Mirtazapine.

Mirtazapine is one of antidepression which is used mainly in the treatment of depression, moreover, it is sometimes used in the treatment of anxiety disorders, insomnia, nausea, and vomiting, and to produce weight gain when desirable. The action of mirtazapine is an antagonist of certain adrenergic and serotonin receptors, and, furthermore, the drug is used strong as antihistamine, and it is occasionally defined as a noradrenergic and specific serotonergic antidepressant (NaSSA). The comprehensive profile of mirtazapine gives more detailed information about nomenclature, formulae, elemental analysis, and appearance. In addition, the numerous methods of drug synthesis are summarized. Also the profile covers the physicochemical properties as: the value of pKa, drug solubility, melting point, X-ray powder diffraction, and analysis methods for example: (compendial, electrochemical, spectroscopic, and method of chromatographic). Besides that, the profile covered pharmacological profile and clinical pharmacokinetics in subtitle's (absorption, distribution, metabolism, and elimination). About 100 references were given as a proof of the above-mentioned studies.

[How to act when an alpha-blocker is associated with a potent inhibitor of CYP3A4]. / Conduite à tenir en cas d'association d'un alpha-bloquant et d'un inhibiteur puissant du cytochrome 3A4.

OBJECTIVE: Combination of alpha-blockers with potent CYP3A4 inhibitors is either contra-indicated or not recommended. We searched data supporting this classification and guiding prescribers when such an interaction occurs. METHODS: We analyzed reports published by the French agency for drug safety, reference books and performed search in databases of pharmacokinetics studies and case or case series related with these interactions. RESULTS: The classification of the potential severity of these interactions defined by the French agency for drug safety evolved over time. Our literature search did not identify any cases or case series reporting serious clinical consequences of such interactions and no pharmacoepidemiological studies on the association between alpha-blockers and inhibitors of CYP3A4. The content of the summaries of product characteristics indicate that the combination of ketoconazole with alfuzosin, silodosin and tamsulosin increases the area under the curve of the alpha-blocker 3 fold. CONCLUSION: Data demonstrating the clinical consequences of an association between alpha-blocker and a potent CYP3A4 inhibitor are lacking. The 3 fold increase of the area under the curve for alfuzosin, silodosin and tamsulosin associated with ketoconazole while the association with the two first is contra-indicated and is not recommended with the third raises questions. This lack of data leaves doctors and pharmacists in a situation of uncertainty on how to proceed when such an interaction occurs.

Effect of mirtazapine on rat bone tissue after orchidectomy.

OBJECTIVE: Our study aimed to investigate the effect of mirtazapine on bone metabolism in the orchidectomized rat model. METHODS: Rats were divided into three groups. A sham-operated control group (SHAM group) and a control group after orchidectomy (ORX group) received the standard laboratory diet (SLD). An experimental group after orchidectomy (ORX MIRTA group) received SLD enriched with mirtazapine for 12 weeks. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry. Bone marker concentrations of osteoprotegerin (OPG), amino-terminal propeptide of procollagen type I, bone alkaline phosphatase (BALP), sclerostin and bone morphogenetic protein 2 were examined in bone homogenate. The femurs were used for biomechanical testing. RESULTS: Compared with the control ORX group, we found a lower BMD in the ORX MIRTA group. The differences were statistically significant, although not in the lumbar vertebrae. BMD was lower in the MIRTA group, suggesting a preferential effect on cortical bone. However, although the thickness of the diaphyseal cortical bone was not different, the fragility in the femoral neck area was statistically significantly different between the groups in biomechanical testing. Regarding the bone metabolism markers, there was a significant decrease in OPG and BALP levels, suggesting a reduction in osteoid synthesis. CONCLUSIONS: The results suggest that prolonged use of mirtazapine may have a negative effect on the synthesis of bone and on its mechanical strength, especially in the femoral neck. Further studies are warranted to establish whether mirtazapine may have a clinically significant adverse effect on bone exclusively in the model of gonadectomized rats, or whether the effect occurs also in the model of gonadally intact animals and in respective human models.

Electroconvulsive shocks decrease α2-adrenoceptor binding in the Flinders rat model of depression.

Despite years of drug development, electroconvulsive therapy (ECT) remains the most effective treatment for severe depression. The exact therapeutic mechanism of action of ECT is still unresolved and therefore we tested the hypothesis that the beneficial effect of ECT could in part be the result of increased noradrenergic neurotransmission leading to a decrease in α2-adrenoceptor binding. We have previously shown that both the Flinders sensitive line (FSL) and Flinders resistant line (FRL) rats had altered α2-adrenoceptor binding compared to control Sprague-Dawley (SD) rats. In this study, we treated female FSL, FRL and SD rats with electroconvulsive shock (ECS), an animal model of ECT, or sham stimulation for 10 days before brains were removed and cut into 20µm thick sections. Densities of α2-adrenoceptors were measured by quantitative autoradiography in the hippocampus, thalamic nucleus, hypothalamus, amygdala, frontal cortex, insular cortex, and perirhinal cortex using the α2-adrenoceptor antagonist, [(3)H]RX 821002. ECS decreased the binding of α2-adrenoceptors in cortical regions in the FSL and cortical and amygdaloid regions in the control FRL rats compared to their respective sham treated group. The normal SD controls showed no significant response to ECS treatment. Our data suggest that the therapeutic effect of ECS may be mediated through a decrease of α2-adrenoceptors, probably due to a sustained increase in noradrenaline release. These data confirm the importance of the noradrenergic system and the α2-adrenoceptor in depression and in the mechanism of antidepressant treatments.

Spinal mechanism of micturition reflex inhibition by naftopidil in rats.

AIM: We investigated the spinal mechanism through which naftopidil inhibits the micturition reflex by comparing the effects of noradrenaline and naftopidil in rats. METHODS: The following were investigated: the influence of oral naftopidil on plasma monoamine and amino acid levels, the distribution of oral 14C-naftopidil, the effects of intravenous (IV) or intrathecal (IT) injection of noradrenaline or naftopidil on isovolumetric bladder contractions, amino acid levels in the lumbosacral spinal cord after IT noradrenaline or naftopidil, and the effects of IT naftopidil and strychnine and/or bicuculline on isovolumetric bladder contractions. KEY FINDINGS: Oral naftopidil decreased the plasma adrenaline level, while it increased the serotonin and glycine levels. After oral administration, 14C-naftopidil was detected in the spinal cord and cerebrum, as well as in plasma and the prostate gland. When the bladder volume was below the threshold for isovolumetric reflex contractions, IV (0.1mg) or IT (0.1µg) noradrenaline evoked bladder contractions, but IV (1mg) or IT (0.01-1µg) naftopidil did not. When the bladder volume was above the threshold for isovolumetric reflex contractions, IV or IT noradrenaline transiently abolished bladder contractions. IT noradrenaline decreased the levels of glycine and gamma-aminobutyric acid (GABA) in the lumbosacral cord, while IT naftopidil increased the GABA level. IT strychnine and/or bicuculline blocked the inhibitory effect of IT naftopidil on bladder contractions. SIGNIFICANCE: Naftopidil inhibits the micturition reflex by blocking α1 receptors, as well as by the activation of serotonergic, glycinergic, and GABAergic neurons in the central nervous system.

Effects of three antagonists on selected pharmacodynamic effects of sublingually administered detomidine in the horse.

OBJECTIVE: To describe the effects of alpha2 -adrenergic receptor antagonists on the pharmacodynamics of sublingual (SL) detomidine in the horse. STUDY DESIGN: Randomized crossover design. ANIMALS: Nine healthy adult horses with an average age of 7.6 ± 6.5 years. METHODS: Four treatment groups were studied: 1) 0.04 mg kg(-1) detomidine SL; 2) 0.04 mg kg(-1) detomidine SL followed 1 hour later by 0.075 mg kg(-1) yohimbine intravenously (IV); 3) 0.04 mg kg(-1) detomidine SL followed 1 hour later by 4 mg kg(-1) tolazoline IV; and 4) 0.04 mg kg(-1) detomidine SL followed 1 hour later by 0.12 mg kg(-1) atipamezole IV. Each horse received all treatments with a minimum of 1 week between treatments. Blood samples were obtained and plasma analyzed for yohimbine, atipamezole and tolazoline concentrations by liquid chromatography-mass spectrometry. Behavioral effects, heart rate and rhythm, glucose, packed cell volume (PCV) and plasma proteins were monitored. RESULTS: Chin-to-ground distance increased following administration of the antagonists, however, this effect was transient, with a return to pre-reversal values as early as 1 hour. Detomidine induced bradycardia and increased incidence of atrioventricular blocks were either transiently or incompletely antagonized by all antagonists. PCV and glucose concentrations increased with tolazoline administration, and atipamezole subjectively increased urination frequency but not volume. CONCLUSIONS AND CLINICAL RELEVANCE: At the doses administered in this study, the alpha2 -adrenergic antagonistic effects of tolazoline, yohimbine and atipamezole on cardiac and behavioral effects elicited by SL administration of detomidine are transient and incomplete.

Clinical Pharmacology of Alpha-1 Blockers Improving Drug-profile through Novel Formulations.

Clinical pharmacology is an essential consideration in chronic therapies, and may play a significant role in modifying the pharmacological characteristics of drug formulations. Improvement in drug formulations may ensure their safe and effective use over a period of time. This has been particularly observed with α-1 adrenergic blockers in hypertension management. Advancements in formulations like prazosin GITS, have resulted in improvement in tolerability profile and smoother, more effective blood pressure control, which reasonably translate into improvement in patient compliance and better clinical outcomes.

Pharmacokinetics and pharmacodynamic effects of tolazoline following intravenous administration to horses.

Tolazoline is an α2-adrenergic receptor antagonist, used in veterinary medicine to antagonize the central nervous system depressant and cardiovascular effects of α2 receptor agonists. The pharmacokinetics and pharmacodynamic effects of tolazoline when administered subsequent to detomidine in the horse were recently reported, although the reversal of the sedative and cardiovascular effects following detomidine may not be complete. The current study therefore investigated the pharmacokinetics and pharmacodynamic effects of tolazoline when administered as a sole agent. Nine healthy adult horses were administered tolazoline (4mg/kgIV) and blood samples were collected at time 0 (prior to drug administration) and at various times up to 72h post drug administration. Plasma samples were analyzed using liquid chromatography-mass spectrometry and resulting data analyzed using compartmental analysis. Systemic clearance, steady state volume of distribution and terminal elimination half-life were 0.820±0.182L/h/kg, 1.68±0.379L/kg and 2.69±0.212h, respectively. Tolazoline administration had no effect on chin to ground distance, but the heart rate decreased (relative to baseline) and the percentage of atrial-ventricular block increased in all horses within 2min of administration. Packed cell volume and glucose concentrations were also increased throughout the sampling period. While not commonly used as a sole agent, caution is indicated whenever tolazoline is administered since the effects may be unpredictable.

Yokukansan inhibits morphine tolerance and physical dependence in mice: the role of α2A-adrenoceptor.

Yokukansan (YKS) is a traditional Japanese medicine consisting of seven medicinal herbs that is used for the treatment of neurosis, insomnia, and the behavioral/psychological symptoms of dementia. This study examined the effects of YKS on morphine tolerance and physical dependence in mice. Daily oral administration of YKS (0.5 or 1.0 g/kg) for 3 weeks significantly attenuated morphine tolerance and naloxone-precipitated morphine withdrawal signs (jumps and body weight loss) without affecting the analgesic effect of morphine. The inhibitory effect of YKS on withdrawal jumps in morphine-dependent mice was blocked by a single pretreatment with an α(2)-adrenoceptor antagonist, yohimbine, but not by an α(1)-adrenoceptor antagonist, prazosin. A similar inhibitory effect on withdrawal jumps was observed by repeated administration of yohimbine. The membrane expression of α(2A)-adrenoceptors in the pons/medulla was decreased in morphine withdrawn animals; this reduction was prevented by repeated administration of YKS or yohimbine. Competitive radioligand and [(35)S]guanosine-5'-O-(3-thiotriphosphate) binding assays revealed that YKS and its constituent herbs, Glycyrrhiza (GR) and Uncaria hook (UH), had specific binding affinity for and antagonist activity against the α(2A)-adrenoceptor. Certain chemical constituents, including GR -derived glycyrrhizin and its metabolite, 18ß-glycyrrhetinic acid, and UH-derived geissoschizine methyl ether (GME), shared such activities. Repeated administration of GR, UH, glycyrrhizin or GME significantly inhibited morphine withdrawal signs. These results suggest that YKS and its active constituents inhibit morphine tolerance and physical dependence, and that the latter is due at least in part to the prevention of the decreased membrane expression of the α(2A)-adrenoceptor in the brainstem by its prolonged blockade.

Mirtazapine to reduce methamphetamine use: a randomized controlled trial.

CONTEXT: No approved pharmacologic treatments for methamphetamine dependence exist. Methamphetamine use is associated with high morbidity and is a major cofactor in the human immunodeficiency virus epidemic among men who have sex with men (MSM). OBJECTIVE: To determine whether mirtazapine would reduce methamphetamine use among MSM who are actively using methamphetamine. DESIGN: Double-blind, randomized, controlled, 12-week trial of mirtazapine vs placebo conducted from September 5, 2007, to March 4, 2010. SETTING: San Francisco Department of Public Health. PARTICIPANTS: Participants were actively using, methamphetamine-dependent, sexually active MSM seen weekly for urine sample collection and substance use counseling. INTERVENTIONS: Random assignment to daily oral mirtazapine (30 mg) or placebo; both arms included 30-minute weekly substance use counseling. MAIN OUTCOME MEASURES: The primary study outcome was reduction in methamphetamine-positive urine test results. Secondary outcomes were study medication adherence (by self-report and medication event monitoring systems) and sexual risk behavior. RESULTS: Sixty MSM were randomized, 85% of follow-up visits were completed, and 56 participants (93%) completed the final visit. In the primary intent-to-treat analysis, participants assigned to the mirtazapine group had fewer methamphetamine-positive urine test results compared with participants assigned to the placebo group (relative risk, 0.57; 95% CI, 0.35-0.93, P = .02). Urine positivity decreased from 67% (20 of 30 participants) to 63% (17 of 27) in the placebo arm and from 73% (22 of 30) to 44% (12 of 27) in the mirtazapine arm. The number needed to treat to achieve a negative weekly urine test result was 3.1. Adherence was 48.5% by medication event monitoring systems and 74.7% by self-report; adherence measures were not significantly different between arms (medication event monitoring systems, P = .82; self-report, P = .92). Most sexual risk behaviors decreased significantly more among participants taking mirtazapine compared with those taking placebo (number of male partners with whom methamphetamine was used, P = .009; number of male partners, P = .04; episodes of anal sex with serodiscordant partners, P = .003; episodes of unprotected anal sex with serodiscordant partners, P = .003; episodes of insertive anal sex with serodiscordant partners, P = .001). There were no serious adverse events related to study drug or significant differences in adverse events by arm (P ≥ .99). CONCLUSION: The addition of mirtazapine to substance use counseling decreased methamphetamine use among active users and was associated with decreases in sexual risk despite low to moderate medication adherence. Trial Registration  clinicalTrials.gov Identifier NCT00497081.

A bioequivalence study of two tamsulosin sustained-release tablets in Indonesian healthy volunteers.

The bioavailability of two 0.4 mg tamsulosin sustained-release film-coated tablet formulations was compared; using generic tablets (Prostam(®)) as test formulation and the originator product as reference formulation. Twenty-four subjects were included in this single-dose, open-label, randomized two-way crossover design following an overnight fasting. A one-week wash-out period was applied. Blood samples were drawn up to 72 h following drug administration. Plasma concentration of tamsulosin was determined by liquid chromatography-tandem mass spectrometry method with TurboIonSpray mode. Pharmacokinetic parameters AUC(0-t,) AUC(0-∞), C (max) and t (½) were determined and used for bioequivalence evaluation after log-transformation, whereas t (max) ratios were evaluated non-parametrically. The estimated point and 90% confidence intervals (CI) for AUC(0-t,) AUC(0-∞), C (max) and t (½) were 109.55% (96.41-124.49%), 109.94% (96.85-124.81%), 105.87% (92.88-120.67%) and 100.00% (90.56-110.43%), respectively. These results indicated that the two formulations of tamsulosin were bioequivalent; therefore they may be prescribed interchangeably.

α1-Adrenoceptors and muscarinic receptors in voiding function - binding characteristics of therapeutic agents in relation to the pharmacokinetics.

In vivo and ex vivo binding of α(1)-adrenoceptor and muscarinic receptors involved in voiding function is reviewed with therapeutic agents (α(1)-adrenoceptor antagonists: prazosin, tamsulosin and silodosin; and muscarinic receptor antagonists: oxybutynin, tolterodine, solifenacin, propiverine, imiafenacin and darifenacin) in lower urinary tract symptoms. This approach allows estimation of the inhibition of a well-characterized selective (standard) radioligand by unlabelled potential drugs or direct measurement of the distribution and receptor binding of a standard radioligand or radiolabelled form of a novel drug. In fact, these studies could be conducted in various tissues from animals pretreated with radioligands and/or unlabelled novel drugs, by conventional radioligand binding assay, radioactivity measurement, autoradiography and positron emission tomography. In vivo and ex vivo receptor binding with α(1)-adrenoceptor antagonists and muscarinic receptor antagonists have been proved to be useful in predicting the potency, organ selectivity and duration of action of drugs in relation to their pharmacokinetics. Such evaluations of drug-receptor binding reveal that adverse effects could be avoided by the use of new α(1)-adrenoceptor antagonists and muscarinic receptor antagonists for the treatment of lower urinary tract symptoms. Thus, the comparative analysis of α(1)-adrenoceptor and muscarinic receptor binding characteristics in the lower urinary tract and other tissues after systemic administration of therapeutic agents allows the rationale for their pharmacological characteristics from the integrated viewpoint of pharmacokinetics and pharmacodynamics. The current review emphasizes the usefulness of in vivo and ex vivo receptor binding in the discovery and development of novel drugs for the treatment of not only urinary dysfunction but also other disorders.

Studies on the pharmacokinetics and pharmacodynamics of mirtazapine in healthy young cats.

Mirtazapine pharmacokinetics was studied in 10 healthy cats. Blood was collected before, and at intervals up to 72 h after, oral dose of 3.75 mg (high dose: HD) or 1.88 mg (low dose: LD) of mirtazapine. Liquid chromatography coupled to tandem mass spectrometry was used to measure mirtazapine, 8-hydroxymirtazapine and glucuronide metabolite concentrations. Noncompartmental pharmacokinetic modeling was performed. Median half-life was 15.9 h (HD) and 9.2 h (LD). Using Mann-Whitney analysis, a statistically significant difference between the elimination half-life, clearance, area under the curve (AUC) per dose, and AUC(∞) /dose of the groups was found. Mirtazapine does not appear to display linear pharmacokinetics in cats. There was no significant difference in glucuronidated metabolite concentration between groups. Pharmacodynamics was studied in 14 healthy cats administered placebo, LD and HD mirtazapine orally once in a crossover, blinded trial. In comparison with placebo, cats ingested significantly more food when mirtazapine was administered. No difference in food ingestion was seen between HD and LD, but significantly more behavior changes were seen with the HD. Limited serum sampling during the pharmacodynamic study revealed drug exposure comparable with the pharmacokinetic study, but no correlation between exposure and food consumed. Mirtazapine (LD) was administered daily for 6 days with no drug accumulation detected.

Silodosin for the treatment of benign prostatic hyperplasia: pharmacology and cardiovascular tolerability.

Relief of benign prostatic hyperplasia (BPH)-related lower urinary tract symptoms by α-blockers (α1-adrenoceptor antagonists) is mediated primarily through the blockade of α(1A)-receptors, leading to relaxation of smooth muscle in the prostate and bladder neck. Early α-blockers that were nonselective for adrenoceptor subtypes have been associated with blood pressure-related adverse effects, such as orthostatic hypotension, that may be attributed at least in part to the blockade of α(1B)-adrenoceptors in arterial vessels. Silodosin, a novel α-blocker with exceptionally high selectivity for α(1A-) versus α(1B)-adrenoceptors, was recently approved in the United States for the treatment of urinary symptoms related to BPH. The unique receptor selectivity profile likely accounts for some of the desirable clinical features of the drug. Silodosin possesses an excellent cardiac- and blood pressure-related safety profile, and data have demonstrated that it does not promote QT-interval prolongation. Therapeutic doses of silodosin are safe for men with mild-to-moderate liver dysfunction; dosage adjustment is recommended in those with moderate renal impairment. The drug should not be taken with potent cytochrome P450 3A4 inhibitors. Silodosin may be especially beneficial in patients who need to maximize cardiovascular tolerability.

Population pharmacokinetics of tamsulosin hydrochloride in paediatric patients with neuropathic and non-neuropathic bladder.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: Tamsulosin is available on prescription as a modified release capsule in the US (Flomax), and in most European countries for the treatment of the signs and symptoms of benign prostatic hyperplasia (BPH). The pharmacokinetics of tamsulosin hydrochloride (HCl) have been extensively studied in adults, but no pharmacokinetic data for paediatrics have been published to date. WHAT THIS STUDY ADDS: A population pharmacokinetic model of tamsulosin HCl was developed in paediatric patients. Covariate analysis revealed that body weight and alpha(1)-acid glycoprotein influenced both the apparent clearance and the apparent volume of distribution. This study confirms that there is no major difference in the pharmacokinetics of tamsulosin HCl between paediatrics (age range 2-16 years) and adults when the effect of body weight is taken into consideration. AIMS: The main objective of this study was to characterize the population pharmacokinetics of tamsulosin hydrochloride (HCl) in paediatric patients with neuropathic and non-neuropathic bladder. A secondary objective was to compare the pharmacokinetics in paediatric patients and adults. METHODS: Tamsulosin HCl plasma concentrations in 1082 plasma samples from 189 paediatric patients (age range 2-16 years) were analyzed with NONMEM, applying a one compartment model with first-order absorption. Based on the principles of allometry, body weight was incorporated in the base model, along with fixed allometric exponents. Covariate analysis was performed by means of a stepwise forward inclusion and backward elimination procedure. Simulations based on the final model were used to compare the pharmacokinetics with those in adults. RESULTS: Beside the priori-implemented body weight, only alpha(1)-acid glycoprotein had an effect on both apparent clearance and apparent volume of distribution. No other investigated covariates, including gender, age, race, patient population and concomitant therapy with anti-cholinergics, significantly affected the pharmacokinetics of tamsulosin HCl (P < 0.001). The results of simulations indicated that the exposure in 12.5 kg paediatric patients was 3.5-4.3 fold higher than that in 70.0 kg adults. After a weight-based dose administration, the exposure in paediatric patients was comparable with that in healthy adults. CONCLUSIONS: A population pharmacokinetic model of tamsulosin HCl in paediatric patients was established and it described the data well. There was no major difference in the pharmacokinetics of tamsulosin HCl between paediatric patients (age range 2-16 years) and adults when the effect of body weight was taken into consideration.

Extrapolating in vitro metabolic interactions to isolated perfused liver: predictions of metabolic interactions between R-bufuralol, bunitrolol, and debrisoquine.

Drug-drug interactions (DDIs) are a great concern to the selection of new drug candidates. While in vitro screening assays for DDI are a routine procedure in preclinical research, their interpretation and relevance for the in vivo situation still represent a major challenge. The objective of the present study was to develop a novel mechanistic modeling approach to quantitatively predict DDI solely based upon in vitro data. The overall strategy consisted of developing a model of the liver with physiological details on three subcompartments: the sinusoidal space, the space of Disse, and the cellular matrix. The substrate and inhibitor concentrations available to the metabolizing enzyme were modeled with respect to time and were used to relate the in vitro inhibition constant (K(i)) to the in vivo situation. The development of the liver model was supported by experimental studies in a stepwise fashion: (i) characterizing the interactions between the three selected drugs (R-bufuralol (BUF), bunitrolol (BUN), and debrisoquine (DBQ)) in microsomal incubations, (ii) modeling DDI based on binary mixtures model for all the possible pairs of interactions (BUF-BUN, BUF-DBQ, BUN-DBQ) describing a mutual competitive inhibition between the compounds, (iii) incorporating in the binary mixtures model the related constants determined in vitro for the inhibition, metabolism, transport, and partition coefficients of each compound, and (iv) validating the overall liver model for the prediction of the perfusate kinetics of each drug determined in isolated perfused rat liver (IPRL) for the single and paired compounds. Results from microsomal coincubations showed that competitive inhibition was the mechanism of interactions between all three compounds, as expected since those compounds are all substrates of rat CYP2D2. For each drug, the K(i) values estimated were similar to their K(m) values for CYP2D2 indicative of a competition for the same substrate-binding site. Comparison of the performance between the novel liver physiologically based pharmacokinetic (PBPK) model and published empirical models in simulating the perfusate concentration-time profile was based on the area under the curve (AUC) and the shape of the curve of the perfusate time course. The present liver PBPK model was able to quantitatively predict the metabolic interactions determined during the perfusions of mixtures of BUF-DBQ and BUN-DBQ. However, a lower degree of accuracy was obtained for the mixtures of BUF-BUN, potentially due to some interindividual variability in the relative proportion of CYP2D1 and CYP2D2 isoenzymes, both involved in BUF metabolism. Overall, in this metabolic interaction prediction exercise, the PBPK model clearly showed to be the best predictor of perfusate kinetics compared to more empirical models. The present study demonstrated the potential of the mechanistic liver model to enable predictions of metabolic DDI under in vivo condition solely from in vitro information.

Pharmacokinetics and pharmacodynamics of tamsulosin in its modified-release and oral controlled absorption system formulations.

Tamsulosin is an alpha(1)-adrenoceptor antagonist used for the treatment of lower urinary tract symptoms that are suggestive of benign prostatic hyperplasia. It is mostly used in a modified-release (MR) formulation, but an oral controlled absorption system (OCAS) and a 'without-water' tablet formulation are also available in some countries. The oral bioavailability of the MR formulation in the fasted state is close to 100%. Whereas absorption from the MR formulation is affected by concomitant food intake, that of the OCAS formulation is food independent. Tamsulosin exhibits high plasma-protein binding, largely to alpha(1)-acid glycoprotein. It is metabolized, mainly by cytochrome P450 (CYP) 3A4 and CYP2D6 to compounds with low abundance, and 8.7-15% of an oral dose is excreted renally as the parent compound. The pharmacokinetics of tamsulosin are not affected to a major extent by age, and pharmacokinetic alterations in renally impaired patients relate largely to an increased concentration of alpha(1)-acid glycoprotein. Pharmacokinetic alterations with hepatic impairment are also only moderate, thus neither renal nor mild to moderate hepatic impairment necessitates dose adjustment. Concomitant exposure to potent CYP3A4 inhibitors can more than double the exposure of tamsulosin. Clinical studies have indicated that despite its lower bioavailability, the OCAS formulation has the same treatment efficacy as the MR formulation but causes somewhat fewer cardiovascular adverse effects.

Efficacy and safety of tamsulosin for the treatment of non-neurogenic voiding dysfunction in females: a 8-week prospective study.

We evaluated the therapeutic effects of tamsulosin for women with non-neurogenic voiding dysfunction. Women who had voiding dysfunctions for at least 3 months were included. Inclusion criteria were age > or =18 yr, International Prostate Symptom Score (IPSS) of > or =15, and maximum flow rate (Q(max)) of > or =12 mL/sec and/or postvoid residuals (PVR) of > or =150 mL. Patients with neurogenic voiding dysfunction or anatomical bladder outlet obstruction were excluded. All patients were classified according to the Blaivas-Groutz nomogram as having no or mild obstruction (group A) or moderate or severe obstruction (group B). After 8 weeks of treatment, treatment outcomes and adverse effects were evaluated. One hundred and six patients were evaluable (70 in group A, 36 in group B). After treatments, mean IPSS, bother scores, Q(max), PVR, diurnal and nocturnal micturition frequencies and scored form of the Bristol Female Lower Urinary Tract Symptoms questionnaire (BFLUTS-SF) were changed significantly. Eighty-nine patients (84%) reported that the treatment was beneficial. The proportion of patients reported that their bladder symptoms caused "moderate to many severe problems" were significantly decreased. No significant difference were observed between the groups in terms of IPSS, bother score, Q(max), PVR, micturition frequency, and BFLUTS-SF changes. Adverse effects related to medication were dizziness (n=3), de novo stress urinary incontinence (SUI) (n=3), aggravation of underlying SUI (n=1), fatigue (n=1). Tamsulosin was found to be effective in female patients with voiding dysfunction regardless of obstruction grade.

A LC-MS-MS method for determination of low doxazosin concentrations in plasma after oral administration to dogs.

A rapid and sensitive reversed phase liquid chromatography- tandem mass spectrometry (LC-MS-MS) method is developed for the determination of doxazosin in canine plasma. The samples are prepared by precipitation of proteins using a mixture of methanol and acetonitrile, followed by freezing and evaporation of the organic solvent. The remaining dry residue is redissolved in mobile phase and analyzed by LC-MS-MS with positive electrospray ionization using the selected reactions monitoring mode. An XTerra MS C(18) column, a mobile phase composed of acetonitrile and 2mM ammonium acetate with gradient elution, and a flow rate of 400 microL/min are employed. The elution times for prazosin (internal standard) and doxazosin are approximately 8 and 10 min, respectively. Calibration curves are linear in the 1-20 ng/mL concentration range. Limits of detection and quantification are 0.4 ng/mL and 1.2 ng/mL, respectively. Recovery is higher than 94%. Intra- and inter-day relative standard deviations are below 7% and 8%, respectively. The method is applied for the determination of doxazosin plasma levels following a single administration of doxazosin base and doxazosin mesylate tablets (2 mg dose) to dogs in the fed state. The results indicate possible superiority of the mesylate salt on the plasma input rates of doxazosin.