Pharmacokinetics of mirtazapine and its main metabolites after single intravenous and oral administrations in rats at two dose rates

BACKGROUND

Mirtazapine (MRZ) is a human antidepressant drug metabolized to 8-OH mirtazapine (8-OH) and dimethylmirtazapine (DMR) metabolites. Recently, this drug has been proposed as a potential analgesic for use in a multidrug analgesic regime in the context of veterinary medicine. The aim of this study was to assess the pharmacokinetics of MRZ and its metabolites DMR and 8-OH in rats.

FINDINGS

Eighteen fasted, healthy male rats were randomly divided into 3 groups (n = 6). Animals in these groups were respectively administered MRZ at 2 and 10 mg/kg orally and 2 mg/kg intravenously. Plasma MRZ and metabolite concentrations were evaluated by HPLC-FL detection method. After intravenous administration, MRZ was detected in all subjects, while DMR was only detected in three. 8-OH was not detected. After oral administration, MRZ was detected in 3 out of 6 rats treated with 2 mg/kg, it was detected in 6 out of 6 animals in the 10 mg/kg group. DMR was only detectable in the latter group, while 8-OH was not detected in either group. The oral bioavailability was about 7% in both groups.

CONCLUSIONS

The plasma concentration of the MRZ metabolite 8-OH was undetectable, and the oral bioavailability of the parental drug was very low.

A Rapid and Sensitive HPLC-Fluorescence Method for Determination of Mirtazapine and Its two Major Metabolites in Human Plasma

A rapid and sensitive HPLC method has been developed for the quantification of mirtazapine (MRZ), a noradrenergic and specific serotonergic inhibitor antidepressant (NaSSA) and its two major metabolites N-desmethyl mirtazapine (NDM) and 8-hydroxymirtazapine (8-OHM) in human plasma. The separation was achieved using Chromolith C18 column and a mobile phase of acetonitrile: phosphate buffer (pH = 3, 20:80, v/v) in isocratic mode at a flow rate of 2 mL/min. A fluorescence detector was set at 290 and 350 nm for excitation and emission, respectively. Zolpidem was used as the internal standard. Liquid-liquid extraction was applied for sample clean up. All analytes were eluted in less than 5 minutes with LOQ of 1 ng/mL for MRZ and 2 ng/mL for both NDM and 8-OHM. The developed method was successfully applied to quantify MRZ and its metabolites in plasma of a healthy volunteer.

[Occupational diseases caused by artificial optical radiation (AOR)]

BACKGROUND

Italian national legislation guarantees safety and health for workers exposed to artificial optical radiations (AOR) by Legislative Decree 81/2008.

OBJECTIVES AND METHODS

Effects and damages to health resulting from AOR exposure were analyzed from literature data.

RESULTS

Ultraviolet radiations (UV), particularly those in the wavelength range between 220 and 310 nm, causes chronic conjunctivitis and kerato-conjunctivitis. Skin cancer caused by UV exposure included basal cell carcinoma, squamous cell carcinoma and melanoma. As regards Infrared Radiations (portion of the spectrum between 780 nm and 1 mm), the biological effect is essentially of thermal nature. Exposure to blue light (portion ofthe spectrum of visible light radiation in a wavelength range between 380 and 550 nm) causes exclusively retinal damage and is considered to be responsible for the development of situations of age-related macular degeneration (AMD). Even if experimental data are available, at the present time there is still no epidemiological evidence of retinal damage caused by blue light.

CONCLUSIONS

The forensic criteria for investigating the causality link between occupational exposure to AOR and damage, and the methodology necessary for the assessment process, are reported. Two lists of occupational diseases which were included in the Italian Ministerial Decrees, issued respectively on April 2008 and 11 December 2009, are also considered. Lastly, on the basis of the current existing guidelines and scientific evidence, the authors propose occupational health surveillance protocols for workers exposed to AOR risk.

Development and validation of a new GC-MS method for the detection of tramadol, O-desmethyltramadol, 6-acetylmorphine and morphine in blood, brain, liver and kidney of Wistar rats treated with the combination of heroin and tramadol

Heroin is one of the most dangerous abused drugs in the world. Tramadol is an additive recently found at high concentration levels in street heroin seizures in Egypt. This substance could affect the usual analytical method for the detection of heroin and metabolites, as well as the pharmacokinetic and disposition of single analytes. One shortfall regarding this issue is present in the literature. This study describes a validated, simple, sensitive and selective method to determine tramadol, O-desmethyltramadol, 6-acetylmorphine and free morphine in the blood, brain, liver and kidney of Wistar rats, intraperitoneally treated with a combination of heroin and tramadol (10 and 70 mg/kg, respectively) using liquid-liquid extraction and gas chromatography-mass spectrometry detection. The calibration curves of tramadol, O-desmethyltramadol and 6-acetylmorphine in blood were linear in the concentration range from 25-5,000 ng/mL and morphine was found in the concentration range 50-5,000 ng/mL. The analytes were detected in all tested matrices, except 6-acetylmorphine, which was not detected in liver. The highest concentrations of tramadol and O-desmethyltramadol were observed in kidney (22,9381 and 28,498 ng/g), while 6-acetylmorphine and morphine were found at the highest levels in brain (3,280 and 3,899 ng/g, respectively). The present method is simple, rapid and sensitive and can be used to study the pharmacokinetics, disposition and interaction of these drugs in several animal models.

[Work at high altitudes: risk factors and health surveillance]

Work at high altitude (elevation equal to or greater than 3000 m above sea level) results in a physiological adaptation of the human organism to changing environmental conditions. The main problem related to the altitude is represented by the reduction of partial pressure of oxygen (hypoxia). Our study takes into consideration occupational risk factors: those related to physical environment of high altitude; those related to the worker; those related to the characteristics of the job. It is finally addressed the decision making process related to the formulation of the judgment of suitability for performance of work activities at high altitude. The health protocol proposed requires an accurate anamnestic investigation aimed at gathering information on pre-existing pathophysiological conditions that need, once identified, clinical and instrumental tests specific and targeted. These clinical protocols are analyzed and proposed for the main pathophysiologic conditions that pose a risk to health at high altitude.

First measurement of chiral dynamics in π- γ → π- π- π+

The COMPASS Collaboration at CERN has investigated the π- γ → π- π- π+ reaction at center-of-momentum energy below five pion masses, sqrt[s]<5m(π), embedded in the Primakoff reaction of 190 GeV pions impinging on a lead target. Exchange of quasireal photons is selected by isolating the sharp Coulomb peak observed at smallest momentum transfers, t'<0.001  GeV2/c2. Using partial-wave analysis techniques, the scattering intensity of Coulomb production described in terms of chiral dynamics and its dependence on the 3π-invariant mass m(3π)=sqrt[s] were extracted. The absolute cross section was determined in seven bins of sqrt[s] with an overall precision of 20%. At leading order, the result is found to be in good agreement with the prediction of chiral perturbation theory over the whole energy range investigated.

Pilot in vivo toxicological investigation of boron nitride nanotubes

Boron nitride nanotubes (BNNTs) have attracted huge attention in many different research fields thanks to their outstanding chemical and physical properties. During recent years, our group has pioneered the use of BNNTs for biomedical applications, first of all assessing their in vitro cytocompatibility on many different cell lines. At this point, in vivo investigations are necessary before proceeding toward realistic developments of the proposed applications. In this communication, we report a pilot toxicological study of BNNTs in rabbits. Animals were injected with a 1 mg/kg BNNT solution and blood tests were performed up to 72 hours after injection. The analyses aimed at evaluating any acute alteration of hematic parameters that could represent evidence of functional impairment in blood, liver, and kidneys. Even if preliminary, the data are highly promising, as they showed no adverse effects on all the evaluated parameters, and therefore suggest the possibility of the realistic application of BNNTs in the biomedical field.

PDE10A and PDE10A-dependent cAMP catabolism are dysregulated oppositely in striatum and nucleus accumbens after lesion of midbrain dopamine neurons in rat: a key step in parkinsonism physiopathology

Loss of dopamine neurons in experimental parkinsonism results in altered cyclic nucleotide cAMP and cGMP levels throughout the basal ganglia. Our objective was to examine whether expression of phosphodiesterase 10A (PDE10A), an isozyme presenting a unique distribution in basal ganglia, is altered after unilateral injection of 6-hydroxydopamine in the medial forebrain bundle, eliminating all midbrain dopaminergic neurons, such that cyclic nucleotide catabolism and steady state could be affected. Our study demonstrates that PDE10A mRNA levels were decreased in striatal neurons 10 weeks after 6-hydroxydopamine midbrain lesion. Such changes occurred in the striatum ipsilateral to lesion and were paralleled by decreased PDE10A protein levels and activity in striatal neurons and in striato-pallidal and striato-nigral projections. However, PDE10A protein and activity were increased while PDE10A mRNA was unchanged in the nucleus accumbens ipsilateral to the 6-hydroxydopamine midbrain lesion. Accordingly, cAMP levels were down-regulated in the nucleus accumbens, and up-regulated in the striatum ipsilateral to the lesion, but they were not significantly changed in substantia nigra and globus pallidus. Unlike cAMP, cGMP levels were decreased in all dopamine-deafferented regions. The opposite variations of cAMP steady state in striatum and nucleus accumbens are concordant and likely dependent, at least in part, on the down-regulation of PDE10A expression and activity in the former and its up-regulation in the latter. On the other hand, the down-regulation of cGMP steady state in the striato-nigral and striato-pallidal complex is not consistent with and is likely independent from the concomitant down-regulation of PDE10A. Therefore, dopamine loss inversely regulates PDE10A gene expression in the striatum and PDE10A post-transcription in the nucleus accumbens, therein differentially modulating PDE10A-dependent cAMP catabolism.

Observation of a J(PC)=1-+ exotic resonance in diffractive dissociation of 190 GeV/c π- into π- π- π+

The COMPASS experiment at the CERN SPS has studied the diffractive dissociation of negative pions into the π- π- π+ final state using a 190  GeV/c pion beam hitting a lead target. A partial wave analysis has been performed on a sample of 420,000 events taken at values of the squared 4-momentum transfer t' between 0.1 and 1  GeV2/c2. The well-known resonances a1(1260), a2(1320), and π2(1670) are clearly observed. In addition, the data show a significant natural-parity exchange production of a resonance with spin-exotic quantum numbers J(PC)=1-+ at 1.66  GeV/c2 decaying to ρπ. The resonant nature of this wave is evident from the mass-dependent phase differences to the J(PC)=2-+ and 1++ waves. From a mass-dependent fit a resonance mass of (1660±10(-64)(+0))  MeV/c2 and a width of (269±21(-64)(+42))  MeV/c2 are deduced, with an intensity of (1.7±0.2)% of the total intensity.

Evaluation of tramadol and its main metabolites in horse plasma by high-performance liquid chromatography/fluorescence and liquid chromatography/electrospray ionization tandem mass spectrometry techniques

Tramadol is a centrally acting analgesic drug that has been used clinically for the last two decades to treat pain in humans. The clinical response of tramadol is strictly correlated to its metabolism, because of the different analgesic activity of its metabolites. O-Desmethyltramadol (M1), its major active metabolite, is 200 times more potent at the micro-receptor than the parent drug. In recent years tramadol has been widely introduced in veterinary medicine but its use has been questioned in some species. The aim of the present study was to develop a new sensible method to detect the whole metabolic profile of the drug in horses, through plasma analyses by high-performance liquid chromatography (HPLC) coupled with fluorimetric (FL) and photodiode array electrospray ionization mass spectrometric (PDA-ESI-MS) detection, after its sustained release by oral administration (5 mg/kg). In HPLC/FL experiments the comparison of the horse plasma chromatogram profile with that of a standard mixture suggested the identification of the major peaks as tramadol and its metabolites M1 and N,O-desmethyltramadol (M5). LC/PDA-ESI-MS/MS analysis confirmed the results obtained by HPLC/FL and also provided the identification of two more metabolites, N-desmethyltramadol (M2), and N,N-didesmethyltramadol (M3). Another metabolite, M6, was also detected and identified. The present findings demonstrate the usefulness and the advantage of LC/ESI-MS/MS techniques in a search for tramadol metabolites in horse plasma samples.

Lowered cAMP and cGMP signalling in the brain during levodopa-induced dyskinesias in hemiparkinsonian rats: new aspects in the pathogenetic mechanisms

Dysregulation of dopamine receptors is thought to underlie levodopa-induced dyskinesias in experimental models of Parkinson's disease. It is unknown whether an imbalance of the second messengers, cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), is involved in the alterations of levodopa/dopamine signal transduction. We examined cAMP and cGMP signalling in the interconnected cortico-striatal-pallidal loop at the peak of levodopa-induced dyskinesias in rats with 6-hydroxydopamine lesions in the substantia nigra. In addition, we examined the role of phosphodiesterase (PDE) and the rate of cAMP and cGMP degradation on the severity of levodopa-induced dyskinesias in animals pretreated with PDE inhibitor, zaprinast. Unilateral lesion of substantia nigra led to an increase in cAMP but a decrease in cGMP levels in the ipsilateral basal ganglia. After chronic levodopa treatment, cAMP and cGMP were differentially regulated in eukinetic animals: the cAMP level increased in the cortex and striatum but decreased in the globus pallidus of both hemispheres, whereas the cGMP decreased below baseline levels in the contralateral cortico-striatal-pallidal regions. In dyskinetic animals chronic levodopa treatment led to an absolute decrease in cAMP and cGMP levels in cortico-striatal-pallidal regions of both hemispheres. Pretreatment with zaprinast reduced the severity of levodopa-induced dyskinesias, and partly prevented the decrease in cyclic nucleotides compared with pretreatment with saline-levodopa. In conclusion, using a rat model of hemiparkinsonism, we observed a significant reduction in the levels of cyclic nucleotides in both hemispheres at the peak of levodopa-induced dyskinesias. We propose that such a decrease in cyclic nucleotides may partly result from increased catabolism through PDE overactivity.

RANTES and human sperm fertilizing ability: effect on acrosome reaction and sperm/oocyte fusion

Beta-chemokine, regulated on activation and normally T-cell expressed and presumably secreted (RANTES), is present in both the male and female genital tract fluids where its levels increase in diseases related to infertility, such as endometriosis and male genital tract infections. beta-Chemokine receptors (CCR3 and CCR5) are expressed on freshly ejaculated human sperm cells and a sperm chemoattractant effect for RANTES has been reported. No information exists on other possible roles of RANTES on sperm functions involved in the fertilization process. In the present study, the exposure of sperm suspensions to high concentrations of the chemokine, comparable to those observed in inflammatory diseases, significantly decreased the stimulatory effect exerted by progesterone on sperm/oocyte fusion, evaluated by means of the hamster egg penetration test. Accordingly, a large proportion of spermatozoa preincubated under capacitating conditions with high concentrations of RANTES underwent a premature acrosome reaction (AR) that prevented subsequent progesterone-induced AR. Finally, sperm samples exposed to the same high levels of chemokine showed a significant increase in the intracellular levels of cAMP, which is involved in capacitation and AR dynamics. These results indicate a negative interference of high levels of RANTES on the sperm fertilizing ability, thereby suggesting a potential contribution of this chemokine to subfertility associated with endometriosis and genital tract inflammatory diseases.

High performance liquid chromatographic determination of thalidomide in patients affected by hepatocellular carcinoma

The present study developed a validate and precise reversed-phase high performance liquid chromatography (HPLC) method for the determination of thalidomide (T) in plasma, to quantify T in patients affected by hepatocellular carcinoma. Twelve male subjects aging from 62 to 82 years and weighting 66-88kg, were orally administered with single dose of T (200mg/BW). Two ml of stabilizer-solution (CH3OH/CH3CN, 1/1 (v/v)+CH3COOH 2%) were added to 1ml of human plasma and stoked to -80 degrees C until analyses. This moisture (1.38microl) was added with 20microl of CF3COOH and 100microl of phthalimide (IS) 1.75microg/ml, vortexed and centrifuged. Surnatant (800microl) was dried under vacuum at room temperature, added with 50microl of appropriate solution and injected onto HPLC. T and IS were detected at UV wavelength of 220nm with a run time of 10min. Mobile phase was 10mM pH 5.5NH4+CH3COO-/CH3CN, 75/25 (v/v) buffer at flow rate of 1.5ml/min. Inter-day and intra-day variation coefficient was <10% with an error of accuracy <10%. The present detection method was able to quantify T to every withdrawal time period (LOD 0.05microg/ml). The IS used in the present study had the same wavelength maximum absorption of T, differently from early UV detection methods reported in literature where phenacetin was used. Pharmacokinetic parameters belonging from the present study are not significantly different from those calculated in previously studies performed in human health subjects and patients affected by other pathology.

Better Mycophenolic Acid 12-Hour Trough Level After Enteric-Coated Mycophenolate Sodium in Patients With Gastrointestinal Intolerance to Mycophenolate Mofetil

INTRODUCTION

Enteric-coated mycophenolate sodium (EC-MPS) is the enteric-coated salt form of mycophenolic acid (MPA), the active component of the prodrug mycophenolate mofetil. EC-MPS was developed to reduce the upper-gastrointestinal (GI) effects of mycophenolate mofetil. There are no studies available comparing trough plasma levels in patients with GI intolerance to MMF when they are converted to EC-MPS.

AIM

To compare the GI tolerance and the MPA levels in patients previously treated with MMF in whom this drug was replaced by EC-MPS.

MATERIALS AND METHODS

A prospective study was conducted in 133 renal transplant patients after conversion from MMF to EC-MPS (median time posttransplant 42 months, range 1 to 240 months). The causes for EC-MPS switching were GI intolerance to MMF (51.9%; group A), low trough plasma levels with MMF (29.3%; group B), and others (18.8%; group C). These patients were converted to equipotent doses of EC-MPS.

RESULTS

The trough plasma MPA levels increased from 1.5 +/- 1.1 microg/mL at baseline to 2.5 +/- 2.0 microg/mL at 1 month postconversion despite the equipotent EC-MPS doses not being increased. These higher plasma levels were maintained throughout the study. In group A, this increase was from 1.8 +/- 1.0 to 2.7 +/- 2.1 microg/mL (P = .01) and in group B from 0.8 +/- 0.4 to 2.4 +/- 1.4 microg/mL (P < .001). The doses and levels of calcineurin inhibitor decreased from baseline. Creatinine clearance improved from 56.5 +/- 24.7 mg/dL at baseline to 61.9 +/- 28.6 at 6 months postconversion (P = .02). There was a statistically significant increase in hemoglobin levels. In group A, the GI tolerance improved in 78% of the patients.

CONCLUSIONS

At equipotent doses, patients converted to EC-MPS have higher and more adequate levels of MPA. At 6 months postconversion, we observed an improvement of the renal function, probably due to a reduction of calcineurin inhibitor drugs. However, the possibility that a better immunosuppressive efficacy as demonstrated by more suitable trough plasma levels may have been a contributing factor cannot be discarded.

Study of Anemia After Late Introduction of Everolimus in the Immunosuppressive Treatment of Renal Transplant Patients

INTRODUCTION

mTOR inhibitors (imTOR) are immunosuppressive drugs that have a concentration-related effects on hematopoiesis, potentially resulting in anemia. The reason is uncertain, but a pathogenic link between sirolimus-induced anemia and the appearance of an inflammatory state was recently suggested. Because inflammation-related anemia is characterized by a functional iron deficiency, we studied whether everolimus influenced iron homeostasis.

METHODS

We studied iron homeostasis in 43 patients after late introduction of everolimus into the immunosuppressive treatment. Thirty-seven patients (86%) were receiving mycophenolate. Hemoglobin concentration, red blood cell count, mean corpuscular volume, serum iron, ferritin, C-reactive protein levels, and transferrin saturation were evaluated 3 months before and 1, 3, and 6 months after the switch.

RESULTS

The percentage of anemic patients preconversion was 18.6% and it was 34.9% at 3 months and 18.6% at 6 months. We did not observe a significant reduction in hemoglobin, but there was increased red blood cell count after everolimus introduction, with a significant reduction in mean corpuscular volume. Serum iron and transferrin saturation levels were also markedly reduced after the switch, while ferritin serum concentrations remained stable. An improvement in renal function was observed.

CONCLUSIONS

The anemia caused by everolimus--microcytosis, low serum iron, despite high ferritinemia, and elevated C-reactive protein levels--was consistent with the anemia of a chronic inflammatory state. This alteration occurred within the first months postconversion and disappeared at 6 months. The combination of mycophenolate and everolimus seemed to be useful without significant secondary effects.

[Diagnosis and insurance compensation of occupational diseases in construction industry]

The aim of this study is to evaluate the outcome of 302 occupational diseases in building workers detected by UOOML Ospedali Riuniti of Bergamo and notified to INAIL from 2000 to 2005. The 41.3% of cases were accepted as work-related. Among remaining cases (58.7%), INAIL rejected 40.9% for lack or absence of documentation. 59.1% for no adhesion to legal medicine criteria. By analysis of occupational diseases detected in the last 5 years, we found an increase of muscle-skeletal disorders, for which, now, diagnostic procedure and insurance evaluation are difficult. This work shows a wide gap between reported occupational diseases of buildings workers and compensation given by INAIL. These results underlines the need of comparison among involved institutions in order to standardize statistical and diagnostic instruments.