle forming vehicle Cremophor EL (CrEL) and the unbound drug showed linear PK. Besides a binding component directly proportional to concentrations of CrEL, the model included both linear and nonlinear binding components in plasma and blood. Further, relations between the PK parameters and different demographic factors, including polymorphisms in the cytochrome P450s involved in paclitaxel metabolism, were investigated. A semi-physiological PD model for chemotherapy-induced myelosuppression was developed and applied to different anticancer drugs. The model included a self-renewal for proliferating cells, transit compartments describing the delay in observed myelosuppression and a feedback parameter reflecting the effect on the bone marrow from growth factors that can result in an overshoot in white blood cells. The system-related parameters estimated showed consistency across drugs and the difference in the drug-related parameter reflected the relative bone marrow toxicity of the drugs. Relations between demographic factors and the PD parameters were identified. The developed mechanism-based models promote a better understanding of paclitaxel PK and PD and may be used as tools in dosing individualisation and in development of dosing strategies for new administration forms and new drugs in the same area.

The worldwide increase in antibiotic resistance is a concern for public health. When the appropriate antibiotic dosage is determined, the priorities are efficacy and toxicity. The aim of this thesis was to gain knowledge about the most efficient dosing regimens in order to minimize the emergence and selection of antibiotic-resistant mutants. We also wanted to assess the impact of antibiotic selective pressure and host to host transmission for the dissemination of resistance. Escherichia coli bacteria with different levels of cefotaxime susceptibility were competed in an in vitro kinetic model, demonstrating a complex selection of low-level resistance influenced e.g. by the time duration of selective concentrations and the rise of new mutants. We also constructed a mathematical model incorporating biologically relevant parameters and showed its usefulness when assessing the risks of resistance development. When E. coli populations with pre-existing fluoroquinolone-resistant mutants were exposed to simulated serum concentrations, several currently used doses of fluoroquinolones clearly enhanced the development and selection of resistance. The mutant prevention concentration (MPC) was measured for several E. coli isolates with different fluoroquinolone susceptibilities, and because of fluctuating antibiotic concentrations in the human body, the pharmacokinetics was considered when evaluating MPC. Results indicate that the area under the serum concentration time curve in relation to the MPC may be a useful predictor for emergence of resistance. In the commensal flora of healthy human couples we noted a high frequency of trimethoprim-resistant E. coli. There was also an extensive sharing and transmission of E. coli clones. Treating the female with trimethoprim reduced the number of intestinal E. coli which might have facilitated the transmission from the male partner. These findings suggest that the rate of transmission is high and effectively contributes to the spread of both susceptible and antibiotic-resistant E. coli in intrafamilial settings.

The blood-brain barrier (BBB) controls the movement of substances into and out of the brain. The tight junctions between endothelial cells and energy dependent transporters in the BBB influence rate and extent of drug distribution to the brain. The aim of this thesis was to study different methodological and pharmacokinetic aspects of drug transport at the BBB by characterizing possible active uptake and drug-drug interactions. Therefore, advanced tools for data acquisition and analysis were applied. The role of BBB transport in early drug development, with particular emphasis on in vitro-in vivo comparisons and species differences, was also investigated. Microdialysis in rats was used to study the BBB pharmacokinetics of oxymorphone, diphenhydramine (DPHM), oxycodone and morphine. Oxymorphone, DPHM and verapamil were all found to be actively taken up at the BBB, with brain to blood unbound drug ratios of 2, 5 and 2, respectively. The effect profile for oxycodone was successfully described using the modified M3 method for censored observations. In vitro experiments indicated a competitive interaction between DPHM and oxycodone on active uptake transport to the brain. No such interaction was observed in vivo due to much lower unbound concentrations achieved, compared with the in vitro Ki values. Active uptake of morphine at the BBB was not demonstrated even at very low concentrations as it was not possible to separate the active uptake transport process from active efflux by decreasing the morphine concentration. Mice carrying the human P-gp gene (hMDR1) were used to evaluate possible species differences in P-gp function. Differences were evident between the hMDR1 and normal mice in BBB penetration of various P-gp substrates and in the effect of blockers on P-gp function. Quantitative measurements of P-gp expression levels at the BBB and a comparison with human data are crucial for the future use of the hMDR1 model. In conclusion, this thesis reports active uptake of oxymorphone, DPHM and verapamil at the BBB. In vivo interaction of DPHM and oxycodone at the BBB was found not to be significant at therapeutic drug concentrations. Furthermore species differences were found between human and mouse P-gp function at the BBB.

Advantages and disadvantages of administration of resuscitation fluids in burns patients have been discussed at length. However, the effect of resuscitation fluids on tissue physiological endpoints and tissue antibiotic distribution is scarcely reported, yet clinically crucial. The preliminary studies of this thesis involved evaluation of the literature and the development of a non - recovery anaesthetized rat model of burn injury suitable for the study of plasma and tissue physiological changes and antibiotic pharmacokinetics (PK). Therefore, the first series of the studies for this thesis was designed to examine the relative effects of a range of crystalloid and colloid-containing resuscitation fluids on tissue pH following burn injury in a rat model. The secondary aims were to examine the effects of these fluids on tissue blood flow, plasma protein extravasation (PPE) and evaporative water loss (EWL). In these studies we confirmed that the burn injury and fluid resuscitation were accompanied by a tissue acidosis. Administration of Lactated Ringers’ Albumin (LRA) and Lactated Ringers’ Dextran (LRD) effectively attenuated the degree of tissue acidosis in the thermally injured and non injured sites for 180 minutes post burn and the transepidermal water loss (TEWL) on the non injured sites during the first 60 minutes of the acute phase of burn injury. The second phase of the work was designed to assess the changes in antibiotic distribution with the administration of these different fluids in plasma as well as in interstitial tissues in the burn and the non burn sites. This study showed that for cephalothin (4g/kg body weight, administered intravenously (IV)), Lactated Ringers solution (LR) and Hypertonic Saline (HS) showed similar plasma PK with Time > Minimum inhibitory concentration (MIC) (> 180 minutes) in plasma. However, the antibiotic tissue distribution was more skewed towards lower levels for HS when compared with LR. For piperacillin (18g/kg body weight, administered IV), Time > MIC was considerably low comparatively, being only 55 min for both LR and HS. Antibiotic concentrations did not reach the MIC with LRA resuscitation. When considering the interstitial tissues, Time > MIC for cephalothin was lower than HS with LR on both the burn and the non burn sites. T > MIC for piperacillin was zero for all fluids in both burn and non burn sites. The major finding of this study was that with LRA resuscitation, antibiotic distribution was significantly lower than seen with LR and HS for both antibiotics studied in the interstitial tissue fluid space in both the burn and non burn sites. The final phase of the work was designed to study the apparent permeability co efficient of Keratinocytes (KC) to antibiotics in the presence of simulated pH changes observed in burn tissue in thermal injury using colloids and crystalloids. This study found that there was no significant difference between the basolateral and apical concentrations of antibiotics observed neither with the different pH values nor with time. However, there was definitely a significant difference in the apparent permeability of the cells with LR vs LRA and that the permeability was higher with LR than LRA. This study confirmed that the presence of LR allows greater permeation of the antibiotic into the KC, and also that with LRA resuscitation, the antibiotic tends to stay at higher concentrations in the interstitial compartment. These studies demonstrate that choice of resuscitation fluid following burn injury can affect both changes in tissue physiology and antibiotic distribution, warranting further study in both animal models and patient populations.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / DisfunÃÃo erÃtil (DE) à definida como uma inabilidade para conseguir e manter uma ereÃÃo para satisfaÃÃo sexual. A fentolamina um antagonista a-adrenÃrgico tem sido usado para tratar DE desde 1994, principalmente em combinaÃÃo com outros agentes vasoativos. Mais recentemente uma formulaÃÃo oral mesilato de fentolamina foi desenvolvida para a doenÃa. A droga relaxa corpo cavernoso peniano inibindo a-adrenÃrgicos receptores. Desde o artigo de Traish (1998) se tem especulado que a fentolamina pode relaxar o mÃsculo liso peniano por um mecanismo nÃo adrenÃrgico. O objetivo deste estudo à compreender melhor a farmacocinÃtica da fentolamina (estudo in vivo) usando os dados de um teste de bioequivalÃncia, and investigar sua farmacodinÃmica no corpo cavernoso humano com o propÃsito de dirimir as dÃvidas sobre seu mecanismo nÃo adrenÃrgico neste sÃtio (estudo in vitro). MÃtodos (estudo in vivo): Trinta e seis voluntÃrios sÃos, masculinos, (idade mÃdia 21,5 anos) foram admitidos no estudo cujo desenho consistia de um ensaio duplo cruzado randomizado, com uma Ãnica dose, comparando (regitinaÃ) a uma formulaÃÃo padrÃo de fentolamina (VasomaxÃ). Estudo in vitro: Um total de 64 tiras isoladas de corpo cavernoso humano obtido de 16 doadores cadÃveres masculinos (16 â40 anos de idade) foram investigados. A atividade farmacolÃgica do relaxamento mediado pela fentolamina de fragmentos prÃ-contraÃdos de tecido erÃtil peniano foi estudada em banho de tecidos (meio nÃo adrenÃrgico/nÃo prostanÃide). Resultados (estudo in vivo): a razÃo da mÃdia geomÃtrica de Cmax da formulaÃÃo de Regitinaà 40 mg foi 108.29% (90% CI = 98.58 â 118.96) da formulaÃÃo de Vasomax 40 mg. A razÃo da mÃdia geomÃtrica da [AUC(0-720 min)] da formulaÃÃo de Regitinaà 40 mg foi 102.33 (90% CI = 97.21 â 19= 07.72) da formulaÃÃo de Vasomaxà 40 mg. A mÃdia dos parÃmetros farmacocinÃticos da fentolamina foram Cmax 15,4 ng/mL, Tmax 50 min e t1/2 3 h. (Estudo in vitro): A fentolamina causou relaxamento dependente da concentraÃÃo em tiras de corpo cavernoso humano prÃ-contraÃdas com o agonista a-adrenÃrgico fenilefrina bem como com os agentes nÃo adrenÃrgicos serotonina (10-4 M), prostaglandina F2a (10-4 M) e KCl (60 mM), com a melhor eficÃcia contra a fenilefrina (100% de relaxamento na concentraÃÃo de 10-3 M - IC50 = 1,5 x10-5 M). A Tetrodotoxina (TTX â 10-6 M) (bloqueador de canal de Na+) e atropina (10-5 M) (inibidor do receptor muscarÃnico) nÃo alterou o relaxamento da fentolamina no mÃsculo liso peniano (54,6  4,6% x 48,9 x 6,4%) (52,7  6,5% x 58,6  5,6%) (p > 0,05). O relaxamento da fentolamina nas tiras de corpo cavernoso humano prÃ-contraÃdos com KCl (40 mM) foi significantemente atenuado por NG-nitro-L-arginine L-NAME (10-4 M) ( inibidor da NO sintetase) (59,7  5,8% x 27,8  7,1%) (p < 0,05) e 1H-[1,2,4] Oxadiazole [4,3-a]quinoxalin-1-one ODQ (10-4 M) (inibidor da guanilato ciclase) (62,7  5,1% x 26,8  3,9%) (p < 0,05). O papel dos bloqueadores dos canais de K foram investigados. A glibenclamida (10-4 M) um inibidor do canal de potÃssio ativado por ATP (inibidor do KATP) causou uma inibiÃÃo quase completa (90%) do relaxamento da fentolamina em tiras de corpo cavernoso humano prÃ-contraÃdas com KCl (40 mM) (56,7  6,3% x 11,3  2,3%) (P < 0,05). InvestigaÃÃo com glibenclamida + L-NAME fez o mesmo efeito (54,6  5,6% x 5,7  1,4%) (p < 0,05). Os bloqueadores do canal de potÃssio dependente de CA++ (Kca) Charybdotoxina e apamina nÃo modificaram o relaxamento da fentolamina (54,6  4,6% v 59,3  5,2%) ConclusÃo: Os parÃmetros farmacocinÃticos mÃdios da fentolamina foram similares aos reportados pela literatura cientÃfica. As duas formulaÃÃes da fentolamina foram consideradas semelhantes. Os resultados dos estudos farmacolÃgicos da fentolamina sugerem que ela relaxa o corpo cavernoso de humanos tambÃm por mecanismo nÃo adrenÃrgico-nÃo colinÃrgico, ativando o canal de potÃssio KATP. / Erectile dysfunction (ED) is defined as the Inability to achieve or maintain an erection adequate for sexual satisfaction. Phentolamine an a-adrenergic antagonist has been used to treat ED since 1994, mostly in combination with other vasoactive agents. More recently oral formulation of Phentolamine mesylate were developed for the disease. The drug is thought to relax penile smooth muscle by a inhibition over a-receptors. Since the paper of Traish (1998) has been speculated that phentolamine may also relax penile smooth muscle by a non-adrenergic mechanism. The aim of this study is to understand the pharmacokinetics aspects of Phentolamine (in vivo study) using the data from a bioequivalence test, and to investigate its pharmacodynamics with the purpose to clear its non-adrenergic mechanism in human corpus cavernosum (in vitro study). Methods (In vivo study): Thirty six healthy male volunteers (mean age 21,5 years old) were enrolled in the study that consisted in a single dose, two-way randomized crossover design comparing one phentolamine formulation (regitinaÃ) to one standard phentolamine formulation (VasomaxÃ). In vitro study: A total of 64 isolated human corporeal tissue strips obtained from 16 male donor cadaver (16 â40 years old) were investigate. The pharmacologic activity of phentolamine-mediated relaxation, of pre-contracted erectile tissue strips of human corpus cavernosum were studied in organ bath chambers(non-adrenergic mean). Results: (in vivo study): Regitinaà 40 mg formulation Cmax geometric mean ratio was 108.29% (90% CI = 98.58 â 118.96 of Vasomax 40 mg formulation. Regitineà 40 mg formulation [AUC(0-720 min)] geometric mean ratio was 102.33 (90% CI = 97.21 â 19= 07.72) of Vasomaxà 40 mg formulation. The average phentolamine pharmacokinetics parameters were Cmax 15,4 ng/mL, Tmax 50 min and t1/2 3 h. (In vitro study): Phentolamine caused concentration dependent relaxation in human corpus cavernosum strips pre-contracted with the a-adrenergic agonist phenylephrine as well as with the non-adrenergic serotonin (10-4 M), prostaglandin F2a (10-4 M) and KCl (60 mM) agents, with the best efficacy against phenylephrine (100% of relaxation at 10-3 M - IC50 = 1,5 x10-5M). Tetrodotoxin (TTX â 10-6 M) (Na+ channel blocker) and atropine (10-5 M) (muscarinic receptor inhibitor) did not cause alterations in the phentolamine relaxation of the penile smooth muscle (54,6  4,6% x 48,9 x 6,4%) (52,7  6,5% x 58,6  5,6%) (p > 0,05). The relaxation of phentolamine of the human corpus cavernosum strips pre-contracted with KCl (40 mM) was significantly attenuated by NG-nitro-L-arginine L-NAME (10-4 M) (NO synthase inhibitor) (59,7  5,8% x 27,8  7,1%) (p < 0,05) and 1H-[1,2,4] Oxadiazole [4,3-a]quinoxalin-1-one ODQ (10-4 M) (inibidor da guanilato ciclase (62,7  5,1% x 26,8  3,9%) (p < 0,05). The role of the K channel blockers were investigated. Glibenclamide (10-4 M) an inhibitor of ATP-activated K+ -channels (KATP- inhibitor) caused a almost completely inhibition (90%) of the human corpus cavernosum strips phentolamine relaxation, pre-contracted with KCl (40 mM) (56,7  6,3% x 11,3  2,3%) (P < 0,05). Investigation with Glibenclamide + L-NAME did the same effect (54,6  5,6% x 5,7  1,4%) (p < 0,05). Charybdotoxin and apamin (blockers of CA++-activated K+ channels â Kca) did not alter the phentolamine relaxations (54,6  4,6% v 59,3  5,2%) Conclusion: The average phentolamine pharmacokinetics parameters were similar to the reported by scientific literature. The two drugs are bioequivalents for the rate and extent of absorption. The results from the Pharmacologic studies suggest that Phentolamine relaxes human corpus cavernosum by a nonadrenergic noncholinergic mechanism activating the ATP-activated K+ -channel (KATP).

Le bon usage des antibiotiques en réanimation est un véritable défi. Le sepsis et l’épuration extra-rénale peuvent modifier le comportement des anti-infectieux exposant le patient au risque de sous ou de surdosage. Une meilleure compréhension des altérations liées au sepsis et aux défaillances d’organe permet d’adapter les posologies d’antibiotiques. L’augmentation des posologies d’antibiotiques est nécessaire à la phase initiale du sepsis en raison d’un volume de distribution augmenté. Les adaptations posologiques vont ensuite dépendre des propriétés physico-chimiques de l’anti-infectieux plus que du type d’épuration extra-rénale appliquée. La modélisation pharmacocinétique de population couplée à des simulations de Monte Carlo est une approche pharmaco-statistique élaborée permettant de définir pour une population spécifique les paramètres influençant la PK de l’antibiotique et de prendre en considération la variabilité inter-individuelle. Cette analyse permet également de tester différents schémas posologiques pour un antibiotique donné afin de déterminer la posologie optimale en fonction de différentes fonctions d’organe et selon la susceptibilité des germes traités. La prescription individualisée faisant appel à des logiciels de modélisation PK/PD pourrait permettre à l’avenir d’optimiser l’utilisation des antibiotiques tant en terme d’efficacité que de toxicité tout en limitant l’émergence de résistance. / Prescribing antibiotics in an appropriate way is a massive challenge for the intensivists. Sepsis and renal replacement therapy may alter antibiotics pharmacokinetics exposing critically ill patients to under or overdosing. A better understanding of sepsis and organ failure related alterations could help optimizing antibiotic drug dosing. Increased dosing regimens are often necessary at the early phase of sepsis due to increased volume of distribution. Dosing adjustment will then depend on the physicochemical properties of the anti-infective agent rather than renal replacement therapy modalities. A population pharmacokinetic analysis coupled to Monte Carlo simulations consists in a pharmaco-statistic approach aiming to identify covariates influencing antibiotics PK and to consider inter-individual variability. This analysis allows testing different dosing scenarios to determine the optimal dosing regimen according to different levels of organ dysfunction and according to pathogen susceptibility. Individual drug dosing optimisation, using PK/PD modelling software could improve antibiotic efficacy while limiting antibiotic-related toxicity and antimicrobial resistance.

Les antibiotiques sont actuellement parmi les médicaments les plus utilisés, mais les schémas thérapeutiques optimaux ne sont pas toujours bien définis. Le but de cette thèse était de développer des modèles pharmacocinétiques (PK) et pharmacodynamiques (PK/PD) décrivant les profils de concentrations des antibiotiques ainsi que leurs effets et le développement de résistances bactériennes afin d’optimiser les schémas thérapeutiques.<br/>Un modèle PK de population sur la colistine et sa prodrogue, le colistine methanesulfonate (CMS), a été développé chez les patients recevant la colistine par voie aérosol et/ou sous hémodialyse (HD). Les résultats ont montré un net avantage de la voie aérosol pour le traitement des infections pulmonaires avec une dose de 2 MUI de CMS. Pour les patients sous HD une dose de 1.5 MUI de CMS 2 fois par jour est recommandée avec une dose supplémentaire de 1.5 MUI de CMS après chaque séance de HD.<br/>L’évaluation des performances de différents modèles PK/PD via à une approche par simulation a montré l’importance d’effectuer des études suffisamment longues ainsi que d’obtenir des données microbiologiques complémentaires afin de décrire le développement de la résistance bactérienne.<br/>Un modèle PK/PD incluant taux de mutation et résistance adaptative à la colistine d’une souche bioluminescente de Pseudomonas aeruginosa a été développé à partir de données in-vitro. Une résistance rapide, importante et partiellement réversible a été décrite. Ces résultats confirment l’importance des 24 premières heures dans le traitement des infections, que la colistine seule ne peut pas complétement éliminer les mutants de Pseudomonas aeruginosa et que des associations semblent nécessaires. / Antibiotics are among the most commonly prescribed drugs, however optimal dosages are not yet well defined. The aim of this thesis was to develop pharmacokinetic (PK) and pharmacokinetic-pharmacodynamics (PK/PD) models that characterize the course of antimicrobial drug concentrations and effects over time, with an emphasis on the development of resistance. These models were applied to optimize dosing regimens of antimicrobial therapies.<br/>A population PK model for colistin and its prodrug, colistin methanesulfonate (CMS) was developed in critically ill patients receiving colistin by nebulization and/or undergoing an intermittent hemodialysis (HD). Results predicted clear benefits of using aerosol delivery of 2MIU CMS dose for the treatment of pulmonary infections. For patients with HD session dosing regimen of CMS should be 1.5 MIU twice daily with an additional dose of 1.5 MIU after each HD session.<br/>An assessment of the performances of different PK-PD models by using a simulation approach have shown the importance of longer study designs and of complementary microbiological data to predict accurately bacterial resistance development.<br/> A semi-mechanistic PK/PD model that incorporates mutation rate and adaptive resistance development of a bioluminescent strain of Pseudomonas aeruginosa against colistin was developed based on in-vitro data. A high, quick and partially reversible resistance was described. These results confirm that the first 24 h of treatment are critical in the management of infections, that colistin alone cannot eradicate completely the mutants of Pseudomonas aeruginosa that were selected during the experiments and that combination therapies seem necessary.

La médecine actuelle, basée sur les preuves, et la recherche de standardisation qui l’accompagne, sont-elles compatibles avec la variabilité intra- et interindividuelle de la réponse au traitement observée chez les patients ? Au travers de trois interrogations successives (1- La variabilité est-elle significative en infectiologie ; 2- Peut-on décrire et modéliser cette variabilité ; 3- Comment utiliser ces connaissances pour évaluer l’intérêt de stratégies thérapeutiques), nous montrons qu’il ne semble pas possible d’ignorer cette variabilité, que la modélisation pharmacocinétique-pharmacodynamique permet de la décrire de manière satisfaisante, et que nombre de stratégies thérapeutiques actuelles la prennent insuffisamment en compte. Ces résultats remettent en cause les pratiques actuelles de calculs des posologies, dont l’usage exclusif de covariables, et soulignent l’intérêt du suivi thérapeutique et de l’individualisation des posologies / Are Evidence-Based Medicine and its associated search for standardization compatible with the patient intra- and interindividual variability in therapeutic response? Through three successive questions (1 – Is variability significant in infectious diseases ; 2 – Is it possible to describe and model this variability ; 3 - How can we apply this information to evaluate the usefulness of therapeutic strategies), we show that it does not seem possible to ignore this variability, and that pharmacokinetic-pharmacodynamic modeling can describe it adequately. This study also shows that many current treatment strategies do not take into account this variability sufficiently. These findings challenge the relevance of current practices in drug dosage regimens calculation, including the exclusive use of covariates, and underline the interest of therapeutic drug monitoring and individualized drug therapy

An evidence-based systematic review of elderberry and elderflower (Sambucus nigra) by the Natural Standard Research Collaboration consolidates the safety and efficacy data available in the scientific literature using a validated, reproducible grading rationale. This article includes written and statistical analysis of clinical trials, plus a compilation of expert opinion, folkloric precedent, history, pharmacology, kinetics/dynamics, interactions, adverse effects, toxicology, and dosing.

No description available.