Therapeutic Doses of Eltrombopag do not Inhibit Hepatic BCRP in Healthy Volunteers: Intravenous Ceftriaxone as a Model.

PURPOSE: Ceftriaxone elimination occurs through breast cancer resistance transporter (BCRP) and multidrug resistance-associated protein 2 (MRP-2) which are expressed on the canalicular membrane of hepatocytes. Eltrombopag, a thrombopoetin receptor agonist used in the treatment of immune thrombocytopenic purpura, is reported in in vitro studies as an inhibitor of intestinal BCRP but not an inhibitor of hepatic BCRP. Thus, the present study evaluates the effect of therapeutic doses of eltrombopag on the clinical pharmacokinetics of intravenous ceftriaxone. METHODS: Healthy adult (n=12) were treated with oral doses of eltrombopag (0, 25 or 50 mg) 28 and 4 h prior to intravenous ceftriaxone administration (1g). Serial blood samples were collected up to 48 h after ceftriaxone administration and plasma samples were analysed by LC-MS/MS using 50 µL aliquots (total concentration) and 100 µL (unbound concentration). RESULTS: A method to analyze total and unbound ceftriaxone in plasma using LC-MS/MS was developed and validated with linearity from 1 to 200 µg/mL. Both methods are sensitive, precise and accurate with coefficients of variation less than 15% in the study of inter- and intra-assay precision and accuracy. Ceftriaxone pharmacokinetics in healthy adults were described using a bicompartmental model, with a mean clearance of 0.96 L/h (CI95% 0.71-1.20) and AUC0-∞of 1106 mg.h/mL (CI95% 811-1400) for volunteers that received only ceftriaxone; clearance of 0.95 L/h (CI95% 0.77-1.13) and AUC0-∞ of 1083 mg.h/mL (CI95% 876-1290) for volunteers that received ceftriaxone plus 25 mg of eltrombopag and clearance of 0.96 L/h (CI95% 0.74-1.19) and AUC0-∞ of 1072 mg.h/mL (CI95% 872-1273) for volunteers that received ceftriaxone plus 50 mg of eltrombopag. CONCLUSIONS: The results do not support the existence of a clinical pharmacokinetic drug interaction involving hepatic BCRP in human subjects receiving intravenous ceftriaxone and oral eltrombopag. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

An indirect stereoselective analysis of nebivolol glucuronides in plasma by LC-MS/MS: Application to clinical pharmacokinetics.

Nebivolol is a racemate of the d-isomer responsible for ß1 adrenergic receptor antagonism and the l-isomer responsible for the release of nitric oxide from endothelial cells. Nebivolol is mainly metabolized to nebivolol glucuronide, which also contribute to the nebivolol ß1 adrenoreceptor antagonism. This study reports the development and validation of an indirect stereoselective method of analysis of nebivolol glucuronides in plasma by LC-MS/MS. The method was applied to the investigation of stereoselectivity in the glucuronidation of nebivolol in elderly hypertensive patients (n=11) CYP2D6 phenotyped as EM and treated with a single oral dose of the racemate. One-milliliter plasma aliquots spiked with internal standard (S)-(-)-metoprolol were incubated with 25µL of ß-glucuronidase (final concentration 2500unit/mL) at pH 5.0 for 16h at 37°C. Linearity for total nebivolol was 0.2-125ng of each isomer per mL plasma and permitted analysis of nebivolol glucuronide isomers up to 48h after administration of a single oral dose of 10mg racemate. Regarding to the nebivolol glucuronide isomers, higher plasma concentrations of the d-isomer were observed compared to the l-isomer (d/l AUC=5.4), explaining at least in part the plasma accumulation of unchanged l-nebivolol (l/d AUC=1.8). This study also showed metabolic glucuronide nebivolol/unchanged nebivolol ratios of approximately 6.5 for the l-isomer (AUC 65.3 vs 10.1ngh/mL) and approximately 62.1 (335.2 vs 5.4ngh/mL) for the d-isomer. Considering that d-nebivolol glucuronide also contributes for ß1 adrenergic receptor antagonism, future studies regarding PK-PD of nebivolol should evaluate not only plasma concentrations of unchanged nebivolol isomers but also glucuronide nebivolol isomers.

Stereoselective analysis of nebivolol isomers in human plasma by high-performance liquid chromatography-tandem mass spectrometry: application in pharmacokinetics.

Nebivolol is available for clinical use as a racemic mixture. Isomer d-nebivolol (SRRR) is a ß1 adrenergic receptor blocker and its antipode, l-nebivolol (RSSS) is responsible for endothelium-dependent NO liberation. This report describes the development and validation of a method of analysis of nebivolol isomers in human plasma by high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). Nebivolol isomers were extracted from 2mL aliquots of plasma spiked with tramadol as internal standard, alkalinized and added of sodium chloride and diisopropyl ether:dichloromethane (70:30, v/v). Nebivolol isomers were resolved on a Chirobiotic(®) V column using methanol:acetic acid:diethylamine (100:0.15:0.05, v/v/v) as mobile phase. Protonated ion and respective ion product were monitored in transitions 406>151 for nebivolol and 264>58 for internal standard tramadol. There was no racemization of nebivolol isomers during the procedures of sample preparation and chromatographic analysis and matrix effect was absent. Analysis of nebivolol isomers showed linearity for plasma concentrations of 25-2500pg/mL of each isomer. The quantification limit was 25pg of each isomer/mL of plasma. Variation coefficients and inaccuracy calculated in precision and accuracy determinations were lower than 15%. Nebivolol was stable in human plasma after three successive cycles of freezing and thawing, during 4h at room temperature and after processing during 12h in the auto sampler at 5°C showing deviation values lower than 15%. The method was applied in a study of the kinetic disposition of nebivolol in plasma samples collected until 48h after administration of an oral single dose of 10mg of racemic nebivolol hydrochloride to a patient with systemic arterial hypertension. The clinical study demonstrated that the nebivolol pharmacokinetics is stereoselective. Isomer l-nebivolol showed higher AUC(0-∞) (9.4ng/h/mL vs. 4.7ng/h/mL) and smaller apparent clearance (Cl/f) (531.8L/h vs. 1304.4L/h) when compared to antipode d-nebivolol.

Metoprolol oxidation polymorphism in Brazilian elderly cardiac patients.

OBJECTIVES: The purpose of this study was to phenotype the CYP2D6 in elderly with heart disease classified as extensive metabolizer or poor metabolizers (PM) of metoprolol, develop and validate the method of analysis of metoprolol tartrate and its metabolite in urine using HPLC, and identify potential correlations between anthropometric factors with metabolic ratios of metoprolol/α-OH metoprolol in urine. METHODS: The sample was composed of 130 elderly individuals with a previously identified type of heart condition, with normal renal and hepatic functions. The urine of all the patients were collected 0-8 h after the administration of a pill of 100 mg of metoprolol to determine concentrations of metoprolol and α-hydroxymetoprolol. Those patients presenting a metabolic ratio greater than 12.6 were phenotyped as PM. KEY FINDINGS: The median age of patients was 71.0 years, with a minimum of 60 and maximum of 93 years old. Three patients (2.3%) were phenotyped as PM of metoprolol different from the rate (7-10%) of PM existing in the Caucasian population. CONCLUSIONS: Most of the studied individuals were women, and the proportion of elderly with heart disease classified as PM was smaller than what is usually found among Caucasian populations.

Análise da mortalidade de pacientes hipertensos de unidade pública e especializada na cidade de Ribeirão Preto (SP) / Mortality analysis of hypertensive patients in a public specialized unit, Ribeirão Preto, São Paulo, Brazil

Fundamentos: Estudo publicado em 1967 referente àstaxas anuais de mortalidade, ajustadas por sexo e idade, por enfermidades cardíacas hipertensivas (ECH) por100.000 habitantes, no período de 1962 a 1964, apontava as cidades de Ribeirão Preto (SP) (34,2); São Paulo (SP)(31,7) e Cali, na Colômbia (31,6), como aquelas que apresentavam as maiores taxas por ECH. Objetivo: Estudar as possíveis causas de óbito deindivíduos hipertensos de uma unidade pública de Saúdede Ribeirão Preto (SP).Métodos: Casuística constituída por amostra de hipertensos, de acordo com o JNC VII 2003, dentre os1601 pacientes atendidos em 1999, estando em seguimento clínico no Ambulatório de Cardiologia e Hipertensão Arterial do CSE-FMRP-USP. Foram incluídos no estudo indivíduos adultos, maiores de 20 anos de idade, de ambos os sexos, excluídas as gestantes. Ocorreram 155 óbitos (9,68%) na amostra estudada. Destes, 75 eram mulheres (48,1%) e 80 homens (51,3%). A coleta de dados foi realizada no Instituto Médico Legal, Sistema de Coleta e Análise de Estatísticas Vitais de Ribeirão Preto e Serviço de Verificação de Óbitos do Interior. Resultados: As causas mortis mais frequentes foram: infarto agudo do miocárdio (IAM) (12,9%); septicemia não especificada (11,6%); pneumonia (8,4%); câncer (5,8%); edema agudo de pulmão (5,8%); insuficiência cardíaca congestiva (4,5%); acidente vascular encefálico(4,5%); choque cardiogênico (5,8%); insuficiência respiratória (3,2%); flutter - fibrilação ventricular (2,0%).Conclusão: Percentual significativo de indivíduos que faziam seguimento clínico em unidade pública e especializada de saúde de Ribeirão Preto (SP) teve como principal causa mortis o infarto agudo do miocárdio.