Therapeutic Dose Range Research Articles

Amelioration of ketamine-induced working memory deficits by dopamine D1 receptor agonists

Ketamine has been used in humans to model cardinal symptoms of schizophrenia, including working memory impairments and behavioral disorganization. Translational studies with ketamine in nonhuman primates promise to extend the neurobiological understanding of this model. By establishing the dose-dependent effects of ketamine on spatial working memory and behavior, we sought to test and compare the capacity of antipsychotic and procognitive agents to reverse these symptoms. Behavioral observations were taken following administration of placebo/ketamine (0.1-1.7 mg/kg, intramuscularly) and animals were tested on the spatial delayed response task 15 min post-injection. Pretreatments with risperidone as well as full and partial D1 receptor agonists were tested for their ability to reverse ketamine-induced impairments. Ketamine (median 1.0 mg/kg) produced a profound cognitive impairment and behavioral sequelae reminiscent of positive and negative symptoms. Risperidone within the therapeutic dose range failed to antagonize behavioral or cognitive consequences of acute ketamine but A77636 (0.1 and 1 microg/kg) and SKF38393 (0.1 microg/kg-100 microg/kg) ameliorated the spatial working memory deficit. This effect of A77636 was blocked by the D1 receptor antagonist, SCH39166 (1 and 10 microg/kg). These findings establish a valuable ketamine platform relevant to the treatment of cognitive dysfunction in schizophrenia. The reversal of ketamine-induced working memory deficits by a D1 receptor agonist, but not a commonly prescribed atypical antipsychotic, provides behavioral evidence for significant D1/N-methyl-D: -aspartate receptor interactions in prefrontal dysfunction and concurs with suggestions that D1 agonists may be useful in the treatment of cognitive impairments in schizophrenia.

Abstract 1673: A pharmacokinetics/pharmacodynamics evaluation of the concentration-QTc relationship of PF-02341066 (PF-1066), an ALK and c-MET/HGFR dual inhibitor administered orally to patients with advanced cancer

Abstract Objective: Assess the potential effect of PF-1066 plasma concentrations on the observed RR corrected QT interval in patients with advanced cancer. Methods: Plasma concentrations of PF-1066 (total drug) and ECG data were collected in study A8081001, an open label, multi-center Phase 1 dose escalation, and safety, pharmacokinetic and exploratory study (J Clin Oncol 27:15s, 2009 (suppl; abstr 3509)). PF-1066 was administered orally on an empty stomach once (QD) or twice (BID) a day in continuous 28-day cycles with doses ranging from 50 mg QD to 300 mg BID. Time-matched, triplicate (≥ 2 minutes apart) ECGs were obtained during the screening period, at pre-dose, 6 hours (∼ Cmax), and 24 hours post-dose on Cycle 1 Day 1, and at pre-dose and 6 hours (∼ Cmax) post-dose on Cycle 1 Day 15 and Cycle 2 Day 1. Baseline ECG data was used to assess which heart rate correction method (QTcB, QTcF and a study specific correction, QTcS) was most appropriate. A linear mixed effects model was used to evaluate the relationship between plasma concentrations and the RR-interval and corrected QT-interval. Results: A total of 62 patients were available for this analysis. The majority of patients had at least 5 triplicate measurements post dose. Fifty-three percent (n=33) were male. Plasma concentrations ranged from 0.228 ng/mL to 1040 ng/mL and the median concentration over all doses was 83.2 ng/mL. At baseline, median heart rate, QTcB- and QTcF-interval were, respectively, 80 bpm, 429 msec and 408 msec. The post-treatment median heart rate, QTcB- and QTcF-interval were, respectively, 73 bpm, 432 msec and 416 msec. The concentration-RR analysis indicates that on average heart rate decreases at approximately 2.5 bpm per 100 ng/mL increase in PF-1066 concentration. QTcS was determined as the most appropriate heart rate correction method for QT-interval. The estimated slope for concentration-QTcS-interval is 0.0076 msec/ng/mL (90% conf. limits: −0.0051, 0203), indicating a small but not statistically significant positive trend in the concentration-QTcS relationship. Based on the model, the average drug associated increase in QTcS is 2.9 msec at the mean Cmax following 250 mg BID dosing. Conclusion: Based on the PK/PD analysis, a clinically relevant QT prolongation is not expected within the therapeutic dose range (up to 250 mg BID) of PF-1066 in patients with advanced cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1673.

Haloperidol and clozapine decrease S100B release from glial cells

Recent meta-analyses showed consistently elevated levels of S100B in serum and cerebrospinal fluid of schizophrenic patients. This finding has been attributed to glial pathology because S100B is produced by astrocytes and oligodendrocytes. However, S100B may be likewise associated with schizophrenia-related disturbances in glial cell as well as adipocyte energy supply and glucose metabolism. The influence of antipsychotic drugs on S100B levels remains unclear, and some studies have suggested that treatment with these drugs may actually contribute to the elevated S100B levels observed in schizophrenic patients. In this study, we explored the effects of the typical antipsychotic haloperidol and the atypical prototype drug clozapine on the release of S100B by astrocytic C6 cells and oligodendrocytic OLN-93 cells. Because of the association between schizophrenia and disturbances in energy metabolism, we assessed the effects of these drugs under basal condition (BC) compared to serum and glucose deprivation (SGD). We found that treatment of C6 and OLN-93 cells with haloperidol and clozapine reduced the release of S100B from C6 and OLN-93 cells under BC and SGD in vitro at a tissue concentration corresponding to the assumed therapeutic dose range of these drugs. These data suggest that elevated levels of S100B in bodily fluids of schizophrenic patients are normalized rather than increased by the effects of antipsychotic drugs on glial cells.

Pre-clinical pharmacokinetics of the cyclooxygenase-inhibiting nitric oxide donor (CINOD) AZD3582

The pre-clinical pharmacokinetics of AZD3582 (4-(nitrooxy)butyl-(2S)-2-(6-methoxy-2-naphthyl) propanoate) and its primary metabolites (naproxen and nitrate) were evaluated. AZD3582 had intermediate and passive intestinal permeability (40 times lower than for naproxen), high systemic plasma clearance (CL), substantial gastrointestinal hydrolysis, intermediate volume of distribution (Vss; >or=3.4 L kg-1) and half-life (t1/2; 7 h), negligible plasma protein binding (approximately 0.1%), low/intermediate oral uptake (>or=13% as intact substance) and low and varying oral bioavailability (mean 1.4% in minipigs and 3.9% in dogs). Following administration of therapeutically relevant oral doses, plasma concentrations of AZD3582 were very low (<or=13 nM in minipigs and <or= 442 nM in dogs; rat data not available) and varying, and accumulation was not apparent. The pharmacokinetics of AZD3582 did not show apparent dose-, time- or gender-related dependency. In blood and intestine, AZD3582 was hydrolysed to naproxen, nitrate and other metabolites. The rate of this conversion was higher in rats than in non-rodents, including man. Despite near-complete to complete uptake of the oral dose, AZD3582 administration resulted in a lower bioavailability (F) of total naproxen than naproxen administration: 55% and 85% relative bioavailability (Frel) in rats and minipigs, respectively. An increased distribution to metabolizing tissues of naproxen (as AZD3582), and thereby enhanced naproxen CL, is believed to be responsible. Following dosing of AZD3582 or naproxen, the t1/2 of naproxen was 5, 9-10 and >40 h in rats, minipigs and dogs, respectively. The Vss and CL for naproxen were small. Plasma protein binding was extensive, and saturation was observed within the therapeutic dose and concentration range. Intake of food prolonged the systemic absorption of naproxen in the minipig. The pharmacokinetics of naproxen did not show apparent time- or gender-related dependency. Following oral dosing of [3H]-, [14C]- and [15N]-AZD3582, most [14C]- and [3H]-activity was excreted in urine and expired air, respectively. Seventeen per cent of [15N] was recovered in minipig urine as [15N]-nitrate. About 30% of [3H]-activity (naproxen and/or naproxen-related metabolites) was excreted in bile and re-absorbed. Concentrations of [14C]-activity (nitrooxy-butyl group and/or its metabolites) in milk were higher than in plasma and [3H]-activity in milk. [3H]- and [14C]-excretion data indicated that intact AZD3582 was not excreted in urine, bile or milk to a significant extent. There was no apparent consistency between tissue distribution of [14C]- and [3H]-activity in the rat, which suggests rapid and extensive metabolism of extravascularly distributed AZD3582. A substantial increase of plasma nitrate levels was found after single and repeated oral doses of AZD3582 in the minipig. No inhibition or induction of CYP450 was found.

A Population Approach to Eplerenone Pharmacokinetics and Saturable Protein Binding

Eplerenone deviates from linear pharmacokinetics at doses above the therapeutic dose range. In addition, saturable protein binding of eplerenone is observed in in vitro plasma protein binding studies. The purpose of the present study was to clarify the factors contributing to the nonlinear pharmacokinetics of eplerenone. Plasma concentration data for eplerenone and its metabolite SC-70303, to which eplerenone is reversibly converted, obtained from four phase I studies were analyzed using NONMEM. A population pharmacokinetic model incorporating protein binding and the reversible relationship between eplerenone and SC-70303 was developed. Models with linear and nonlinear protein binding were fitted to the observed concentration data. The observed concentration data of eplerenone and SC-70303 were best described by a model with nonlinear protein binding. The area under the plasma concentration-time curve of eplerenone simulated by the model increased less than proportionally with increasing dose, whereas that of SC-70303 increased proportionally with increasing dose, consistent with observations from the non-compartmental analysis. In conclusion, the nonlinear pharmacokinetics of eplerenone and the apparently linear pharmacokinetics of SC-70303 were described by applying a model with nonlinear protein binding to observed plasma eplerenone and SC-70303 concentrations, suggesting that nonlinear protein binding plays a role in the nonlinear kinetics.

Ezogabine: A novel antiepileptic as adjunctive therapy for partial onset seizures

Ezogabine (retigabine) is a novel antiepileptic agent which primarily acts to stabilize neuronal potassium-gated ion channels. Currently no other marketed antiepileptic drugs (AEDs) share this mode of action. Ezogabine's pharmacokinetic profile is characterized by rapid absorption and linear, dose-related kinetics across the therapeutic dose range of 600-1200 mg/day. It is not metabolized by the cytochrome P450 system but by N-glucuronidation and N-acetylation. One acetylated metabolite (AWD-21-360) has some minor pharmacological activity as an anticonvulsant. Drug interactions with other AEDs are minimal. Double-blind, randomized, controlled phase II and III trials using ezogabine 600-1200 mg/day as an adjunctive AED for partial onset seizures demonstrate reduced seizure frequencies of approximately 23-44% across the dose range. Long-term open-label extensions up to 12 months demonstrate median seizure reductions of approximately 50% with no signal for tolerance. The most common adverse events, comprising dizziness, somnolence, headache and fatigue, were dose-related and affected the central nervous system.

The Reduced Anticoagulant Effect of Fondaparinux at Low Antithrombin Levels

Low antithrombin levels may compromise the anticoagulant effect of heparin and heparin-related compounds, such as fondaparinux. We compared the anticoagulant effect of 10 concentrations of fondaparinux added to plasma samples with normal range (n = 25, antithrombin 95.4% +/- 9.2%) and low antithrombin (n = 22, antithrombin 45.5% +/- 13.2%) levels, using the Heptest coagulation assay. Heptest clotting time was shorter at any given fondaparinux concentration in the antithrombin-deficient samples, indicating less anticoagulant effect than in the group with normal antithrombin levels. At a high fondaparinux concentration, a saturation effect is observed with no further increase in Heptest clotting time. Addition of antithrombin concentrates results in a shift of the dose-response curve. When antithrombin concentrate was added, Heptest clotting time increased up to a fondaparinux concentration of 10 microg/mL. In the conventional prophylactic and therapeutic dose range, not only treatment with antithrombin concentrates but also an increase in fondaparinux dose normalizes the anticoagulant effect. A saturation effect is observed at high fondaparinux concentrations. Higher levels of antithrombin lead to an exaggerated effect of fondaparinux on Heptest.

6043 Late adverse effects of preoperative hyperfractionated radiation therapy (RT) for advanced rectal cancer

We have studied the molecular effects of a LFD in a murine model in order to better define the biochemical changes associated with folate deficiency. In addition, we have demonstrated the effect of a LFD on the pharmacokinetic profile and therapeutic activity and toxicity of lometrexol. These studies showed increased density of FR in tumors implanted in LFD mice and a decrease in the affinity of these receptors for folic acid. The results suggest that tumors can compensate for low folate bioavailability by up-regulation of a second FR with slightly lower affinity for folic acid. The higher density of this FR would provide greater capacity for garnering serum folate.FPGS activity increased in several tumors and liver and kidney of LFD mice. The increase in this enzyme activity would result in enhanced polyglutamation of folates and classical antifolates and thus increased cellular retention. Consistent with these changes in liver FPGS, mice injected i.v. with a single dose of lometrexol accumulated significantly more drug in liver and tumors of LFD animals compared to SD mice. Also, higher liver concentrations of lometrexol persisted longer in LFD mice. Polyglutamate analysis showed that longer polyglutamate forms appeared earlier in liver of LFD mice. After 7 days, longer polyglutamyl forms were recovered from liver of LFD mice (octa- and hepta-glutamyl lometrexol) compared to those on SD.A comparison of the efficacy and toxicity of lometrexol in C3H mammary tumor-bearing mice showed that in mice on LFD, lometrexol treatment produced a delayed toxicity with an LD50 of 0.1-0.3 mg/kg, a 3000-fold increase in lethality compared to SD mice. Supplementation of mice with folic acid restored anti-tumor activity and increased the therapeutic dose-range over which efficacy could be assessed.These studies support the use of folic acid supplementation for cancer patients treated with antifolate therapy in order to prevent the biochemical changes in FR and FPGS associated with folate deficiency, prevent delayed toxicity to GARFT inhibitors and enhance the therapeutic potential of this class of drugs.

The multiple faces of quercetin in neuroprotection

This review discusses the most recent data on the potential of quercetin to confer neuroprotection. Unfortunately, most of the in vitro studies have used quercetin aglycone, which is not detectable in the plasma or in the brain after oral intake. Moreover, quercetin metabolites and glycosides seem to be less neuroprotective and penetrate the BBB less efficiently than aglycone. Surprisingly, quercetin has beneficial effects on various in vivo models of neural disorders, particularly in cerebrovascular insults; contrasting data also do exist. This may be due to an increase of BBB permeability, described in many of these animal models, which would facilitate quercetin brain penetration. Although quercetin causes no significant toxicity in several animal studies, the risk for neurotoxicity is not negligible because of its narrow therapeutic dose-range in vitro. Notably, this risk may be even higher in the case of increased quercetin access to the brain, which may occur pathologically or artificially (e.g., by liposomal preparations). Based on the referred literature, we doubt that quercetin possesses any significant efficacy in neurodegenerative disorders. Instead, therapeutic trials should focus more on the quercetin efficacy in cerebrovascular insults rather than neurodegeneration.

SU‐FF‐T‐490: The Effect of Daily Cone Beam CT Imaging Dose On the Secondary Cancer Risk for Patients Receiving Prostate IMRT Treatments

Purpose: The impact of daily kilovoltage cone beam CT (CBCT) imaging dose on the radiation induced cancer risk (RICR) was evaluated for patients receiving prostate IMRT treatments. Materials and Methods: Increased secondary cancer risk was modeled by employing effective dose concept described in ICRP report 103 as basis. A prostate IMRT plan was generated in the treatment planning software to calculate dose to organs within the treatment volume. Scattered and leakage dose to organs outside the treatment volume, and CBCT imaging dose were obtained from data in published literature. Both linear and nonlinear risk‐dose response models were considered to establish a relationship between RICR and absorbed dose in the therapeutic dose range. ICRP 103 tissue weighting factors were assumed to stay the constant as a function of absorbed dose. Results: We calculated the relative increase in RICR for various RICR‐dose response models. If the secondary cancer risk was assumed to be proportional to absorbed dose, the increase in RICR due to daily CBCT imaging was in the order of 5%. If the secondary cancer risk was assumed to fall off exponentially at therapeutic doses (beyond 4 Gy), RICR increased by 21%. If RICR was assumed to be constant at therapeutic doses, the increase in RICR was 13%. Finally, if only out‐of‐treatment field organs are considered for risk estimations, RICR increased only 2%. Conclusion: Based on the risk‐dose response models that we evaluated, increased secondary cancer risk due to daily CBCT imaging during prostate IMRT treatments was in the 2% to 21% range. Although such models were known to contain inherently large uncertainties, our study might be a plausible starting point to evaluate the effect of CBCT imaging dose on the secondary cancer risk for radiation therapy patients.

Aminophylline increases ventilation and diaphragm contractility in awake canines

Traditional theophylline bronchodilators are still used clinically, especially in COPD. However, the effect of theophyllines on ventilation and respiratory muscles remains uncertain and these effects have not been measured directly in any awake, intact mammal. We hypothesized that aminophylline in the usual therapeutic dosage range, would elicit in the awake mammal, a significant increase in ventilation, and a significant increase in costal diaphragm shortening and contractility as recorded directly from the muscle. Therefore, we studied 13 awake canines, which had been chronically implanted with fine-wire EMG electrodes and sonomicrometer crystals in the costal segment of the diaphragm. Ventilatory parameters, moving average muscle EMG activity and muscle length and shortening, were measured at baseline and with aminophylline, during resting and hypercapnic stimulated breathing. Experiments were carried out prior to administration of aminophylline (baseline), and 1.5h after loading and ongoing infusion with aminophylline. Minute ventilation, tidal volume and respiratory frequency all increased significantly with aminophylline, both during resting breathing and at equivalent levels of hypercapnic stimulated breathing. Costal diaphragm baseline muscle length was entirely unchanged with aminophylline. Costal diaphragm shortening increased significantly with aminophylline while corresponding costal diaphragm EMG activity remained constant, consistent with increased diaphragm contractility. Thus, in awake, intact mammals, aminophylline in usual therapeutic dosage elicits increased ventilation and increased contractility of respiratory muscles.

Pharmacoutilization of antihypertensive drugs: a model of analysis

To identify clinical and economic indicators of pharmacoutilization of antihypertensive drugs. 4614 subjects receiving a first prescription for amlodipine, atenolol, fosinopril, indapamide, or losartan were included in the study. All prescriptions filled during the study period from January 1, 1997 to December 31, 1998 were considered. A retrospective analysis was carried out on information recorded in the drug database. The percentage of patients continuing, discontinuing, and switching the initial treatment, duration of treatment, and doses used were calculated together with total costs. A large proportion of patients (65.1%) discontinued the treatment. From the analysis of the mean daily dose taken by patients who continued the treatment, it was found that many subjects took a drug dosage which was below the therapeutic dose range, whereas the administration of doses above the therapeutic range occurred only occasionally. Continuation of treatment accounted for 48.1% of total costs, switching accounted for 20.8%, and discontinuation represented 31.1% of total expenditures. With adequate markers, helpful data can be collected for monitoring the quality of antihypertensive drug prescriptions and the rational usage of resources in the general practice setting.

Dosimetric evaluation of sucrose and granulated cane sugar in the therapeutic dose range

Granulated cane sugar has been used as a dosimetric material to report dose in high dose accidental irradiations. The purpose of this study was to assess whether clinical dosimetry is also plausible with such a commonly available material. The behavior of cane sugar was explored with respect to therapeutically relevant radiation quantities (dose, dose rate) and qualities (energy, radiation type) as well as under different temperature conditions. The stability of the signal postirradiation was also measured. Absorbed dose was measured by spectrophotometric readout of a ferrous ammonium sulfate xylenol orange (FX)-sugar solution in 10 cm path length cells. A visible color change was produced as a function of dose when the irradiated sugar samples were dissolved in FX solution (10% dilution by mass). A comparison of the optical absorbance spectra and dose response of cane sugar with analytical grade sucrose was done to establish a benchmark standard from which subsequent dosimetry measurements can be validated. The response of the sugar dosimeter read at 590 nm was found to be linear over the dose range of 100-2000 cGy, independent of energy (6-18 MV) and of the average dose rate (100-500 cGy/min). The readout of sugar samples irradiated with mixed photon and electron fields was also shown to be independent of radiation type (photons and electrons). Sugar temperature (20-40 degrees C) during irradiation did not affect dose estimates, making it a promising dosimeter for in vivo dosimetry, particularly in cases where the dosimeter must remain in contact with the patient for an extended period of time. Sugar can be used as an integrating dosimeter, since it exhibits no fractionation effects. Granulated cane sugar is cost effective, safe, soft tissue equivalent, and can be used under various experimental conditions, making it a suitable dosimeter for some radiotherapy applications.

Effects of imatinib mesylate in osteoblastogenesis

Imatinib mesylate (IM), a tyrosine kinase inhibitor currently used in chronic myeloid leukemia (CML), may also affect the growth of other cellular systems besides CML cells. Because it has been reported that IM may affect bone tissue remodeling, we evaluated the effects of IM on osteoblastic differentiation of human bone marrow mesenchymal stem cells (hBM-MSCs). After 21 days of culture, hBM-MSCs treated with IM (1 microM) alone or osteogenic medium (OM) + IM showed changes in morphology with evidence of extracellular mineralization and increased mRNA expression of osteogenic markers, such as RUNX2, osteocalcin (OCN), and bone morphogenetic protein (BMP-2). We also observed that levels of OCN and the osteoprotegerin (OPG)/receptor activator of nuclear factor-kappa B ligand (RANKL) ratio (OPG/RANKL ratio) were increased in the surnatant of the 21-day culture with IM or OM + IM compared to controls (p<0.005). In addition, we found that in 46 serum samples collected from CML patients treated with IM for 3 to 24 months, the OPG/RANKL ratio increased after 3 and 6 months (p<0.004) returning back to the basal level after 24 months of IM treatment. In these patients, OCN levels were low at diagnosis but they increased throughout the IM treatment, approaching normal levels at 24 months of IM therapy. In summary, our data show that IM increases mRNA expression of osteogenic markers in hBM-MSCs and increases the OPG/RANKL ratio and the OCN levels both in surnatant of hBM-MSCs cultured with IM and in serum of patients treated with IM, thus indicating that IM potentially favors osteoblastogenesis.

Fomepizole: A Critical Assessment of Current Dosing Recommendations

Fomepizole, 4-methylpyrazole (4-MP), is a competitive antagonist of alcohol dehydrogenase with a binding affinity >8000 times that of ethanol. The drug is currently labeled by the United States Food and Drug Administration for the treatment of adult patients with known or suspected ethylene glycol or methanol poisoning. Fomepizole's wide therapeutic dose range and safety profile confer several advantages over standard ethanol therapy for the treatment of toxic alcohol exposures, including the lack of ethanol-associated side effects. Published data and data obtained from the drug's manufacturer implies that the dose escalation after 48 hours is to compensate for fomepizole-induced increased body clearance resulting from autoinduction of the cytochrome P450 (CYP) drug metabolizing enzyme CYP2E1. However, we were unable to identify any evidence of fomepizole's metabolism occurring via CYP2E1 in humans while the data most frequently cited as evidence for induction do not appear to support this claim. Based on this data along with the apparent zero-order kinetics, the current dose increase recommendations may be unnecessary and considering the safety margin described for fomepizole, an extremely conservative constant higher dose administered every 12 hours would appear to assure efficacy and tolerability. Despite the evidence, dose changes should only be implemented after careful clinical trials.

Comparative efficacy and acceptability of 12 new-generation antidepressants: a multiple-treatments meta-analysis

Conventional meta-analyses have shown inconsistent results for efficacy of second-generation antidepressants. We therefore did a multiple-treatments meta-analysis, which accounts for both direct and indirect comparisons, to assess the effects of 12 new-generation antidepressants on major depression. We systematically reviewed 117 randomised controlled trials (25 928 participants) from 1991 up to Nov 30, 2007, which compared any of the following antidepressants at therapeutic dose range for the acute treatment of unipolar major depression in adults: bupropion, citalopram, duloxetine, escitalopram, fluoxetine, fluvoxamine, milnacipran, mirtazapine, paroxetine, reboxetine, sertraline, and venlafaxine. The main outcomes were the proportion of patients who responded to or dropped out of the allocated treatment. Analysis was done on an intention-to-treat basis. Mirtazapine, escitalopram, venlafaxine, and sertraline were significantly more efficacious than duloxetine (odds ratios [OR] 1.39, 1.33, 1.30 and 1.27, respectively), fluoxetine (1.37, 1.32, 1.28, and 1.25, respectively), fluvoxamine (1.41, 1.35, 1.30, and 1.27, respectively), paroxetine (1.35, 1.30, 1.27, and 1.22, respectively), and reboxetine (2.03, 1.95, 1.89, and 1.85, respectively). Reboxetine was significantly less efficacious than all the other antidepressants tested. Escitalopram and sertraline showed the best profile of acceptability, leading to significantly fewer discontinuations than did duloxetine, fluvoxamine, paroxetine, reboxetine, and venlafaxine. Clinically important differences exist between commonly prescribed antidepressants for both efficacy and acceptability in favour of escitalopram and sertraline. Sertraline might be the best choice when starting treatment for moderate to severe major depression in adults because it has the most favourable balance between benefits, acceptability, and acquisition cost.

The significantly enhanced frequency of functional CD4 +CD25 +Foxp3 + T regulatory cells in therapeutic dose aspirin-treated mice

CD4 +CD25 +Foxp3 + regulatory T (Treg) cells, produced in the thymus or periphery as a functionally mature T cell subpopulation, play pivotal roles in maintenance of self-tolerance and negative regulation of immune responses. Aspirin (ASA) is widely used to reduce pain, the risk of cardiovascular diseases and allo-graft rejection. However, the effect of ASA on CD4 +CD25 +Foxp3 + Treg cells has yet to be determined. The frequency, phenotype and immunosuppressive function of CD4 +CD25 +Foxp3 + Treg cells were detected in BALB/c mice treated with low or high doses of ASA for 4 weeks. ASA significantly decreased the percentage and number of CD4 + T cells in the periphery, while ASA remarkably increased the percentage of CD4 +CD25 +Foxp3 + Treg cells in CD4 +T cells. The total cell numbers of thymocytes were significantly decreased in ASA-treated mice, but the number of CD4 + CD25 +Fxop3 + cells and its ratio in CD4 +CD8 − thymocytes were markedly enhanced in the thymi of ASA-treated mice. The phenotype of CD4 +CD25 + Treg cells, including the expressions of CD44, CD45RB, CD62L, CD69, GITR and CTLA-4, did not show detectable changes in ASA-treated mice. CD4 +CD25 + Treg cells in ASA-treated mice exhibited unimpaired immunosuppressive function on CD4 +CD25 − T effector cells. ASA significantly enhanced the frequency of functional CD4 +CD25 +Foxp3 + Treg cells in mice in a therapeutic dose range. The different effects of ASA on CD4 +CD25 +Foxp3 + Treg cells and CD4 +CD25 − T cells may potentially make hosts susceptible to tolerance induction which would be beneficial for tolerance induction in patients with autoimmune diseases or allo-grafts. This study may have potential impacts in the clinical application of ASA.

２．マイクロドーズ臨床試験に必要な非臨床試験データ

Microdose clinical study was introduced to Japan in June 2008 for the purpose of promoting new drug development. However, the upper dose of the study is below 100 μg and the application of findings to drug development is limited. On the other hand, the ICH-M3 guidance “Non-clinical safety studies for the conduct of human clinical trials for pharmaceuticals” was revised in June 2009, which introduces other approaches to exploratory clinical studies. The guidance describes five approaches (two microdose approaches, one sub-therapeutic single dose approach, and two up to therapeutic dose range repeated-dose approaches). Because the highest doses of these studies are limited to within the anticipated non-toxic dose ranges, requirement of toxicity tests is decreased compared to the classic phase 1 study. The rationales for the reduction of toxicity tests are explained.

State-of-the-art mechanisms of intracochlear drug delivery

Treatment of auditory and vestibular dysfunction has become increasingly dependent on inner ear drug delivery. Recent advances in molecular therapy and nanotechnology have pushed development of alternate delivery methodologies involving both transtympanic and direct intracochlear infusions. This review examines recent developments in the field relevant to both clinical and animal research environments. Transtympanic delivery of gentamicin and corticosteroids for the treatment of Meniere's disease and sudden sensorineural hearing loss continues to be clinically relevant, with understanding of pharmacokinetics becoming more closely studied. Stabilizing matrices placed on the round window membrane for sustained passive delivery of compounds offer more controlled dosing profiles than transtympanic injections. Nanoparticles are capable of traversing the round window membrane and cochlear membranous partitions, and may become useful gene delivery platforms. Cochlear and vestibular hair cell regeneration has been demonstrated by vector delivery to the inner ear, offering promise for future advanced therapies. Optimal methods of inner ear drug delivery will depend on toxicity, therapeutic dose range, and characteristics of the agent to be delivered. Advanced therapy development will likely require direct intracochlear delivery with detailed understanding of associated pharmacokinetics.

Time-dependent protective and harmful effects of quercetin on 6-OHDA-induced toxicity in neuronal SH-SY5Y cells

Numerous reports have described the effects of quercetin in models of neurodegenerative diseases, or cancer, resulting in a very complex and sometimes paradoxical picture. Understanding how quercetin causes either protection or cell death in the same model is both tempting and essential. We used the 6-OHDA-induced toxicity model in SH-SY5Y cells, applying graded concentrations of quercetin for a variable time period and following cell viability with MTT-assay and LDH-release as well as caspase-3-like activity. We detected a time-dependent action of quercetin and distinguished an early protective effect from a late toxic one. In addition, we revealed a narrower therapeutic dose-range of quercetin than previously reported in the literature, demonstrating that the toxic effects of quercetin occurred at a concentration only 2-fold higher than the one that produced the greatest protection. We also demonstrated, to our knowledge for the first time, that quercetin itself directly inhibits caspase-3-like activity in a dose-dependent manner. Finally, single doses of quercetin failed to protect against 6-OHDA toxicity in a unilateral rat model of Parkinson's disease. In conclusion, our data may offer an explanation for the dualistic effect of quercetin reported in the literature. In fact, in most studies suggesting quercetin protection against oxidative stressors, the experimental setting failed to include prolonged exposure, and therefore the toxic effects may have been missed. This study supports previous in vivo studies that cast doubt on the efficacy of quercetin against neurodegenerative diseases due to its delayed toxicity.