Pharmacokinetics of selective serotonin reuptake inhibitors

Selective serotonin reuptake inhibitors increase sympathetic activity under heavy alcohol exposure in rat models

AIMS

Self-medication with alcohol while being treated with antidepressants is a common problem in patients with depression. Both alcohol consumption and antidepressant administration can induce changes in the cardiac autonomic responses as indicated by heart rate variability (HRV). In this study, we examined cardiac autonomic responses induced by acute heavy alcohol exposure after SSRIs (selective serotonin reuptake inhibitors) medications.

MAIN METHODS

Rats were randomly divided into 3 groups, the alcohol administrated (Alc group), paroxetine administrated (SSRI group), and the SSRI+Alc group. Serum samples were collected to measure blood alcohol concentration (BAC). Physiological and cardiac autonomic responses including mean arterial pressure (MAP), heart rate (HR), and HRV were also compared among groups.

KEY FINDINGS

The SSRI group exhibited higher values of HRV and HF (high frequency) than did the Alc and SSRI+Alc groups after alcohol administration. In contrast to the Alc group, the SSRI+Alc group had significantly lower MAP than Alc group, and higher HR, standard deviation of NN-intervals (SDNN), SDNN to MRR ratio (CVNN), square root of the mean squared differences of the successive NN-intervals (RMSSD) and HF values after alcohol administration.

SIGNIFICANCE

Our results indicate that SSRIs increased sympathetic activity and alcohol reduced it in rats. The present study represents an attractive area for further research.

Intranasal delivery of paroxetine nanoemulsion via the olfactory region for the management of depression: formulation, behavioural and biochemical estimation

Paroxetine is a selective serotonin reuptake inhibitor (SSRI) and is used for the treatment of depression and anxiety problems, but suffers from the drawback of poor oral bioavailability (less than 50%) due to its extensive first pass metabolism. The objective of the present study was to develop a paroxetine loaded nanoemulsion (o/w type) for direct nose-to-brain delivery. Nanoemulsions were prepared by the spontaneous emulsification technique using Capmul MCM, Solutol HS 15 and propylene glycol as oil phase, surfactant and co-surfactant, respectively, for delivery of drug directly to the brain through the nasal route for better management of depression. Formulations were studied for droplet size, polydispersity index (PDI), percentage transmittance, refractive index, viscosity, zeta potential, surface morphology and in vitro permeation study. TEM images of optimized formulation showed spherical droplets with a mean diameter of 58.47 ± 3.02 nm, PDI of 0.339 ± 0.007 and zeta potential values of -33 mV. The formulation showed good results for transmittance (100.60 ± 0.577%), refractive index (1.412 ± 0.003) and viscosity (40.85 ± 6.40 cP). Permeation studies revealed a 2.57-fold enhancement in permeation as compared to the paroxetine suspension. Behavioural studies such as the forced swimming test and locomotor activity test were done on Wistar rats to study the antidepressant effect of the optimized formulation. Treatment of depressed rats with paroxetine nanoemulsion (administered intranasally) significantly improved the behavioural activities in comparison to paroxetine suspension (orally administered). Biochemical estimation results revealed that the prepared nanoemulsion was effective in enhancing the depressed levels of glutathione and decreasing the elevated levels of TBARS.

Stimulation of Sigma-1 Receptor Ameliorates Depressive-like Behaviors in CaMKIV Null Mice

Sigma-1 receptor (Sig-1R) is a molecular chaperone regulating calcium efflux from the neuronal endoplasmic reticulum to the mitochondria. Calcium/calmodulin-dependent protein kinase IV (CaMKIV) null mice exhibit depressive-like behaviors and impaired neurogenesis as assessed by bromodeoxyuridine (BrdU) incorporation into newborn cells of the hippocampal dentate gyrus (DG). Here, we demonstrate that chronic stimulation of Sig-1R by treatment with the agonist SA4503 or the SSRI fluvoxamine for 14 days improves depressive-like behaviors in CaMKIV null mice. By contrast, treatment with paroxetine, which lacks affinity for Sig-1R, did not alter these behaviors. Reduced numbers of BrdU-positive cells and decreased brain-derived neurotrophic factor (BDNF) mRNA expression and protein kinase B (Akt; Ser-473) phosphorylation seen in the DG of CaMKIV null mice were significantly rescued by chronic Sig-1R stimulation. Interestingly, reduced ATP production observed in the DG of CaMKIV null mice was improved by chronic Sig-1R stimulation. Such stimulation also improved hippocampal long-term potentiation (LTP) induction and maintenance, which are impaired in the DG of CaMKIV null mice. LTP rescue was closely associated with both increases in calcium/calmodulin-dependent protein kinase II (CaMKII) autophosphorylation and GluA1 (Ser-831) phosphorylation. Taken together, Sig-1R stimulation by SA4503 or fluvoxamine treatment increased hippocampal neurogenesis, which is closely associated with amelioration of depressive-like behaviors in CaMKIV null mice.

Triple reuptake inhibitors as potential next-generation antidepressants: a new hope?

The current therapy for depression is less than ideal with remission rates of only 25-35% and a slow onset of action with other associated side effects. The persistence of anhedonia originating from depressed dopaminergic activity is one of the most treatment-resistant symptoms of depression. Therefore, it has been hypothesized that triple reuptake inhibitors (TRIs) with potency to block dopamine reuptake in addition to serotonin and norepinephrine transporters should produce higher efficacy. The current review comprehensively describes the development of TRIs and discusses the importance of evaluation of in vivo transporter occupancy of TRIs, which should correlate with efficacy in humans.

Placental transfer of antidepressant medications: implications for postnatal adaptation syndrome

Seven to thirteen percent of women are either prescribed or taking (depending on the study) an antidepressant during pregnancy. Because antidepressants freely cross into the intrauterine environment, we aim to summarize the current findings on placental transfer of antidepressants. Although generally low risk, antidepressants have been associated with postnatal adaptation syndrome (PNAS). Specifically, we explore whether the antidepressants most closely associated with PNAS (paroxetine, fluoxetine, venlafaxine) cross the placenta to a greater extent than other antidepressants. We review research on antidepressants in the context of placental anatomy, placental transport mechanisms, placental metabolism, pharmacokinetics, as well as non-placental maternal and fetal factors. This provides insight into the complexity involved in understanding how placental transfer of antidepressants may relate to adverse perinatal outcomes. Ultimately, from this data there is no pattern in which PNAS is related to placental transfer of antidepressant medications. In general, there is large interindividual variability for each type of antidepressant. To make the most clinically informed decisions about the use of antidepressants in pregnancy, studies that link maternal, placental and fetal genetic polymorphisms, placental transfer rates and infant outcomes are needed.

Prozac affects stickleback nest quality without altering androgen, spiggin or aggression levels during a 21-day breeding test

Pharmaceuticals are increasingly being used in human and veterinary medicine, and their presence in the aquatic environment may present a threat to non-target aquatic organisms. The selective serotonin reuptake inhibitor fluoxetine (Prozac) has been reported to affect diverse behaviours (feeding, aggression, and reproduction) and also the endocrine system (steroid biosynthesis pathway) in fish. To investigate these claims further, and in particular effects on androgen synthesis, male three-spined sticklebacks (Gasterosteus aculeatus) were exposed to fluoxetine at 0, 3.2, 10 and 32μg/L in a flow-through system for 21 days. Their sex was determined prior to exposure using a non-invasive method to collect DNA for determining the genetic sex, reported here for the first time. This was necessary as the exposure required males of a non-breeding status which had not developed secondary characteristics. Post exposure a number of biochemical (serotonin, steroid and spiggin levels) and apical (aggressive behaviour) endpoints were measured. No effects were detected on morphometric parameters, spiggin or androgen (11-ketotestosterone) levels. However, all fluoxetine-exposed male fish had higher cortisol levels in comparison to the control fish, although this effect only persisted throughout the whole exposure duration at the highest concentration (32μg/L). In addition, the ratio of 5-HIAA/5-HT (serotonin metabolite/serotonin) was significantly lower in the brains of males exposed to fluoxetine at all concentrations tested. Although we found no differences in the number of nests built by the males, the quality of the nests produced by the fluoxetine-exposed males was generally inferior consisting only of a basic, rudimentary structure. Males exposed to 32μg/L of fluoxetine displayed a delayed response to a simulated threat (rival male via own mirror image) and were less aggressive (number of bites and attacks) toward their mirror image, but these differences were not statistically significant. In summary, fluoxetine exposure resulted in reduced serotonergic activity in the male three-spined stickleback brain suggesting that the mechanism of action between humans and fish is at least partially conserved. Furthermore, this study provided additional evidence of cross-talk between the serotonergic and stress axes as demonstrated by the perturbations in cortisol levels. This potentially complex interaction at brain level may be responsible for the effects observed on nest quality, an endpoint with serious ecological consequences for this species. Finally, despite our hypothesis (an effect on steroid biosynthesis, based on limited literature evidence), we observed no effects of fluoxetine exposure (at the concentrations and duration employed) on male stickleback androgen levels.

Selective serotonin reuptake inhibitors facilitate ANO6 (TMEM16F) current activation and phosphatidylserine exposure

Anoctamin 6 (ANO6) is a member of the recently identified TMEM16/anoctamin protein family comprising Ca(2+)-activated Cl(-) channels that generate outward-rectifying ionic currents in response to intracellular Ca(2+) increase. ANO6 is also essential for Ca(2+)-dependent phospholipid scrambling required for blood coagulation. Selective serotonin reuptake inhibitors (SSRIs)--fluoxetine, sertraline, and paroxetine-that are used for the treatment of major depressive disorders can increase the risk of upper gastrointestinal bleeding after chronic treatment. However, at the earlier stage of intake, which is 1-7 days after the treatment, the possibility of blood coagulation might also increase, but transiently. Therefore, in this study, we investigated whether therapeutic SSRI concentrations affected the Cl(-) current or phospholipid scrambling activity of ANO6 by assessing ANO6 currents (I ANO6), phosphatidylserine (PS) exposure, and platelet aggregation. In the whole-cell patch mode, SSRIs facilitated Ca(2+)-dependent activation of IANO6 in ANO6-transfected cells, as evidenced by a significant decrease in the delay of IANO6 generation. On the other hand, in the inside-out patch clamp configuration, SSRIs showed an inhibitory effect on ANO6 currents, suggesting that SSRIs activate ANO6 via an indirect mechanism in intact cells. SSRIs also facilitated Ca(2+)-dependent PS exposure and α-thrombin-induced platelet aggregation. These results indicate that SSRIs at clinically relevant concentrations promote Ca(2+)-dependent activation of ANO6, which may have potential clinical implications such as the underlying mechanism of SSRI-induced adverse drug reactions.

Effects of lobeline and reboxetine, fluoxetine, or bupropion combination on depression-like behaviors in mice

Evidence suggests that lobeline, a nicotinic acetylcholine receptor ligand, has antidepressant-like properties in mice. The present study investigated the possible additive or synergistic effects of lobeline in combination with commonly used antidepressants, such as reboxetine, fluoxetine, or bupropion, using the tail suspension test (TST) and the forced swim test (FST) in C57BL/6J mice. Reboxetine (5 or 10 mg/kg, i.p.), fluoxetine (5 or 10 mg/kg, i.p.), or bupropion (2 or 4 mg/kg, i.p.) were administered 30 min before TST or FST. A fixed dose of lobeline (1 mg/kg, i.p.) was injected 15 min prior to tests. Co-administration of lobeline and reboxetine, fluoxetine, or bupropion significantly reduced immobility time in the TST and FST in comparison to the antidepressants used alone. The results suggest that lobeline enhanced the effects of reboxetine, fluoxetine, or bupropion in mice. Therefore, lobeline or similar nicotinic receptor ligand may have therapeutic potential as an adjunct for the treatment of major depression.

New insights into the acute actions from a high dosage of fluoxetine on neuronal and cardiac function: Drosophila, crayfish and rodent models

The commonly used mood altering drug fluoxetine (Prozac) in humans has a low occurrence in reports of harmful effects from overdose; however, individuals with altered metabolism of the drug and accidental overdose have led to critical conditions and even death. We addressed direct actions of high concentrations on synaptic transmission at neuromuscular junctions (NMJs), neural properties, and cardiac function unrelated to fluoxetine's action as a selective 5-HT reuptake inhibitor. There appears to be action in blocking action potentials in crayfish axons, enhanced occurrences of spontaneous synaptic vesicle fusion events in the presynaptic terminals at NMJs of both Drosophila and crayfish. In rodent neurons, cytoplasmic Ca(2+) rises by fluoxetine and is thapsigargin dependent. The Drosophila larval heart showed a dose dependent effect in cardiac arrest. Acute paralytic behavior in crayfish occurred at a systemic concentration of 2mM. A high percentage of death as well as slowed development occurred in Drosophila larvae consuming food containing 100μM fluoxetine. The release of Ca(2+) from the endoplasmic reticulum in neurons and the cardiac tissue as well as blockage of voltage-gated Na(+) channels in neurons could explain the effects on the whole animal as well as the isolated tissues. The use of various animal models in demonstrating the potential mechanisms for the toxic effects with high doses of fluoxetine maybe beneficial for acute treatments in humans. Future studies in determining how fluoxetine is internalized in cells and if there are subtle effects of these mentioned mechanisms presented with chronic therapeutic doses are of general interest.

A population PK model for citalopram and its major metabolite, N-desmethyl citalopram, in rats

A population PK model was developed in order to simultaneously describe citalopram and its major metabolite, n-desmethyl citalopram, plasma concentrations in two different strain of rats after intravenous (IV) and oral (PO) administration of citalopram. Citalopram was administered to Sprague-Dawley (SD) rats at doses: 0.3, 1, 3, and 10 mg/kg IV and 10 mg/kg PO. The compound was dosed orally to Wistar rats at doses: 0.3, 1, 3, 10, 30 and 60 mg/kg. Plasma samples were collected for citalopram and metabolite. Pharmacokinetic analyses were conducted using NONMEM 7.2. Values below the quantification limit (BLQ < 0.1 ng/mL) were included in the analyses and treated as censored information. The disposition of citalopram was best described by a 3-compartment model and its desmethyl metabolite by a 2-compartment model. Several models for the absorption rate were explored (e.g. first, zero order and combined first and zero order absorption, Michaelis-Menten, lag time) in combination with dose and/or time dependent covariate effects. Dose dependent oral bioavailability properties were also identified in this analysis. Citalopram IV clearance and metabolite formation rate were adequately described as linear processes. Metabolite clearance was adequately described using a Michaelis-Menten clearance with different parameters depending on the strain. This analysis demonstrates a very complex absorption/metabolism process explaining the highly non-linear pharmacokinetics observed across all the doses. This is the first combined parent/metabolite population PK analysis in both SD and Wistar rats over a wide range of IV and PO dosages for citalopram, a compound that exhibits highly nonlinear oral pharmacokinetics in rats.

Pharmacokinetic drug-drug interaction study between raltegravir and citalopram

BACKGROUND

Depression is the most common mental health disorder among HIV-infected patients. When treating HIV-infected patients with a selective serotonin reuptake inhibitor (SSRI), potential drug-drug interactions with antiretroviral agents have to be taken into account. We investigated the two-way pharmacokinetic drug-drug interaction and tolerability of concomitant administration of the SSRI citalopram and the HIV-1 integrase inhibitor raltegravir in healthy volunteers.

METHODS

An open-label, crossover, two-period trial was conducted in 24 healthy volunteers. Subjects received the following treatments: citalopram 20 mg once daily for 2 weeks followed by the combination with raltegravir 400 mg twice daily for 5 days and after a washout period raltegravir 400 mg twice daily for 5 days. Intensive steady-state pharmacokinetic blood sampling was performed. Geometric mean ratios (GMRs) of the combination versus the reference treatment and 90% CIs were calculated for the area under the plasma concentration-time curve (AUC). CYP2C19 genotyping was performed because it influences N-demethylation of citalopram to desmethylcitalopram.

RESULTS

A total of 22 healthy volunteers completed the trial. GMRs (90% CI) were 1.00 (0.98, 1.03) for citalopram AUC0-24 h, 0.99 (0.88, 1.12) for desmethylcitalopram AUC0-24 h and 0.77 (0.50, 1.19) for raltegravir AUC0-12 h. Raltegravir plasma concentration 12 h after intake (C12 h) did not change with concomitant use of citalopram. Within each CYP2C19 phenotype subgroup the citalopram metabolite-to-parent ratio, which is a measure for metabolic enzyme activity, was not influenced by concomitant raltegravir use.

CONCLUSIONS

Raltegravir does not influence the pharmacokinetics of citalopram and desmethylcitalopram. Citalopram did not change the pharmacokinetics of raltegravir in a clinically meaningful way. The combination was well tolerated and can be administered without dose adjustments. ClinicalTrials.gov NCT01978782.

The pharmacokinetics of sertraline in overdose and the effect of activated charcoal

AIMS

To investigate the pharmacokinetics (PK) of sertraline in overdose and the effect of single dose activated charcoal (SDAC).

METHODS

Patients presenting to a toxicology unit with sertraline overdoses had demographic and clinical information recorded, and serial serum collected for measurement of sertraline concentrations. Monolix® version 4.2 was used to develop a population PK model of sertraline overdose and the effect of SDAC. Uncertainty in dose time was accounted for by shifting dose time using lag time with between subject variability (BSV). BSV on relative fraction absorbed was used to model uncertainty in dose.

RESULTS

There were 77 timed sertraline concentrations measured in 28 patients with sertraline overdoses with a median dose of 1550 mg (250-5000 mg). SDAC was given to seven patients between 1.5 and 4 h post-overdose. A one compartment model with lag time of 1 h and first order input and elimination adequately described the data. Including BSV on both lag time and relative fraction absorbed improved the model. The population PK parameter estimates for absorption rate constant, volume of distribution and clearance were 0.895 h(-1) , 5340 l and 130 l h(-1) , respectively. The calculated half-life of sertraline following overdose was 28 h (IQR 19.4-30.6h). When given up to 4 h post-overdose, SDAC significantly increased the clearance of sertraline by a factor of 1.9, decreased the area under the curve and decreased the maximum plasma concentration (Cmax ).

CONCLUSIONS

Sertraline had linear kinetics in overdose with parameter values similar to those in therapeutic use. SDAC is effective in increasing clearance when given 1.5 to 4 h post-overdose.

Effects of paroxetine, a CYP2D6 inhibitor, on the pharmacokinetic properties of hydrocodone after coadministration with a single-entity, once-daily, extended-release hydrocodone tablet

PURPOSE

A single-entity, once-daily, extended-release formulation of hydrocodone bitartrate (HYD) has been developed for the management of moderate to severe chronic pain. Hydrocodone undergoes cytochrome P-450 (CYP)-mediated metabolism involving the CYP3A4 and CYP2D6 isozymes. CYP3A4 yields norhydrocodone, a major inactive metabolite, whereas CYP2D6 yields hydromorphone, a minor active metabolite. This study examined the influence of the coadministration of paroxetine, a strong selective CYP2D6 inhibitor, on the pharmacokinetic properties of hydrocodone (and hydromorphone) in healthy adults.

METHODS

In this randomized, double-blind, 2-period, 2-treatment crossover study, 24 healthy subjects received paroxetine 20 mg or placebo once daily for 12 days and an HYD 20-mg tablet on day 10 of each period.

FINDINGS

Hydrocodone mean Cmax and t½ and median Tmax values were similar with paroxetine or placebo coadministration (16.8 vs 15.9 ng/mL, 8.5 vs 8.4 hours, and 18.0 vs 18.0 hours, respectively), as were mean AUC0-t and AUC0-∞ values (342.9 vs 325.3 ng · h/mL and 346.3 vs 328.5 ng · h/mL). The 90% CIs of the geometric mean ratios of the hydrocodone AUC and Cmax values were fully within the predetermined range of 80% to 125%, suggesting that there was no effect of multiple doses of paroxetine on systemic exposure to hydrocodone. Mean hydromorphone AUC0-t and Cmax values were decreased with paroxetine versus placebo (0.64 vs 3.8 ng · h/mL and 0.06 vs 0.19 ng/mL), whereas Tmax values remained similar (18.0 vs 16.1 hours, respectively). The mean hydromorphone AUC0-∞ value could not be calculated. Both regimens were well tolerated; after HYD administration, the numbers of adverse events were similar between the 2 treatment regimens, and all adverse events were mild.

IMPLICATIONS

In this study, the coadministration of single-dose HYD with paroxetine at steady state did not alter systemic exposure to hydrocodone, suggesting that HYD can be coadministered with CYP2D6 inhibitors at therapeutic doses, without dosage modification.

The mechanisms by which antidepressants may reduce coronary heart disease risk

BACKGROUND

Depression is known to increase the risk for coronary heart disease (CHD) likely through various pathogenetic actions. Understanding the links between depression and CHD and the effects of mediating these links may prove beneficial in CHD prevention.

METHODS

An integrated model of CHD was used to elucidate pathogenetic pathways of importance between depression and CHD. Using biomarker relative risk data the pathogenetic effects are representable as measurable effects based on changes in biomarkers.

RESULTS

A 'connection graph' presents interactions by illustrating the relationship between depression and the biomarkers of CHD. The use of selective serotonin reuptake inhibitors (SSRIs) is postulated to have potential to decrease CHD risk. Comparing the 'connection graph' of SSRI's to that of depression elucidates the possible actions through which risk reduction may occur.

CONCLUSIONS

The CHD effects of depression appear to be driven by increased inflammation and altered metabolism. These effects might be mediated with the use of SSRI's.

Pharmacokinetics of antidepressants in patients with hepatic impairment

Appropriate use of antidepressant in patients with hepatic impairment requires careful consideration of how the hepatic illness may affect pharmacokinetics. This review aims to analyze pharmacokinetic profile, plasma level variations so as the metabolism of several antidepressants relating to their use in patients with an hepatic impairment. Due to the lack of data regarding hepatic impairment itself, the review is focused mainly on studies investigating pharmacokinetics in hepatic cirrhosis or alcohol-related conditions. More data on reduced hepatic metabolism can be extrapolated by drug studies conducted in elderly populations. Dose adjustment of antidepressants in these patients is important as most of these drugs are predominantly metabolized by the liver and many of them are associated with dose-dependent adverse reactions. As no surrogate parameter is available to predict hepatic metabolism of drugs, dose adjustment according to pharmacokinetic properties of the drugs is proposed. There is a need for a more balanced assessment of the benefits and risks associated with antidepressants use in patients with hepatic impairment, particularly considering pharmacokinetic profile of the drugs to ensure that patients, who would truly benefit from these agents, are not denied appropriate treatment. In conclusion, kinetic studies for centrally acting drugs including antidepressants with predominant hepatic metabolism should be carried out in patients with liver disease to allow precise dose recommendations for enhanced patient safety.

Exploring the role of drug-metabolising enzymes in antidepressant side effects

RATIONALE

Cytochrome P450 enzymes are important in the metabolism of antidepressants. The highly polymorphic nature of these enzymes has been linked to variability in antidepressant metabolism rates, leading to hope regarding the use of P450 genotyping to guide treatment. However, evidence that P450 genotypic differences underlie the variation in treatment outcomes is inconclusive.

OBJECTIVES

We explored the links between both P450 genotype and serum concentrations of antidepressant with antidepressant side effects, using data from the Genome-Based Therapeutic Drugs for Depression Project (GENDEP), which is a large (n = 868), pharmacogenetic study of depressed individuals treated with escitalopram or nortriptyline.

METHODS

Patients were genotyped for the enzymes CYP2C19 and CYP2D6, and serum concentrations of both antidepressant and primary metabolite were measured after 8 weeks of treatment. Side effects were assessed weekly. We investigated associations between P450 genotypes, serum concentrations of antidepressants and side effects, as well as the relationship between P450 genotype and study discontinuation.

RESULTS

P450 genotype did not predict total side effect burden (nortriptyline: n = 251, p = 0.5638, β = -0.133, standard error (SE) = 0.229; escitalopram: n = 340, p = 0.9627, β = -0.004, SE = 0.085), study discontinuation (nortriptyline n = 284, hazard ratio (HR) = 1.300, p = 0.174; escitalopram n = 376, HR = 0.870, p = 0.118) or specific side effects. Serum concentrations of antidepressant were only related to a minority of the specific side effects measured: dry mouth, dizziness and diarrhoea.

CONCLUSIONS

In this sample where antidepressant dosage is titrated using clinical judgement, P450 genotypes do not explain differences between patients in side effects with antidepressants. Serum drug concentrations appear to only explain variability in the occurrence of a minority of specific side effects.

Effect of Cytochrome P450 polymorphism on the action and metabolism of selective serotonin reuptake inhibitors

INTRODUCTION

The aim of this article is to review the field of clinically relevant pharmacogenetic effects of cytochrome P450 polymorphisms on metabolism, kinetics, and action of selective serotonin reuptake inhibitors (SSRIs).

AREAS COVERED

The relevant literature in humans on the implications of genetic variation on SSRI drug exposure, drug safety, and efficacy was systematically evaluated. There is a large amount of evidence on the influences of CYP polymorphisms on the pharmacokinetics of SSRIs. Regulatory agencies have issued warnings or advice considering dose adjustments in the presence of affected metabolic phenotypes for several SSRIs. Evidence-based dose adjustments for drugs dependent on CYP genotype are available to clinicians. However, few data on the relationship between genetically determined elevated plasma concentrations of SSRIs and specific side effects or therapeutic failure are currently available.

EXPERT OPINION

Genetic polymorphisms in CYP2D6 and CYP2C19 exert large influences on the individual exposure to SSRIs, leading to the aim to achieve similar concentration time courses in different metabolizer phenotypes. The implementation of a stratified approach to medication with SSRIs in different metabolic phenotypes on a rational basis will require new studies assessing the association between clinical outcomes (such as adverse reactions) and genetically determined elevated plasma concentrations.

Pharmaceuticals and personal care products: A critical review of the impacts on fish reproduction

Research in environmental toxicology involving pharmaceuticals and personal care products (PPCPs) has increased greatly over the last 10-15 years. Much research has been focused on the endocrine-disrupting potential of PPCPs, as they relate to negative population impacts of aquatic organisms. This review assesses the current data on the reported effects of PPCPs on fish reproduction with an emphasis on fecundity, a predictor of population effects. Studies of both individual PPCPs and PPCP mixtures are presented. As the majority of individual PPCP studies reviewed demonstrate negative effects on fish fecundity, we relate these findings to detected surface water concentrations of these compounds. Very few studies involving PPCP mixtures have been conducted; however, the need for these types of studies is warranted as fish are most likely exposed to mixtures of PPCPs in the wild. In addition, laboratory and field assessments of wastewater treatment plant (WWTP) effluents, a major source of PPCPs, are reviewed. Much of the data provided from these assessments are variable and do not generally demonstrate negative impacts on reproduction, or the studies are unable to directly associate observed effects with WWTP effluents. Finally, future research considerations are outlined to provide an avenue into understanding how wild populations of fish are affected by PPCPs. These considerations are aimed at determining the adaptation potential of fish exposed to mixtures of PPCPs over multiple generations. As global use of PPCPs continually rises, the need to discern the effects of chronic exposure to PPCPs is greatly increased.

The role of 5-HT1A receptors in mediating acute negative effects of antidepressants: implications in pediatric depression

Acute antidepressant exposure elevates the frequency of impulsive behavior and suicidal thoughts in children and adolescents with major depressive disorder (MDD). Long-term antidepressant treatment, however, is beneficial for pediatric MDD, so it is necessary to explore novel treatments that prevent the potentially dangerous consequences of acute antidepressant initiation. In the present study, a treatment strategy designed to reverse the acute negative behavioral effects of antidepressants was tested in rodents. Co-administration of the 5-HT1A receptor (5-HT1AR) antagonist WAY-100635 reversed the negative effects of acute fluoxetine, a serotonin reuptake inhibitor, but not reboxetine, a norepinephrine reuptake inhibitor, supporting the involvement of 5-HT1AR in mediating the negative consequences of acute selective serotonin reuptake inhibitor (SSRI) treatment. No 5-HT1AR antagonists are currently approved for use in pediatric populations, so alternative strategies should be explored. One such strategy was suggested based on the hypothesis that the rate of 5-HT1AR activation and the subsequent inhibition of serotonergic neuron activity caused by acute SSRI administration is proportional to the loading rate of an antidepressant. Existing pharmacological data were examined, and significant correlations were observed between the half-life of antidepressants and the rate of suicide-related events (SREs). Specifically, antidepressants with longer half-lives have lower rates of SREs. On the basis of these data, novel dosing strategies were developed for five antidepressants to mimic the pharmacological profile of the antidepressant with the longest half-life, fluoxetine. These dosing strategies could be used to decrease the rate of SREs associated with acute antidepressant treatment in pediatric MDD until an improved pharmacological treatment is developed.

Chronic effects of 17α-ethinylestradiol, fluoxetine, and the mixture on individual and population-level end points in Daphnia magna

Many pharmaceuticals and personal care products (PPCPs) enter the environment continuously. Because these chemicals are not intended for environmental applications, testing for environmental effects is not mandatory, and thus relatively little is known about their ecological effects, particularly on invertebrate species. To better understand the effects of PPCPs on freshwater invertebrates, we exposed the water flea Daphnia magna to environmentally relevant concentrations of the pharmaceuticals 17α-ethinylestradiol (EE2) and fluoxetine both individually and as a mixture for 40 days. Exposure to EE2 decreased the number of neonates produced per female at 0.1 and 1.0 µg/L EE2, whereas fluoxetine increased mortality and neonate production at 100 µg/L. Exposure to the mixture of EE2 + fluoxetine increased time to first reproduction in medium and high mixture treatments and decreased time to death and neonate production in the high mixture treatment. When these individual parameters were integrated into a demographic model, population growth rate decreased when D. magna were exposed to 0.1 and 1.0 µg/L EE2, 100 µg/L fluoxetine, and low and high mixture treatments. When we compared the results of our extended 40 day exposures with data from only the first 21 days, the standard duration of chronic toxicity tests with D. magna, the effects of pharmaceutical exposure were generally significant at lower chemical concentrations during the 21-day period compared with the 40-day exposures, which points to the importance of exposure duration in drawing inferences from toxicity studies.

Orexin neuropeptides contribute to the development and persistence of generalized avoidance behavior in the rat

RATIONALE

Avoidance of contexts directly associated with fearful experiences represents an adaptive behavioral survival strategy. Over-interpretation of contextual cues leading to generalized avoidance of situations that are only remotely similar to the original fear context represents a pathologic process that contributes to anxiety disorders. Orexin neuropeptides modulate anxiety-like behavioral and physiological responses.

OBJECTIVE

The objective of this paper was to investigate the impact of pharmacological orexin receptor blockade on generalized avoidance behavior.

METHODS

Rats received a single electric foot-shock in the dark side of a two-compartment shuttle box followed by situational context reminders. After shock, rats were treated chronically (3 weeks) with the orexin receptor antagonist almorexant or with the selective serotonin reuptake inhibitor sertraline, used as positive anxiolytic control. In week 3, avoidance behavior was measured under conditions of high (dark-light (DL)-box) and low (elevated plus maze (EPM)) similarity to the original shock context. Avoidance behavior was re-assessed 5 and 17 weeks after treatment termination.

RESULTS

Avoidance in the DL box (contextual fear memory) remained unaffected by any treatment and lasted 20 weeks post-shock exposure. Avoidance in the EPM (neophobic fear generalization) was partially attenuated during treatment with almorexant and sertraline at week 3. Following 5 and 17 weeks of drug washout, avoidance in the EPM was significantly reduced in almorexant- but not in sertraline-treated rats. Almorexant also reduced persistent avoidance in the EPM upon treatment initiation 3 weeks after shock exposure.

CONCLUSION

Chronic orexin receptor blockade in rats reduces both the development and persistence of generalized avoidance in situations with low similarity to the initial shock context.

Development and application of the adverse outcome pathway framework for understanding and predicting chronic toxicity: II. A focus on growth impairment in fish

Adverse outcome pathways (AOPs) organize knowledge on the progression of toxicity through levels of biological organization. By determining the linkages between toxicity events at different levels, AOPs lay the foundation for mechanism-based alternative testing approaches to hazard assessment. Here, we focus on growth impairment in fish to illustrate the initial stages in the process of AOP development for chronic toxicity outcomes. Growth is an apical endpoint commonly assessed in chronic toxicity tests for which a replacement is desirable. Based on several criteria, we identified reduction in food intake to be a suitable key event for initiation of middle-out AOP development. To start exploring the upstream and downstream links of this key event, we developed three AOP case studies, for pyrethroids, selective serotonin reuptake inhibitors (SSRIs) and cadmium. Our analysis showed that the effect of pyrethroids and SSRIs on food intake is strongly linked to growth impairment, while cadmium causes a reduction in growth due to increased metabolic demands rather than changes in food intake. Locomotion impairment by pyrethroids is strongly linked to their effects on food intake and growth, while for SSRIs their direct influence on appetite may play a more important role. We further discuss which alternative tests could be used to inform on the predictive key events identified in the case studies. In conclusion, our work demonstrates how the AOP concept can be used in practice to assess critically the knowledge available for specific chronic toxicity cases and to identify existing knowledge gaps and potential alternative tests.

Tramadol for premature ejaculation: a systematic review and meta-analysis

BACKGROUND

Tramadol is a centrally acting analgesic prescribed off-label for the treatment of premature ejaculation (PE). However, tramadol may cause addiction and difficulty in breathing and the beneficial effect of tramadol in PE is yet not supported by a high level of evidence. The purpose of this study was to systematically review the evidence from randomised controlled trials (RCT) for tramadol in the management of PE.

METHODS

We searched bibliographic databases including MEDLINE to August 2014 for RCTs. The primary outcome was intra-vaginal ejaculatory latency time (IELT). Methodological quality of RCTs was assessed. Between-group differences in IELT and other outcomes were pooled across RCTs in a meta-analysis. Statistical and clinical between-trial heterogeneity was assessed.

RESULTS

A total of eight RCTs that evaluated tramadol against a comparator were included. The majority of RCTs were of unclear methodological quality due to limited reporting. Pooled evidence (four RCTs, 721 participants), suggests that tramadol is significantly more effective than placebo at increasing IELT over eight to 12 weeks (p = 0.0007). However, a high level of statistical heterogeneity is evident (I-squared = 74%). Single RCT evidence indicates that tramadol is significantly more effective than paroxetine taken on-demand, sildenafil, lidocaine gel, or behavioural therapy on IELT in men with PE. Tramadol is associated with significantly more adverse events including: erectile dysfunction, constipation, nausea, headache, somnolence, dry mouth, dizziness, pruritus, and vomiting, than placebo or behavioural therapy over eight to 12 weeks of treatment. However, addiction problems or breathing difficulties reported by patients for PE is not assessed in the current evidence base.

CONCLUSIONS

Tramadol appears effective in the treatment of PE. However, these findings should be interpreted with caution given the observed levels of between-trial heterogeneity and the reporting quality of the available evidence. The variability across placebo-controlled trials in terms of the tramadol dose evaluated and the treatment duration does not permit any assessment of a safe and effective minimum daily dose. The long-term effects and side effects, including addiction potential, for men with PE have not been evaluated in the current evidence base.

TRIAL REGISTRATION

The review is registered on PROSPERO 2013: CRD42013005289 .

Effects of the antidepressant fluoxetine in spiked-sediments on developmental and reproductive features of the polychaetes Capitella teleta and Capitella sp A

The cosmopolitan species-complex Capitella, a deposit-feeding polychaete, is widely used as an indicator of organic pollution and plays an important role in sewage waste cycling in marine and estuarine ecosystems. The antidepressant fluoxetine can be accumulated in sewage effluents and it could pose a hazard to infauna inhabiting surrounding areas. The study aimed to assess effects of fluoxetine on juveniles and adults of Capitella teleta and Capitella sp A. Sediments were spiked with four fluoxetine concentrations (0.001, 0.03, 0.3 and 3.3 µg/g dry wt. sediment). Chronically exposed worms of C. teleta showed delay of maturity, delay or inhibition of copulation and morphological abnormalities (genital spines in males and juveniles) with adverse physiological consequences. Alternatively, in C. teleta fluoxetine enhanced proteroginous individuals that may be beneficial for the population. Worms of Capitella sp A only showed delay or inhibition of copulation. Observed fluoxetine adverse effects could have important ecological implications in natural populations of aquatic invertebrates due to the possible alteration or even inhibition of reproductive processes.

Environmentally relevant concentrations of citalopram partially inhibit feeding in the three-spine stickleback (Gasterosteus aculeatus)

Selective Serotonin Re-uptake Inhibitors (SSRI) are mood-altering, psychotropic drugs commonly used in the treatment of depression and other psychological illnesses. Many of them are poorly degraded in sewage treatment plants and enter the environment unaltered. In laboratory studies, they have been demonstrated to affect a wide range of behaviours in aquatic organisms. In this study we investigated the effect of a three-week exposure to 0.15 and 1.5 μg/l of the SSRI citalopram dissolved in the ambient water on the feeding behaviour in three-spine stickleback (Gasterosteus aculeatus). Feeding, measured as the number of attacks performed on a piece of frozen bloodworms during a 10-min period, was reduced by 30-40% in fish exposed to both 0.15 and 1.5 μg/l citalopram. The effects of the environmentally relevant concentration 0.15 μg/l on feeding, an important fitness characteristic, suggests that the ecological significance of environmental SSRI exposure may be pronounced.

Occurrence of venlafaxine, other antidepressants and selected metabolites in the Rhine catchment in the face of climate change

Fate and occurrence of 4 selective serotonin reuptake inhibitors, one serotonin-noradrenergic reuptake inhibitor and one noradrenergic-dopamineric reuptake inhibitor and their human metabolites were determined in a German municipal wastewater treatment plant as well as in the Rhine River and selected tributaries. The enantiomeric fractions of venlafaxine and its metabolites were not altered during wastewater treatment and were similar in all river samples underlining that no appreciable biodegradation occurs. In the Rhine catchment area highest concentrations were detected for venlafaxine, citalopram and their human metabolites. Projected future climate change would lead to an increased portion of treated wastewater in rivers due to reduced discharges during low flow situations by the end of the 21st century. However, the effect of climate change on the pattern and concentrations of antidepressants is predicted to be of minor importance in comparison to altered consumption quantities caused by demographic developments and changes in life styles.

Elevation of brain allopregnanolone rather than 5-HT release by short term, low dose fluoxetine treatment prevents the estrous cycle-linked increase in stress sensitivity in female rats

Withdrawal from long-term dosing with exogenous progesterone precipitates increased anxiety-linked changes in behavior in animal models due to the abrupt decrease in brain concentration of allopregnanolone (ALLO), a neuroactive metabolite of progesterone. We show that a withdrawal-like effect also occurs during the late diestrus phase (LD) of the natural ovarian cycle in rats, when plasma progesterone and ALLO are declining but estrogen secretion maintains a stable low level. This effect at LD was prevented by short-term treatment with low dose fluoxetine. During LD, but not at other stages of the estrous cycle, exposure to anxiogenic stress induced by whole body vibration at 4 Hz for 5 min evoked a significant decrease in tail flick latency (stress-induced hyperalgesia) and a decrease in the number of Fos-positive neurons present in the periaqueductal gray (PAG). The threshold to evoke fear-like behaviors in response to electrical stimulation of the dorsal PAG was lower in the LD phase, indicating an increase in the intrinsic excitability of the PAG circuitry. All these effects were blocked by short-term administration of fluoxetine (2 × 1.75 mg kg(-1) i.p.) during LD. This dosage increased the whole brain concentration of ALLO, as determined using gas chromatography-mass spectrometry, but was without effect on the extracellular concentration of 5-HT in the dorsal PAG, as measured by microdialysis. We suggest that fluoxetine-induced rise in brain ALLO concentration during LD offsets the sharp physiological decline, thus removing the trigger for the development of anxiogenic withdrawal effects.

Development of potent dopamine-norepinephrine uptake inhibitors (DNRIs) based on a (2S,4R,5R)-2-benzhydryl-5-((4-methoxybenzyl)amino)tetrahydro-2H-pyran-4-ol molecular template

Current therapy of depression is less than ideal with remission rates of only 25-35% and response rates of 45-60%. It has been hypothesized that a dysfunctional dopaminergic system in the mesocorticolimbic pathway in depressive disorder may lead to development of anhedonia associated with loss of pleasure and interest along with loss of motivation. The current antidepressants do not address dopamine dysfunction which might explain their low efficacy. In this report, we have described an SAR study on our pyran-based triple reuptake inhibitors (TRIs) which are being investigated as the next-generation antidepressants. In the present work we demonstrate that our lead TRIs can be modified with appropriate aromatic substitutions to display a highly potent SSRI profile for compounds 2a and 4a (Ki (SERT); 0.71 and 2.68nM, respectively) or a potent DNRI profile for compounds 6b and 6h (Ki (DAT/NET); 8.94/4.76 and 13/7.37nM, respectively). Compounds 4g-4i exhibited potencies at all three monoamine transporters. The results provide insights into the structural requirements for developing selective dual- and triple-uptake inhibitors from a unique pyran molecular template for an effective management of depression and related disorders.

(S)-citalopram influences amygdala modulation in healthy subjects: a randomized placebo-controlled double-blind fMRI study using dynamic causal modeling

Citalopram and Escitalopram are gold standard pharmaceutical treatment options for affective, anxiety, and other psychiatric disorders. However, their neurophysiologic function on cortico-limbic circuits is incompletely characterized. Here we studied the neuropharmacological influence of Citalopram and Escitalopram on cortico-limbic regulatory processes by assessing the effective connectivity between orbitofrontal cortex (OFC) and amygdala using dynamic causal modeling (DCM) applied to functional MRI data. We investigated a cohort of 15 healthy subjects in a randomized, crossover, double-blind design after 10days of Escitalopram (10mg/d (S)-citalopram), Citalopram (10mg/d (S)-citalopram and 10mg/d (R)-citalopram), or placebo. Subjects performed an emotional face discrimination task, while undergoing functional magnetic resonance imaging (fMRI) scanning at 3 Tesla. As hypothesized, the OFC, in the context of the emotional face discrimination task, exhibited a down-regulatory effect on amygdala activation. This modulatory effect was significantly increased by (S)-citalopram, but not (R)-citalopram. For the first time, this study shows that (1) the differential effects of the two enantiomers (S)- and (R)-citalopram on cortico-limbic connections can be demonstrated by modeling effective connectivity methods, and (2) one of their mechanisms can be linked to an increased inhibition of amygdala activation by the orbitofrontal cortex.

The importance of glia in dealing with stress

Glia are starting to be accepted as the equal of neurons. Their impact on intelligence, environmental enrichment, and cerebral dominance forms the basis for understanding the role of glia in stress. Along with neurons, astrocytes, microglia, NG2 cells, and oligodendrocytes all contribute. Glia can even be protective against drug abuse. Glial effects on depression, mood disorders and schizophrenia are reviewed.

Quantitative cross-species extrapolation between humans and fish: the case of the anti-depressant fluoxetine

Fish are an important model for the pharmacological and toxicological characterization of human pharmaceuticals in drug discovery, drug safety assessment and environmental toxicology. However, do fish respond to pharmaceuticals as humans do? To address this question, we provide a novel quantitative cross-species extrapolation approach (qCSE) based on the hypothesis that similar plasma concentrations of pharmaceuticals cause comparable target-mediated effects in both humans and fish at similar level of biological organization (Read-Across Hypothesis). To validate this hypothesis, the behavioural effects of the anti-depressant drug fluoxetine on the fish model fathead minnow (Pimephales promelas) were used as test case. Fish were exposed for 28 days to a range of measured water concentrations of fluoxetine (0.1, 1.0, 8.0, 16, 32, 64 µg/L) to produce plasma concentrations below, equal and above the range of Human Therapeutic Plasma Concentrations (H_TPCs). Fluoxetine and its metabolite, norfluoxetine, were quantified in the plasma of individual fish and linked to behavioural anxiety-related endpoints. The minimum drug plasma concentrations that elicited anxiolytic responses in fish were above the upper value of the H_TPC range, whereas no effects were observed at plasma concentrations below the H_TPCs. In vivo metabolism of fluoxetine in humans and fish was similar, and displayed bi-phasic concentration-dependent kinetics driven by the auto-inhibitory dynamics and saturation of the enzymes that convert fluoxetine into norfluoxetine. The sensitivity of fish to fluoxetine was not so dissimilar from that of patients affected by general anxiety disorders. These results represent the first direct evidence of measured internal dose response effect of a pharmaceutical in fish, hence validating the Read-Across hypothesis applied to fluoxetine. Overall, this study demonstrates that the qCSE approach, anchored to internal drug concentrations, is a powerful tool to guide the assessment of the sensitivity of fish to pharmaceuticals, and strengthens the translational power of the cross-species extrapolation.

Fluoxetine: juvenile pharmacokinetics in a nonhuman primate model

RATIONALE

The selective serotonin reuptake inhibitor (SSRI) fluoxetine is the only psychopharmacological agent approved for use in children. While short-term studies of side effects have been performed, long-term consequences for brain development are not known. Such studies can be performed in appropriate animal models if doses modeling therapeutic use in children are known.

OBJECTIVES

The goal of this study was to identify a daily dose of fluoxetine in juvenile monkeys which would result in serum fluoxetine and norfluoxetine concentrations in the therapeutic range for children.

METHODS

Juvenile (2.5-year-old rhesus monkeys, n = 6) received single administration of doses of 1, 2, and 4 mg/kg day fluoxetine on a background of chronic dosing at an intermediate level to provide steady-state conditions to model therapeutic administration. Using nonlinear modeling, standard pharmacokinetic parameters were derived. Cerebrospinal fluid monoamine neurotransmitters were assayed to confirm the pharmacological effects.

RESULTS

Dose-dependent area under the curve (AUC) and C max values were seen, while T max and absorption/elimination half-lives were minimally influenced by dose. A dosage of 2 mg/kg day given over a 14-week period led to steady-state serum concentrations of active agent (fluoxetine + norfluoxetine) similar to those recorded from drug monitoring studies in children. Cisternal cerebrospinal fluid concentrations of serotonin increased significantly over the 14-week period, while concentrations of the serotonin metabolite (5-HIAA) were lower but not significantly different.

CONCLUSIONS

A dose of 2 mg/kg day fluoxetine in juvenile rhesus monkeys provides an internal dose similar to therapeutic use in children and will help establish a valuable animal model for understanding fluoxetine's therapeutic and potential adverse effects in children.

Effect of the potent CYP2D6 inhibitor sarpogrelate on the pharmacokinetics and pharmacodynamics of metoprolol in healthy male Korean volunteers

1. Recently, we demonstrated that sarpogrelate is a potent and selective CYP2D6 inhibitor in vitro. Here, we evaluated the effect of sarpogrelate on the pharmacokinetics and pharmacodynamics of metoprolol in healthy subjects. 2. Nine healthy male subjects genotyped for CYP2D6*1/*1 or *1/*2 were included in an open-label, randomized, three treatment-period and crossover study. A single oral dose of metoprolol (100 mg) was administered with water (treatment A) and sarpogrelate (100 mg bid.; a total dose of 200 mg and treatment B), or after pretreatment of sarpogrelate for three days (100 mg tid.; treatment C). Plasma levels of metoprolol and α-hydroxymetoprolol were determined using a validated LC-MS/MS method. Changes in heart rate and blood pressure were monitored as pharmacodynamic responses to metoprolol. 3. Metoprolol was well tolerated in the three treatment groups. In treatment B and C groups, the AUCt of metoprolol increased by 53% (GMR, 1.53; 90% CI, 1.17-2.31) and by 51% (1.51; 1.17-2.31), respectively. Similar patterns were observed for the increase in Cmax of metoprolol by sarpogrelate. However, the pharmacodynamics of metoprolol did not differ significantly among the three treatment groups. 4. Greater systemic exposure to metoprolol after co-administration or pretreatment with sarpogrelate did not result in clinically relevant effects. Co-administration of both agents is well tolerated and can be employed without the need for dose adjustments.

Enantioselective biodegradation of fluoxetine by the bacterial strain Labrys portucalensis F11

Fluoxetine (FLX) is a chiral fluorinated pharmaceutical indicated mainly for the treatment of depression and is one of the most dispensed drugs in the world. There is clear evidence of environmental contamination with this drug and its active metabolite norfluoxetine (NFLX). In this study the enantioselective biodegradation of racemic FLX and of its enantiomers by Labrys portucalensis strain F11 was assessed. When 2μM of racemic FLX was supplemented as sole carbon source, complete removal of both enantiomers, with stoichiometric liberation of fluoride, was achieved in 30d. For racemic FLX concentration of 4 and 9μM, partial degradation of the enantiomers was obtained. In the presence of acetate as an additional carbon source, at 4, 9 and 21μM of racemic FLX and at 25μM of racemic FLX, (S)-FLX or (R)-FLX, complete degradation of the two enantiomers occurred. At higher concentrations of 45 and 89μM of racemic FLX, partial degradation was achieved. Preferential degradation of the (R)-enantiomer was observed in all experiments. To our knowledge, this is the first time that enantioselective biodegradation of FLX by a single bacterium is reported.

Total synthesis of fluoxetine and duloxetine through an in situ imine formation/borylation/transimination and reduction approach

We report efficient, catalytic, asymmetric total syntheses of both (R)-fluoxetine and (S)-duloxetine from α,β-unsaturated aldehydes conducting five sequential one-pot steps (imine formation/copper mediated β-borylation/transimination/reduction/oxidation) followed by the specific ether group formation which deliver the desired products (R)-fluoxetine in 45% yield (96% ee) and (S)-duloxetine in 47% yield (94% ee).

Pharmacotherapy for disorders of consciousness: are 'awakening' drugs really a possibility?

Disorders of consciousness, including the coma state, vegetative state and minimally conscious state, are among the least understood and least curable conditions in modern neurology. Structural or functional injuries may produce impairments in the neuronal circuits (the ascending reticular activating system and thalamocortical loops) responsible for maintaining the wakefulness state and awareness, associated with a change in neurotransmitter concentrations. Pharmacological agents that are able to restore the levels of neurotransmitters and, consequently, neural synaptic plasticity and functional connectivity of consciousness networks, may play an important role as drugs useful in improving the consciousness state. Currently, there is growing interest in the scientific community with regard to pharmacological agents that act on the gamma amino-butyric acid (GABA) system, such as zolpidem and baclofen, and monoamine systems, such as dopaminergic agents and some antidepressants. The purpose of this article is to provide a comprehensive overview of these potential 'awakening' drugs in patients with disorders of consciousness. The possible mechanisms by which these drugs may exert their effects in promoting recovery of consciousness are discussed, highlighting how many findings are often the result of sporadic events rather than prospective controlled trials or implementation of standard treatment guidelines.

Tissue-specific bioconcentration of antidepressants in fish exposed to effluent from a municipal sewage treatment plant

Tissue-specific bioconcentration of selected antidepressants was studied in rainbow trout (Oncorhynchus mykiss) exposed to undiluted effluent from a Swedish municipal sewage treatment plant for 13 days. Citalopram, sertraline and venlafaxine were found in the brains and livers of most fish, but not in blood plasma or muscle. Venlafaxine was the only drug found in plasma (3/20 fish). Fluoxetine was not detected in any fish tissue, in accordance with a low concentration in the effluent and a comparably high limit of quantification in tissues. Concentrations of citalopram, sertraline and venlafaxine in fish brain were up to 1/12, 1/8 and 1/26, respectively, of the lowest concentrations found in the brains of mammals treated with therapeutic doses. Thus, given co-exposure to several antidepressants and an assumed similar potency in fish, the margin of safety for target-related effects in fish residing in effluent-dominated streams is relatively low. Furthermore, the non-detectable levels of these drugs in blood plasma suggest that analyses of concentrations in target tissues (brain) would be more informative in field studies and other studies with environmentally realistic exposure concentrations.

Assessment of cytotoxic and immunomodulatory properties of four antidepressants on primary cultures of abalone hemocytes (Haliotis tuberculata)

Pharmaceutical compounds like antidepressants found in surface waters raise concerns due to their potential toxicity on non-target aquatic organisms. This study aimed at investigating the in vitro cytotoxicity and immunomodulatory properties of four common antidepressants, namely Amitriptyline, Clomipramine, Citalopram and Paroxetine, on primary cultures of abalone hemocytes (Haliotis tuberculata), after 48 h-exposure. Effects on immunocompetence (phagocytosis, levels of reactive oxygen species, esterase activity and lysosomal membrane destabilization) were assessed. Results obtained by MTT assays revealed that acute toxicity is unlikely to occur in the environment since the LC50s of the four antidepressants are at the mg/L level. The different immunological endpoints displayed a biphasic response, with an increase at the lowest concentration (i.e. 1 μg/L) followed by a decrease at higher concentrations. Overall, Amitriptyline and Clomipramine, the two tricyclic antidepressants, had higher immunomodulatory capacities than the two selective serotonin reuptake inhibitors Citalopram and Paroxetine. Amitriptyline was the most potent and Citalopram the least potent drug in altering immune function in H. tuberculata.

A comparative review of escitalopram, paroxetine, and sertraline: Are they all alike?

It is known that newer antidepressants, such as the selective serotonin reuptake inhibitors (SSRIs), provide advantages in tolerability over antidepressants such as the tricyclics. However, even within the SSRI class, differences in efficacy or tolerability exist between the individual drugs. Among the three most widely prescribed SSRIs are paroxetine, sertraline, and escitalopram. Escitalopram is commonly referred to as an SSRI, but also has well-documented allosteric properties, and thus can be further classed as an allosteric serotonin reuptake inhibitor. All three antidepressants are efficacious compared with placebo, but there is evidence that escitalopram is more effective than a range of other antidepressants. There are no direct data to regard either paroxetine or sertraline as a superior antidepressant. Escitalopram is superior compared with paroxetine, which has a less favorable tolerability profile. Paroxetine is associated with cholinergic muscarinic antagonism and potent inhibition of CYP2D6, and sertraline has moderate drug interaction issues in comparison with escitalopram. Overall, as an allosteric serotonin reuptake inhibitor that is somewhat different from classical SSRIs, escitalopram is the first choice judged by combined efficacy and tolerability, and nonclinical data have offered possible mechanisms through which escitalopram could be more efficacious, based on its interaction with orthosteric and allosteric binding sites at the serotonin transporter.

Drug safety evaluation of olanzapine/fluoxetine combination

INTRODUCTION

Bipolar disorder and treatment-resistant depression (TRD) are common and recurrent conditions associated with significant disability, morbidity and mortality. Despite the clear need for effective treatments, only a few medications have been approved in the US for these indications. The combined formulation of olanzapine-fluoxetine (OFC) has been available for a decade now, thus a review on its safety profile and comparative efficacy is timely and can help clinicians to determine the benefit/risk profile of OFC within the context of other treatment alternatives.

AREAS COVERED

This paper summarizes the rationale and evidence supporting the use of OFC for both bipolar I depressive episodes and TRD with a focus on safety and tolerability. Product labels and the search engine PubMed was used to obtain relevant information on this subject.

EXPERT OPINION

Although further comparative studies are needed, the literature confirms that the OFC is an effective treatment for bipolar I depressive episodes, as well as major depressive episodes that have not responded to several adequate courses of antidepressant therapy. Its use as a first-line treatment for bipolar I depressive episodes and at a higher rung of algorithms for patients with TRD is limited by its propensity to cause weight gain and associated metabolic symptoms.

Occurrence of antidepressant residues in the sewage-impacted Vistula and Utrata rivers and in tap water in Warsaw (Poland)

Antidepressants, even at low concentrations, can reveal some adverse effects on aquatic life due to disturbing homeostasis throughout the central and peripheral nervous system both in vertebrates and invertebrates. To date there have not been any reports regarding the presence of these pharmaceuticals in surface and tap waters in Eastern Europe. Therefore the aim of this study was to determine the presence of 21 antidepressant pharmaceuticals at specific points of the main Polish river - the Vistula, a smaller river of the Warsaw region - the Utrata, as well as in tap water samples of Warsaw. Samples were collected twice at one month intervals and analysed using solid-phase extraction (SPE) technique coupled with the liquid chromatography-electrospray ionisation-tandem mass spectrometer (LC-MS/MS) method operated under the multiple reaction monitoring mode (MRM). This is the first study where active compounds such as moclobemid or trazodone in the environment have been investigated. Environmental risk assessment of antidepressants in Poland was estimated on the basis of annuals sale data extracted from the NFZ (Narodowy Fundusz Zdrowia-National Health Service) base of reimbursed pharmaceuticals(1). Predicted environmental concentration (PEC) of target pharmaceuticals were compared with their measured concentration (MEC). Moreover, the application of the EMEA/CHMP guideline for environmental risk assessment of the antidepressants was discussed. The highest concentration of antidepressants was observed in the small river Utrata. In tap water only trace amounts of antidepressants including citalopram (up to 1.5ng/l), mianserin (up to 0.9ng/l), sertraline (<3.1ng/l), moclobemid (up to 0.3ng/l) and venlafaxine (up to 1.9ng/l) were detected. However this highlights their inadequate elimination in the drinking waste treatment facility. The presence of antidepressants in drinking water and the aquatic environment could have long-term effects even at low exposure level, especially since synergy amongst pharmaceutical pollutants may occur.

Reprint of "Effects of the SSRI citalopram on behaviours connected to stress and reproduction in Endler guppy, Poecilia wingei"

Psychoactive drugs, such as selective serotonin reuptake inhibitors (SSRI) have been identified in high levels in effluents from Swedish sewage treatment plants (STP) at concentrations high enough to give pharmacological effects in fish. In humans SSRIs are used in the treatment of depression and they have anxiolytic effects. In the present study we exposed Endler guppy (Poecilia wingei) of both sexes to citalopram that showed the highest concentrations of SSRIs in STP effluents and studied reproductive and non-reproductive behaviour. Male courting behaviours were not affected compared to control fish after 14-28 days exposure to 1 μgL(-1). In two experiments exposing both sexes to 0.2, 2.3 or 15 μgL(-1) for 21 days, fish exposed to the two highest doses showed anxiolytic effects when placed in a novel environment (novel tank diving test, NT). Males were only affected by exposure to 15 μgL(-1). They had significantly longer latency to explore the upper half of the aquarium, more visits and longer time spent in the upper half, and showed less bottom freezing behaviour, all markers of anxiolytic behaviour. In females exposure to 2.3 or 15 μgL(-1) significantly increased freezing behaviour, while no effects on other behaviour variables were observed. No effects on shoaling behaviour could be discerned. These results show that citalopram have anxiolytic effects on guppy fish and thus affect ecologically relevant behaviours of importance to survival of fish.