Intracellular uptake of agents that block the hERG channel can confound the assessment of QT interval prolongation and arrhythmic risk.

BACKGROUND: Oliceridine is a biased ligand at the µ-opioid receptor recently approved for the treatment of acute pain. In a thorough QT study, corrected QT (QTc) prolongation displayed peaks at 2.5 and 60 minutes after a supratherapeutic dose. The mean plasma concentration peaked at 5 minutes, declining rapidly thereafter. OBJECTIVE: The purpose of this study was to examine the basis for the delayed effect of oliceridine to prolong the QTc interval. METHODS: Repolarization parameters and tissue accumulation of oliceridine were evaluated in rabbit left ventricular wedge preparations over a period of 5 hours. The effects of oliceridine on ion channel currents were evaluated in human embryonic kidney and Chinese hamster ovary cells. Quinidine was used as a control. RESULTS: Oliceridine and quinidine produced a progressive prolongation of the QTc interval and action potential duration over a period of 5 hours, paralleling slow progressive tissue uptake of the drugs. Oliceridine caused modest prolongation of these parameters, whereas quinidine produced a prominent prolongation of action potential duration and QTc interval as well as development of early afterdepolarization (after 2 hours), resulting in a high torsades de pointes score. The 50% inhibitory concentration values for the oliceridine inhibition of the rapidly activating delayed rectifier current (human ether a-go-go current) and late sodium channel current were 2.2 and 3.45 µM when assessed after traditional acute exposure but much lower after 3 hours of drug exposure. CONCLUSION: Our findings suggest that a gradual increase of intracellular access of drugs to the hERG channels as a result of their intracellular uptake and accumulation can significantly delay effects on repolarization, thus confounding the assessment of QT interval prolongation and arrhythmic risk when studied acutely. The multi-ion channel effects of oliceridine, late sodium channel current inhibition in particular, point to a low risk of devloping torsades de pointes.

Risk assessment and QbD based optimization of an Eprosartan mesylate nanosuspension: In-vitro characterization, PAMPA and in-vivo assessment.

Quality by design (QbD) principles were implemented to understand the product and process variables of sonoprecipitation technique, for preparation of eprosartan mesylate (EM) nanosuspension. Quality risk management approach was utilized to identify and assess high-risk attributes affecting critical quality attributes (CQA's), prioritizing the number of experiments. The effect of critical material attributes (CMA's) and critical process parameters (CPP's) (soluplus concentration, drug concentration ultrasonication amplitude) on z-average particle size and PDI were investigated using a central composite face-centered design (CCF). Further, design space with criteria set of CMA's and CPP's was established to offer assurance of quality. The optimal formulation, identified using numerical optimization method, was further lyophilized and evaluated for redispersibility, solubility saturation, dissolution kinetic and in-vitro dissolution behavior. The EM nanoparticles were in an amorphous state as confirmed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies. The stability study conducted for a span of 6 months attests physical and chemical stability of EM dry nanosuspension in an amorphous state when stored at 4 °C. The enhanced solubility and in-vitro dissolution of EM nanosuspension may be attributed to the reduced particle size and alteration of the physical state from a crystalline to an amorphous state. Further, the optimized formulation was subjected to in-vitro and ex-vivo transport study using parallel artificial membrane permeability assay (PAMPA) and rat everted gut sac model respectively. The transport studies revealed successful permeation enhancement of EM nanoparticle when compared with EM API and physical mixture (PM). The absolute bioavailability of EM API was 7.1% and improved to 39.9% for EM nanosuspension, suggesting that nanoformulation had overcome solubility and permeability limited bioavailability which was observed with EM API.

Non-clinical safety evaluation and risk assessment to human of aleglitazar, a dual PPAR α/γ agonist, and its major human metabolite.

The non-clinical safety profile of aleglitazar, a peroxisome proliferator activated receptor alpha/gamma agonist, and its major human metabolite M6 was studied in a complete package consisting of drug metabolism and pharmacokinetics characterization, safety pharmacology, genotoxicity, repeat dose toxicity, reproductive toxicity and carcinogenicity studies. These studies identified the following main targets similar to other PPAR agonists: red blood cell parameters, liver, heart, kidney, ovaries, testes, bone marrow, adipose tissue, and fluid accumulation. Additionally, and in the 12-month monkey study only, an increased incidence of generalized hair loss/thinning was observed in all groups including controls. In the rat carcinogenicity study there was no statistically significant increase in tumors. In the mouse carcinogenicity study, there was an increased incidence of angiomatous tumors and there were three males with gallbladder adenoma. No relevant compound-related effects were observed in safety pharmacology, genotoxicity, and a 28-day immunotoxicity rat study. Effects observed in reproductive toxicity studies were similar to those known for other PPARγ agonists. Separate studies with the human metabolite M6 did not reveal findings that would prevent human dosing. Overall, the results from the non-clinical safety studies conducted with aleglitazar and the human metabolite M6 were considered to support the clinical Phase 3 program.

Distribution of the phosphatidylinositol 3-kinase inhibitors Pictilisib (GDC-0941) and GNE-317 in U87 and GS2 intracranial glioblastoma models-assessment by matrix-assisted laser desorption ionization imaging.

Glioblastoma multiforme (GBM) is the most common primary brain tumor in adults, and the limited available treatment options have not meaningfully impacted patient survival in the past decades. Such poor outcomes can be at least partly attributed to the inability of most drugs tested to cross the blood-brain barrier and reach all areas of the glioma. The objectives of these studies were to visualize and compare by matrix-assisted laser desorption ionization (MALDI) imaging mass spectrometry the brain and tumor distribution of the phosphatidylinositol 3-kinase (PI3K) inhibitors pictilisib (GDC-0941, 2-(1H-indazol-4-yl)-6-(4-methanesulfonyl-piperazin-1-ylmethyl)-4-morpholin-4-yl-thieno[3,2-d]pyrimidine) and GNE-317 [5-(6-(3-methoxyoxetan-3-yl)-7-methyl-4-morpholinothieno[3,2-d]pyrimidin-2-yl)pyrimidin-2-amine] in U87 and GS2 orthotopic models of GBM, models that exhibit differing blood-brain barrier characteristics. Following administration to tumor-bearing mice, pictilisib was readily detected within tumors of the contrast-enhancing U87 model whereas it was not located in tumors of the nonenhancing GS2 model. In both GBM models, pictilisib was not detected in the healthy brain. In contrast, GNE-317 was uniformly distributed throughout the brain in the U87 and GS2 models. MALDI imaging revealed also that the pictilisib signal varied regionally by up to 6-fold within the U87 tumors whereas GNE-317 intratumor levels were more homogeneous. Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) analyses of the nontumored half of the brain showed pictilisib had brain-to-plasma ratios lower than 0.03 whereas they were greater than 1 for GNE-317, in agreement with their brain penetration properties. These results in orthotopic models representing either the contrast-enhancing or invasive areas of GBM clearly demonstrate the need for whole-brain distribution to potentially achieve long-term efficacy in GBM.

A clinical and pharmacologic assessment of once-daily versus twice-daily dosing for rivaroxaban.

Altering doses and regimens of a drug has consequences for the drug's pharmacokinetic and pharmacodynamic profile. Based on a half-life of 5-13 h, it is expected that the Factor Xa inhibitor rivaroxaban would be best suited to a twice-daily rather than a once-daily dose regimen. However, although rivaroxaban is used as a twice-daily regimen for the initial treatment of venous thromboembolism (VTE) and secondary prevention after acute coronary syndromes, the approved dosing is once-daily for prevention of VTE after orthopaedic surgery, long-term secondary prevention of VTE and stroke prevention in patients with non-valvular atrial fibrillation. Rivaroxaban dosing was based on the evaluation of the efficacy and safety of several rivaroxaban doses and regimens in phase II trials. A clear overall advantage of twice-daily dosing compared with once-daily dosing was not documented for indications for which once-daily dosing was subsequently selected. Once-daily dosing was therefore selected for these indications because it is expected to be associated with better compliance than twice-daily dosing, and potentially, with improved outcomes. These studies and data obtained with another Factor Xa inhibitor, edoxaban, in addition to previous experience with low molecular weight heparins, indicate that the clinical impact of once-daily versus twice-daily doses on outcome in terms of efficacy and safety cannot be reliably predicted from pharmacology data, e.g. elimination half-life, obtained during pre-clinical and early phase I clinical studies but rather should be ascertained empirically in phase II and III clinical trials.

Prasugrel.

Prasugrel is a third-generation thienopyridine which selectively inhibits the platelet P2Y(12) receptor more rapidly, more potently, and with less interindividual response variability compared with the second-generation thienopyridine clopidogrel. Large-scale phase III clinical testing showed that in high-to moderate-risk acute coronary syndrome patients undergoing percutaneous coronary intervention, prasugrel translates into a greater reduction in ischemic events, including stent thrombosis, in the short and long term compared to clopidogrel. Prasugrel, however, is associated with an increased risk of major bleeding, which is more pronounced in certain patient subgroups. The ideal patient population for prasugrel use are those patients without prior transient ischemic attack/stroke, <75 years of age and >60 kg in whom the greatest ischemic benefit is achieved without a significant increase in major bleeding risk. Dose modifications in specific populations or at given time-points may represent an avenue to minimize bleeding risk and therefore maximize the clinical benefit of prasugrel. Ongoing clinical studies with prasugrel will better define the safety and efficacy profiles of this agent and potentially set the basis for new indications for use.

Duloxetine: a review of its pharmacology and use in chronic pain management.

Duloxetine is a serotonin and norepinephrine reuptake inhibitor that possesses antidepressant and pain-relieving properties. Compared with other antidepressants, it has a high affinity for both norepinephrine and serotonin reuptake transporters, which are relatively balanced. Analgesic onset has been observed within the first week of administration in randomized controlled trials and is likely obtained by enhancing the tone of the descending pain inhibition pathways of the central nervous system. Randomized trials have documented significant analgesic effects for managing chronic pain associated with fibromyalgia and diabetic peripheral neuropathic pain. Studies have also suggested that pain associated with major depressive disorder can be reduced with this medication. Modest effects for headache, osteoarthritic pain, and pain secondary to Parkinson disease have also been documented, but data are obtained from single-blinded or open-label trials that require further corroboration with larger randomized studies. Duloxetine has not yet been directly compared with other antidepressants or anticonvulsants for the treatment of pain syndromes.

Qualitative GC-MS assessment of TCP and TAMORF elimination in rats.

Nerve agents are highly toxic organophosphorus (OP) compounds. They inhibit acetylcholinesterase (AChE), an enzyme that hydrolyses acetycholine (ACh) in the nervous system. Pathophysiological changes caused by OP poisonings are primarily the consequence of surplus ACh on cholinergic receptors and in the central nervous system. Standard treatment of OP poisoning includes combined administration of carbamates, atropine, oximes and anticonvulsants. In order to improve therapy, new compounds have been synthesised and tested. Tenocyclidine (TCP) and its adamantane derivative 1-[2-(2-thienyl)-2-adamantyl] morpholine (TAMORF) have shown interesting properties against soman poisoning. In this study, we developed a qualitative GC-MS method to measure elimination of TCP and TAMORF through rat urine in order to learn more about the mechanisms through which TCP protects an organism from OP poisoning and to determine the duration of this protective effect. GC-MS showed that six hours after treatment with TCP, rat urine contained only its metabolite 1-thienylcyclohexene, while urine of rats treated with TAMORF contained both TAMORF and its metabolites.

An intranasal irritation assessment of antibacterial ointment alone or in combination with mupirocin versus Bactroban Nasal in rabbits.

The purpose of this study was to evaluate the potential irritating effects and the systemic exposure level of an antibacterial ointment containing REP8839 as a single agent or in combination with mupirocin versus Bactroban Nasal in rabbits. Additionally, the reversibility of REP8839 effects during a 14-day recovery period was assessed. Five treatment groups of six male and six female New Zealand White rabbits received dose levels of 1%, 2%, and 4% REP8839, 2% Bactroban Nasal, or 2% REP8839/2% mupirocin combination. One additional group of six animals/sex served as the control and received the vehicle, Petrolatum/Softisan 649. The test article or vehicle was administered to all groups via topical administration to the external nares, twice a day (approx. 8h intervals between the doses) for 21 consecutive days, at a dose volume of 100 microL per nare/dose for a total of 400 microL per day (200 microL per nare). Two animals/sex/group were maintained for a 14-day recovery period. The external nares were reflected back and the mucosal lining was evaluated and scored for erythema and edema within 30-60 min following the first dose each day. Blood samples were collected from all animals at designated time points on Day 21 of the study to assess systemic exposure levels. Cross-sectioning of the nasal tract was conducted in all the groups for microscopic evaluation. Mucosal scoring of the nares did not reveal any edema or erythema in any of the dose groups with the antibacterial alone, with the combination product, or with Bactroban Nasal. Mean body weights and food consumption were not adversely impacted by the test articles. Minimal plasma exposure was observed in the rabbits (<5 ng/mL). The REP8839 groups did appear to have dose-responsive exposure (from below the limit of quantitation to 5 ng/mL with 1%, 2%, and 4% REP8839, respectively). Microscopic changes on the nasal sectioning noted in these animals were infrequent and considered incidental findings unrelated to administration of the test articles. In conclusion doses of up to 4% of REP8839 ointment as a single agent or 2% in the combination product, as well as 2% Bactroban Nasal, were not found to induce mucosal irritation when applied topically to the external nares twice a day for 21 consecutive days. Additionally, no delayed effects were observed in the recovery animals.

Critical review of prasugrel for formulary decision makers.

BACKGROUND: Cardiovascular disease, including acute coronary syndromes (ACS) comprising ST-elevation and non-ST-elevation myocardial infarction (STEMI/NSTEMI) and unstable angina (UA), remains the leading cause of death in the United States. The direct and indirect costs of cardiovascular disease are estimated to surpass $165 billion in 2009. Antiplatelet pharmacotherapy has been shown to reduce ACS-related death and is part of the American College of Chest Physicians (ACCP) and the American College of Cardiology /American Heart Association (ACC/AHA) treatment guideline recommendations. OBJECTIVE: To provide formulary decision makers with information on the pharmacokinetics and pharmacodynamics of the thienopyridine antiplatelet agent prasugrel as well as an analysis of available efficacy and safety data and its risk-benefit profile in comparison with clopidogrel. METHODS: Literature search for information on prasugrel with a focus on (a) the Trial to Assess Improvement in Therapeutic Outcomes by Optimizing Platelet Inhibition with Prasugrel-Thrombolysis in Myocardial Infarction (TRITON-TIMI) 38 trial, (b) briefing documents from the FDA available as of March 1, 2009, and (c) ongoing phase III studies of prasugrel. RESULTS: TRITON-TIMI 38 was a double blind, randomized superiority study involving 13,608 patients with moderate-to high-risk acute coronary syndromes with scheduled percutaneous coronary intervention (PCI). TRITON-TIMI 38 data were available in a published manuscript and in an FDA review. Study patients were randomized to either prasugrel or clopidogrel once daily. The primary end point (composite of death from cardiovascular causes, nonfatal myocardial infarction, or nonfatal stroke) occurred in 643 patients (9.9%) in the prasugrel group and 781 patients (12.1%) in the clopidogrel group (HR = 0.82, 95% CI = 0.73-0.93, P = 0.002). Non-coronary artery bypass graft (non-CABG) TIMI major hemorrhage occurred in 146 patients (2.4%) in the prasugrel group compared with 111 patients (1.8%) in the clopidogrel group (HR=1.32, 95% CI=1.03-1.68, P = 0.03). A subanalysis of the TRITON-TIMI 38 trial data revealed a net harm for patients with a prior history of stroke or transient ischemic attack (TIA) when treated with prasugrel (HR = 1.54, 95% CI = 1.02-2.32, P = 0.04). Combination prasugrel and aspirin is currently being studied in comparison with clopidogrel and aspirin for the treatment of UA/NSTEMI patients that are medically managed. CONCLUSIONS: For every 1,000 patients treated with prasugrel instead of clopidogrel, a total of 24 end points would be prevented at the cost of 10 additional bleeding events. On February 3, 2009, the FDA Cardiovascular and Renal Drugs Advisory Committee deemed this to be an acceptable riskbenefit profile. The committee recommended a label contraindication for patients with prior history of transient ischemic attack or stroke. Treatment versus time analyses demonstrated both early and sustained benefit for prasugrel compared with clopidogrel. However, prasugrel was associated with fewer cardiovascular events prevented per bleeding case the longer the duration of therapy. The study population of TRITON-TIMI 38 was limited to patients undergoing PCI. Managed care decision makers should consider specific criteria limiting prasugrel use to health plan members with characteristics similar to the study population in TRITON-TIMI 38 that benefited from treatment and avoiding use in patients with prior history of stroke or TIA. More data are needed before prasugrel can be recommended in patient groups not addressed by TRITON-TIMI 38.

An assessment of drug-drug interactions: the effect of desvenlafaxine and duloxetine on the pharmacokinetics of the CYP2D6 probe desipramine in healthy subjects.

A number of antidepressants inhibit the activity of the cytochrome P450 2D6 enzyme system, which can lead to drug-drug interactions. Based on its metabolic profile, desvenlafaxine, administered as desvenlafaxine succinate, a new serotonin-norepinephrine reuptake inhibitor, is not expected to have an impact on activity of CYP2D6. This single-center, randomized, open-label, four-period, crossover study was undertaken to evaluate the effect of multiple doses of desvenlafaxine (100 mg/day, twice the recommended therapeutic dose for major depressive disorder in the United States) and duloxetine (30 mg b.i.d.) on the pharmacokinetics (PK) of a single dose of desipramine (50 mg). A single dose of desipramine was given first to assess its PK. Desvenlafaxine or duloxetine was then administered, in a crossover design, so that steady-state levels were achieved; a single dose of desipramine was then coadministered. The geometric least-square mean ratios (coadministration versus desipramine alone) for area under the plasma concentration versus time curve (AUC) and peak plasma concentrations (C(max)) of desipramine and 2-hydroxydesipramine were compared using analysis of variance. Relative to desipramine alone, increases in AUC and C(max) of desipramine associated with duloxetine administration (122 and 63%, respectively) were significantly greater than those associated with desvenlafaxine (22 and 19%, respectively; P < 0.001). Duloxetine coadministered with desipramine was also associated with a decrease in 2-hydroxydesipramine C(max) that was significant compared with the small increase seen with desvenlafaxine and desipramine (-24 versus 9%; P < 0.001); the difference between changes in 2-hydroxydesipramine AUC did not reach statistical significance (P = 0.054). Overall, desvenlafaxine had a minimal impact on the PK of desipramine compared with duloxetine, suggesting a lower risk for CYP2D6-mediated drug interactions.

An assessment of the in vivo efficacy of the glycogen phosphorylase inhibitor GPi688 in rat models of hyperglycaemia.

BACKGROUND AND PURPOSE: Studies in cultured hepatocytes demonstrate glycogen synthase (GS) activation with glycogen phosphorylase (GP) inhibitors. The current study investigated whether these phenomena occurred in vivo using a novel GP inhibitor. EXPERIMENTAL APPROACH: An allosteric GP inhibitor, GPi688, was evaluated against both glucagon-mediated hyperglycaemia and oral glucose challenge-mediated hyperglycaemia to determine the relative effects against GP and GS in vivo. KEY RESULTS: In rat primary hepatocytes, GPi688 inhibited glucagons-mediated glucose output in a concentration dependent manner. Additionally GP activity was reduced and GS activity increased seven-fold. GPi688 inhibited glucagon-mediated hyperglycaemia in both Wistar (65%) & obese Zucker (100%) rats and demonstrated a long duration of action in the Zucker rat. The in vivo efficacy in the glucagon challenge model could be predicted by the equation; % glucagon inhibition=56.9+34.3[log ([free plasma]/rat IC50)], r=0.921). GPi688 also reduced the blood glucose of obese Zucker rats after a 7 h fast by 23%. In an oral glucose tolerance test in Zucker rats, however, GPi688 was less efficacious (7% reduction) than a glycogen synthase kinase-3 (GSK-3) inhibitor (22% reduction), despite also observing activation (by 45%) of GS in vivo. CONCLUSIONS AND IMPLICATIONS: Although GP inhibition can inhibit hyperglycaemia mediated by increased glucose production, the degree of GS activation induced by allosteric GP inhibitors in vivo, although discernible, is insufficient to increase glucose disposal. The data suggests that GP inhibitors might be more effective clinically against fasting rather than prandial hyperglycaemic control.

In vitro metabolism of indiplon and an assessment of its drug interaction potential.

This study was designed to study the in vitro metabolism of indiplon, a novel hypnotic agent, and to assess its potential to cause drug interactions. In incubations with pooled human liver microsomes, indiplon was converted to two major, pharmacologically inactive metabolites, N-desmethyl-indiplon and N-desacetyl-indiplon. The N-deacetylation reaction did not require NADPH, and appeared to be catalyzed by organophosphate-sensitive microsomal carboxylesterases. The N-demethylation of indiplon was catalyzed by CYP3A4/5 based on the following observations: (1) the sample-to-sample variation in N-demethylation of indiplon ([S] = 100 microM) in a bank of human liver microsomes was strongly correlated with testosterone 6beta-hydroxylase (CYP3A4/5) activity (r(2) = 0.98), but not with any other CYP enzyme; (2) recombinant CYP1A1, CYP1A2, CYP3A4, CYP3A5 and CYP3A7 had the ability to catalyze this reaction; (3) the N-demethylation of indiplon was inhibited by CYP3A4/5 inhibitors (ketoconazole and troleandomycin), but not by a CYP1A2 inhibitor (furafylline). In pooled human liver microsomes, indiplon exhibited a weak capacity to inhibit CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2D6, CYP2E1, CYP3A4/5 and carboxylesterase (p-nitrophenylacetate hydrolysis) activities (IC50 >/= 20 microM). Clinical data available on indiplon support the conclusions of this paper that the in vitro metabolism of indiplon is catalyzed by multiple enzymes, and indiplon is a weak inhibitor of human CYP enzymes.

Determination of duloxetine in human plasma via LC/MS and subsequent application to a pharmacokinetic study in healthy Chinese volunteers.

BACKGROUND: The pharmacokinetics of duloxetine hydrochloride have been well studied after its approval for clinical use. However, few such data have been reported in the English language literature. We developed a method to determine the pharmacokinetics of duloxetine enteric-coated capsules in healthy Chinese volunteers. METHODS: A rapid and sensitive liquid chromatography-mass spectrometric (LC/MS) method for the determination of duloxetine in human plasma using flupentixol as the internal standard (I.S.) was developed and validated. Sample preparation of the plasma involved deproteination with acetonitrile twice, repeatedly. Samples were then analyzed by HPLC on a Thermo Hypersil-Hypurity C18 column (150 x 2.1 mm, 5 microm). A single-quadrupole mass spectrometer with an electrospray interface was operated in the selected-ion monitoring mode to detect the [M+H](+) ions at 298 m/z for duloxetine and at 435 m/z for the internal standard. RESULTS: Pharmacokinetics were measured in 12 healthy Chinese male volunteers (6 males and 6 females) who received a single regimen with 3 different dosages at 22.4, 44.8 and 67.2 mg of duloxetine enteric-coated capsules. CONCLUSION: A sensitive and specific method for quantifying duloxetine levels in human plasma has been devised and successfully applied to a clinic pharmacokinetic study of an enteric-coated capsule of duloxetine hydrochloride administered as a single oral dose.

Assessment of the serotonin and norepinephrine reuptake blocking properties of duloxetine in healthy subjects.

Duloxetine is a dual inhibitor of norepinephrine (NE) and serotonin (5-HT) uptake. Initial trials conducted in depressed patients using regimens of 20 mg/day or less did not convincingly demonstrate its efficacy as an antidepressant. The aim of this study was to assess the effects of duloxetine on the 5-HT and NE reuptake processes in healthy human volunteers. Twenty-seven healthy young males without a history of psychiatric disorder were randomly assigned to four groups, each group receiving one of the following daily drug regimens: placebo, clomipramine (a potent 5-HT/NE reuptake blocker) 100 mg/day, duloxetine 20 mg/day, or duloxetine 60 mg/day. In order to assess the NE reuptake process, the pressor response to intravenous tyramine (4 and 6 mg) was measured. Determination of the whole blood 5-HT content was used to evaluate the 5-HT reuptake blockade. These measurements were performed at baseline and repeated after 7 and 14 days of drug intake. Both duloxetine, at doses of 20 to 60 mg/day, and clomipramine significantly interfered with the 5-HT reuptake process, as demonstrated by marked decreases in blood 5-HT concentrations. However, the same doses of duloxetine, unlike clomipramine, failed to impede the usual increase in blood pressure that follows a tyramine intravenous infusion, indicating that clomipramine but not duloxetine blocked NE reuptake. At doses tested in a population of healthy volunteers, duloxetine acted as a selective 5-HT reuptake inhibitor, having no clear effect on the NE reuptake process. Nevertheless, given that the highest dose of duloxetine increased supine systolic blood pressure, it is possible that it represents the threshold regimen for NE reuptake inhibition.

Non-invasive assessment of ocular pharmacokinetics using Confocal Raman Spectroscopy.

A Laser Scanning Confocal Raman Spectroscopy (LSCRS) system was applied for the non-invasive quantification of the transport of a drug through the rabbit cornea in vivo. Employing LSCRS, the changes in the amplitude of a drug-specific Raman signal were assessed over time in the tearfilm and corneal epithelium of the living rabbit eye (n = 6), after topical application of 25 microL Trusopt 2%. This allowed for quantification of pharmacokinetic variables. The effect of the drug on corneal hydration was also monitored. LSCRS demonstrated adequate sensitivity and reproducibility, for continuous real-time monitoring of the Trusopt concentration. Each concentration-time curve had a bi-phasic trend; the rapid initial phase (t<8 min.) corresponds to the nonproductive losses of Trusopt from the tears (k10 = 0.24+/-0.04 min(-1), and the slower later phase (t>20 min.) is the result of transfer of the drug from the corneal epithelium to the stroma (k23 = 0.0047+/-0.0004 min(-1). Drug absorption into the corneal epithelium occurred at a rate of k12 = 0.034+/-0.006 min(-1). Trusopt caused an acute dehydrating effect, with a maximum decrease in corneal hydration of approximately 15% at approximately 60 min. following application of the drug. LSCRS has the specificity, sensitivity, reproducibility and spatial resolution for employment as a potentially valuable tool for the study of ocular pharmacokinetics.