Prevention of rebound effect after natalizumab withdrawal in multiple sclerosis. Study of two high-dose methylprednisolone schedules.

BACKGROUND: Natalizumab (NTZ) is a disease-modifying treatment (DMT) in multiple sclerosis (MS) whose discontinuation can produce a "rebound effect", consisting of severe clinical deterioration and/or evidence of disease reactivation on magnetic resonance imaging (MRI). OBJECTIVE: To analyze the efficacy of two treatment schedules with intravenous methylprednisolone (IVMP) administered during the washout period of natalizumab (i.e., before starting another DMT) in preventing the rebound phenomenon. METHODS: Five-year retrospective study of NTZ withdrawals after at least 24 uninterrupted doses. Two IVMP schedules were tested. In schedule 1 (3-month washout), 1, 2, and 3 g of IVMP were administered on the first, second, and third month respectively. In schedule 2 (2-month washout), 1 and 2 g of IVMP were administered on the first and second month respectively. A new DMT was started 10 days after the end of each schedule. Rebound was defined as at least one clinical relapse plus rebound activity on MRI (>5 gadolinium-enhanced lesions and a number of new/T2-enhanced and/or gadolinium-enhanced lesions greater than before initiation of NTZ) during washout or at 6 months after new DMT initiation (6M-DMT). Clinical and MRI evaluations were performed at 3, 6, 12, and 24 months after initiation of the new DMT. RESULTS: Fifty patients (68% women) were included, with a mean (SD) age of 37.76 (10.88) years and pre-NTZ annualized relapse rate (ARR) of 1.78 (1.04). During NTZ therapy, mean Expanded Disability Status Scale (EDSS) score was 3.7 (1.73) and ARR was 0.23 (0.39). The ARR (mean of both schedules) was 0.1 (0.71) during washout and 0.32 (0.84) at 6M-DMT. Rebound was observed in 10% of cases (n = 5), with no significant clinical or radiological differences (p>0.05) between the two IVMP schedules. Rebound was observed in younger patients and was associated with new MRI lesions and higher ARR at 3M-DMT and 6M-DMT respectively, with no difference in EDSS after 2 years of follow-up. Neither the ARR before NTZ initiation nor the choice of new DMT after NTZ discontinuation was associated with development of rebound effect. CONCLUSIONS: Both IVMP schedules were well tolerated during NTZ washout and rebound was observed in only 10% of cases. In our experience, administration of IVMP during NTZ washout could reduce the possibility of a rebound effect.

Difusión de los antibióticos en el sistema nervioso central / Antibiotic diffusion to central nervous system

Las infecciones del sistema nervioso central (SNC) causadas por patógenos mutiresistentes suponen un reto terapéutico. El paso de fluidos y de solutos al SNC está estrechamente regulado a través de la barrera hematoencefálica (BHE).La penetración de cualquier fármaco, inclusive los antibióticos, en el líquido cefalorraquídeo (LCR) depende del tamaño molecular, la lipofilicidad, la unión a proteínas plasmáticas y su afinidadpor transportadores de la BHE. La relación entre el área bajo la curva en el LCR y el suero AUCCSF (Area Bajo la Curva en LCR) / AUCS (Area Bajo la Curva en suero) de una sustancia es el parámetro más preciso para determinar su capacidad de difusión. Linezolid, algunas quinolonas y metronidazol consiguen altas concentraciones en LCR y son útiles para tratar microorganismos sensibles. Algunos antibióticos cuya permeabilidad a través de la BHE es baja pueden ser administrados directamente en el ventrículo a la vez que se realiza infusión intravenosa. El antibiótico ideal para tratar una infección del SNC es pequeño, no tiene alta tasa de unión a proteínas plasmáticas, es moderadamente lipofílico y no es un ligando de alta afinidad a bombas de expulsión de la BHE. Conocer la farmacocinética de los antibióticos y su interacción con la BHE permitirá mejorar el tratamiento de los pacientes con infecciones del SNC. En este artículo se exponen las propiedades físico-químicas de los principales grupos de antibióticos para evaluar cuáles son más prometedores en el tratamiento de las infecciones del SNC y cómo usarlos en la práctica clínica habitual (AU)

Central nervous system (CNS) infections caused by pathogens with a reduced sensitivity to drugs are a therapeutic challenge. Transport of fluid and solutes is tightly controlled within CNS, where vasculature exhibits a blood-brain barrier (BBB).The entry of drugs, including antibiotics, into the cerebro- spinal fluid (CSF) is governed by molecular size, lipophilicity, plasma protein binding and their affinity to transport systems at the BBB. The ratio of the AUCCSF (Area under the curve in CSF)/AUCS (Area under the curve in serum) is the most accurate parameter to characterize drug penetration into the CSF. Linezolid, some fluoroquinolones and metronidazole get high CSF concentrations and are useful for treating susceptible pathogens. Some highly active antibiotic compounds with low BBB permeability can be directly administered into the ventricles together with concomitant intravenous therapy. The ideal antibiotic to treat CNS infections should be that with a small moderately lipophilic molecule, low plasma protein binding and low affinity to efflux pumps at BBB. Knowledge of the pharmacokinetics and pharmacodynamics of antibiotics at the BBB will assist to optimize antibiotic treatment in CNS infections. This article reviews the physicochemical properties of the main groups of antibiotics to assess which compounds are most promising for the treatment of CNS infections and how to use them in the daily clinical practice (AU)