Pharmacokinetic analysis of topotecan after superselective ophthalmic artery infusion and periocular administration in a porcine mode

Purpose: To characterize the vitreous and plasma pharmacokinetics of topotecan after ophthalmic artery infusion (OAI) subsequent to superselective artery catheterization and to compare it with periocular injection (POI). Methods: The ophthalmic artery of 4 pigs was catheterized and 1 mg of topotecan infused over a period of 30 minutes. The contralateral eye was subsequently used for administering topotecan by POI. Serial vitreous specimens were obtained by microdialysis and plasma samples collected and assayed for total and lactone topotecan. Results: Maximum total topotecan concentration in the vitreous (median, range) was significantly higher after OAI compared with POI (131.8 ng/mL [112.9–138.7] vs. 13.6 ng/mL [5.5–15.3], respectively; P , 0.005). Median vitreous exposure calculated as area under the curve for total topotecan attained after OAI was significantly higher than after POI (299.8 nghour/mL [247.6–347.2] and 48.9 nghour/mL [11.8–63.4], respectively; P , 0.05). The vitreous to plasma exposure ratio was 29 after OAI and 3.4 after POI. Systemic exposure for total topotecan was low after both modalities of administration, with a trend to be lower after OAI compared with POI (10.6 nghour/mL [6.8–13.4] vs. 18.7 nghour/mL [6.3–21.7]; P = 0.54). Conclusion: Superselective OAI resulted in significantly higher vitreous concentrations and exposure and a trend toward lower systemic exposure than POI.Fil: Schaiquevich, Paula Susana. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Buitrago, Emiliano. Universidad de Buenos Aires; ArgentinaFil: Ceciliano, Alejandro. No especifíca;Fil: Fandino, Adriana C.. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Asprea, Marcelo. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Sierre, Sergio. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Abramson, David H.. No especifíca;Fil: Bramuglia, Guillermo Federico. Universidad de Buenos Aires; ArgentinaFil: Chantada, Guillermo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; Argentin

Population pharmacokinetics of amikacin in neonatal intensive care unit patients

Background Amikacin treatment requires close monitoring of blood concentrations to increase the probability that levels achieved are both effective and safe. Aims We described population pharmacokinetics parameters of amikacin in newborns from a Neonatal Intensive Care Unit with suspected or documented sepsis. Methods A nonlinear mixed-effect model approach was used to analyse the data. Results Twenty seven neonates were enrolled. Final parameter estimates were: Ke(h-1)=0.232x(CR) Exp-0.85; V(mL/kg)=497. Conclusion Weight and serum creatinine are associated with neonatal amikacin volume of distribution and elimination constant rate, respectively. The presence of sepsis may decrease amikacin elimination, although this observation should be further explored. These results could help to individualize amikacin dosage for neonates

Application of microdialysis for pharmacokinetic-pharmacodynamic modelling

Pharmacokinetic–pharmacodynamic (PK–PD) modelling describes the relationship between the pharmacokinetics and pharmacodynamics of a drug allowing the prediction of clinically relevant parameters. PK–PD modelling has several advantages over classical dose–response studies because it allows a better pharmacodynamic characterisation of drugs and screening of dosage– regimen. However, PK–PD studies are limited by the need for simultaneous measurement of drug tissue levels and corresponding pharmacological effects at multiple time points. The microdialysis technique is a unique research tool that allows the simultaneous determination of unbound concentrations of drugs at several tissues and its action on biochemical and clinical markers during several hours and days. Therefore, microdialysis sampling is an attractive methodology for PK–PD studies. The aim of this review is to describe the applicability of the microdialysis technique for PK–PD modelling of therapeutic agents, including the description of PK–PD modelling concepts, an overview of the microdialysis technique and the analysis of PK–PD studies using microdialysis sampling both in the preclinical and clinical setting.Fil: Höcht, Christian. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; ArgentinaFil: Opezzo, Javier. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; ArgentinaFil: Bramuglia, Guillermo Federico. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; ArgentinaFil: Taira, Carlos Alberto. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentin

Application of Microdialysis in Clinical Pharmacology

Microdialysis has been developed during the last 25 years by several authors primarily to study brain function and changes in levels of endogenous compounds such as neurotransmitters or metabolites in different laboratory animals. However, in the last ten years microdialysis sampling has been introduced as a versatile technique in the clinical setting. Although, microdialysis sampling has been extensively used for metabolic monitoring in patients, it was also employed for the study of distribution of different therapeutic agents especially anti-infective and antineoplasic drugs. In addition, clinical effect of drugs in patients could be also determined by means of microdialysis. So, this article reviewed the vast applications of the microdialysis technique for the study of pharmacokinetic and pharmacodynamic properties of drugs in the clinical setting.Microdialysis has been developed during the last 25 years by several authors primarily to study brain function and changes in levels of endogenous compounds such as neurotransmitters or metabolites in different laboratory animals. However, in the last ten years microdialysis sampling has been introduced as a versatile technique in the clinical setting. Although, microdialysis sampling has been extensively used for metabolic monitoring in patients, it was also employed for the study of distribution of different therapeutic agents especially anti-infective and antineoplasic drugs. In addition, clinical effect of drugs in patients could be also determined by means of microdialysis. So, this article reviewed the vast applications of the microdialysis technique for the study of pharmacokinetic and pharmacodynamic properties of drugs in the clinical setting.Fil: Höcht, Christian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; ArgentinaFil: Opezzo, Javier. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; ArgentinaFil: Bramuglia, Guillermo Federico. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; ArgentinaFil: Taira, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; Argentin

Pharmacokinetic-pharmacodynamic (PK-PD) modeling of cardiovascular effects of metoprolol in spontaneously hypertensive rats: a microdialysis study

The present work addressed possible alterations inthe pharmacokinetics and the in vivo pharmacodynamic ofmetoprolol (MET) in spontaneously hypertensive (SH) ratsand Wistar Kyoto (WKY) animals by means of the microdialysistechnique. The correlation between MET unboundplasma concentrations and its pharmacological effects, such asheart rate and blood pressure change,was also examined in SHand WKY rats by the application of a PK-PD model. METdialysate concentrations and its chronotropic and bloodpressure effect were determined during 3 h after theadministration of 3 and 10 mg.kg−1 of the drug. A PK-PDmodel with a separate effect compartment was used toanalyse the data. A good correlation between plasma METconcentrations and its hypotensive and chronotropic effectwas found in all experimental groups. Although a greatermaximal effect (Emax) for the antihypertensive effect of METwas observed in SH rats (WKY: Emax: −17±1 mmHg; SH:Emax: −28±4 mmHg; P<0.05 versus WKY rats), no differenceswere found in the concentration yielding half-maximalresponse (IC50) comparing SH (IC50: 583±146 ng.ml−1) andWKY animals (IC50: 639±187 ng.ml−1). The bradycardiceffect of MET was greater in SH rats (Emax: −29±1%, P<0.05versus WKY rats) than in WK animals (Emax: −22±2%), butno differences were observed in the IC50 comparing bothexperimental groups (WKY: IC50: 187±53 ng.ml−1; SH: IC50:216±62 ng.ml−1). Pharmacokinetic analysis shows that thevolume of distribution of MET was greater in SH rats (Vd:3.4±0.5 l, P<0.05 versus WKY rats) with regard to WistarKyoto (WKY) animals (Vd: 1.9±0.2 l). The results suggestthat the pharmacokinetic behaviour of metoprolol aremodified in SH rats, resulting in an increased volume ofdistribution. A greater maximal efficacy to the hypotensiveeffect of metoprolol was observed in SH rats, suggestingparticipation of â-adrenoceptors in the maintenance of thehypertension. Also, a greater chronotropic response tometoprolol was found in the hypertensive group comparedwith WKY animals, suggesting that, at least in part, thegreater cardiac effect of metoprolol explained the enhancedhypotensive response of the beta blocker in the SH animals.Fil: Höcht, Christian. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Farmacología; ArgentinaFil: Di Verniero, Carla. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Farmacología; ArgentinaFil: Opezzo, Javier A.. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Farmacología; ArgentinaFil: Bramuglia, Guillermo Federico. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Farmacología; ArgentinaFil: Taira, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Farmacología; Argentin

Ocular pharmacology of topotecan and its activity in retinoblastoma

Purpose: To review the ocular pharmacology and antitumor activity of topotecan for the treatment of retinoblastoma by an evaluation of different routes of administration. Methods: Systematic review of studies available at PubMed using the keywords retinoblastoma, topotecan, and camptothecins, including preclinical data such as cell lines and animal models, as well as clinical studies in patients with retinoblastoma. Results: Forty-two available studies were reviewed. Evidence of antitumor activity against retinoblastoma as a single agent is based on data on cell lines and a limited number of affected patients with intraocular and extraocular disease when given in a protracted schedule. Evidence of additive or synergistic activity in combination with other agents such as carboplatin, melphalan, and vincristine was reported in preclinical and clinical models. In animal models, pharmacokinetic evaluation of topotecan administered by the periocular route shows that most of the drug reaches the vitreous through the systemic circulation. Topotecan administered by intravitreal injection shows high and sustained vitreal concentrations with limited systemic exposure and lack of retinal toxicity at a dose of up to 5 μg. Topotecan administered intraophthalmic artery shows higher passage to the vitreous compared with periocular administration in a swine model. Conclusion: Topotecan alone or in combination is active against retinoblastoma. It shows a favorable passage to the vitreous when given intravenously and intraarterially, and ocular toxicity is minimal by all routes of administration. However, its clinical role, optimal dose, and route of administration for the treatment of retinoblastoma are to be determined.Fil: Schaiquevich, Paula Susana. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría ; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Montero Carcaboso, Angel. Hospital Sant Joan de Déu, Departamento de Oncología; España. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Buitrago, Emiliano. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Farmacología. Cátedra de Farmacología; ArgentinaFil: Taich, Paula Juliana. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría ; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Opezzo, Javier. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Farmacología. Cátedra de Farmacología; ArgentinaFil: Bramuglia, Guillermo Federico. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Farmacología. Cátedra de Farmacología; ArgentinaFil: Chantada, Guillermo Luis. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría ; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Ocular and systemic toxicity of intravitreal topotecan in rabbits for potential treatment of retinoblastoma

Treatment of intraocular retinoblastoma with vitreous seeding is a challenge. Different routes of chemotherapy administration have been explored in order to attaining pharmacological concentrations into the posterior chamber. Intravitreal drug injection is a promissing route for maximum bioavailability to the vitreous but it requires a well defined dose for achieving tumor control while limited toxicity to the retina. Topotecan proved to be a promising agent for retinoblastoma treatment due to its pharmacological activity and limited toxicity. High and prolonged concentrations were achieved in the rabbit vitreous after 5 μg of intravitreal topotecan. However, whether a lower dose could achieve potentially therapeutic levels remained to be determined. Thus, we here study the pharmacokinetics of topotecan after 0.5 μg and the toxicity profile of intravitreal topotecan in the rabbit eye as a potential treatment of retinoblastoma. A cohort of rabbits was used to study topotecan disposition in the vitreous after a single dose of 0.5 μg of intravitreal topotecan. In addition, an independent cohort of non-tumor bearing rabbits was employed to evaluate the clinical and retinal toxicity after four weekly injections of two different doses of intravitreal topotecan (Group A, 5 μg/dose; Group B, 0.5 μg/dose) to the right eye of each animal. The same volume (0.1 ml) of normal saline was administered to the left eye as control. A third group of rabbits (Group C) served as double control (both eyes injected with normal saline). Animals were weekly evaluated for clinical and hematologic values and ocular evaluations were performed with an inverse ophthalmoscope to establish potential topotecan toxicity. Weekly controls included topotecan quantitation in plasma of all rabbits. Electroretinograms (ERGs) were recorded before and after topotecan doses. One week after the last injection, topotecan concentrations were measured in vitreous of all eyes and samples for retinal histology were obtained. Our results indicate that topotecan shows non linear pharmacokinetics after a single intravitreal dose in the range of 0.5–5 μg in the rabbit. Vitreous concentration of lactone topotecan was close to the concentration assumed to be therapeutically active after 5 h of 0.5 μg intravitreal administration. Eyes injected with four weekly doses of topotecan (0.5 or 5 μg/dose) showed no significant differences in their ERG wave amplitudes and implicit times in comparison with control (p > 0.05). Animals showed no weight, hair loss or significant changes in hematologic values during the study period. There were no significant histologic damage of the retinas exposed to topotecan treatments. After intravitreal administration no topotecan could be detected in plasma during the follow-up period nor in the vitreous of treated and control animals after 1 week of the last injection. The present data shows that four weekly intravitreal injection of 5 μg of topotecan is safe for the rabbit eye. Despite multiple injections of 0.5 μg of topotecan are also safe to the rabbit eye, lactone topotecan vitreous concentrations were potentially active only after 5 h of the administration. We postulate promising translation to clinics for retinoblastoma treatment.Fil: Buitagro, Emiliano. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Farmacología; ArgentinaFil: del Sole, Maria Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tandil. Centro de Investigacion Veterinaria de Tandil; ArgentinaFil: Torbidoni, Ana Vanesa. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "juan P. Garrahan". Servicio de Hemato-oncología; ArgentinaFil: Fandino, Adriana. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "juan P. Garrahan"; ArgentinaFil: Asprea, Marcelo. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "juan P. Garrahan"; ArgentinaFil: Croxatto, Juan Oscar. Fundacion Oftalmologia Argentina "j.malbran"; ArgentinaFil: Chantada, Guillermo. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "juan P. Garrahan". Servicio de Hemato-oncología; ArgentinaFil: Bramuglia, Guillermo. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Farmacología; ArgentinaFil: Schaiquevich, Paula Susana. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatria "juan P.garrahan". Unidad de Farmacocinetica Clinica. Laboratorio Farmacia; Argentin

Frequency of CYP3A5 Genetic Polymorphisms and Tacrolimus Pharmacokinetics in Pediatric Liver Transplantation

The evidence available in the pediatric population is limited for making clinical decisions regarding the optimization of tacrolimus (TAC) in pharmacotherapy. The objective of this study was to estimate the frequency of CYP3A5 genetic polymorphisms and their relationship with tacrolimus requirements in the pediatric population. This was a longitudinal cohort study with a two-year follow-up of 77 patients under 18 years old who underwent a liver transplant during the period 2009&ndash;2012 at the J.P. Garrahan Pediatric Hospital. Tacrolimus levels from day five up to two years after the transplant were obtained from hospital records of routine therapeutic drug monitoring. The genotyping of CYP3A5 (CYP3A5*1/*3 or *3/*3) was performed in liver biopsies from both the donor and the recipient. The frequency of CYP3A5*1 expression for recipients was 37.1% and 32.2% for donors. Patients who received an expresser organ showed lower Co/dose, especially following 90 days after the surgery. The role of each polymorphism is different according to the number of days after the transplant, and it must be taken into account to optimize the benefits of TAC therapy during the post-transplant induction and maintenance phases