Comparison of milnacipran, duloxetine and pregabalin in the formalin pain test and in a model of stress-induced ultrasonic vocalizations in rats.

Milnacipran and duloxetine, serotonin/noradrenalin reuptake inhibitors, and pregabalin, a alpha(2)-delta(1) Ca(2+) channel blocker, are efficacious against fibromyalgia, a condition characterized by diffuse chronic pain and associated with stress. We compared these compounds (i.p. route), in rat models of acute/inflammatory pain (2.5% intraplantar formalin) and stress-induced ultrasonic vocalization (USV: 22kHz calls following presentation of a conditioned stimulus previously associated with foot-shocks). In the formalin test, milnacipran dose-dependently attenuated paw elevation and licking (minimal effective dose, MED: 2.5mg/kg for licking/late phase). Duloxetine was slightly more potent (MED=0.63). Pregabalin also reduced paw licking/late phase (MED=0.63), but was inactive up to 160mg/kg for paw elevation (both phases) and paw licking (early phase). Milnacipran dose-dependently reduced USV (MED=10, near total inhibition at 20mg/kg); duloxetine was less potent (MED=20). Pregabalin (2.5-80mg/kg) was only significantly active at 40mg/kg. Milnacipran, duloxetine and pregabalin possess analgesic activity in the formalin test on paw licking/late phase (corresponding to inflammatory pain with a central sensitization component). In the stress-induced USV model, milnacipran was the most potent and efficacious compound. To summarize, reduction of formalin-induced paw licking/late phase might constitute a useful indicator of potential activity against inflammatory/centrally sensitized pain, as might be expressed in fibromyalgia.

Noradrenoceptor antagonism with idazoxan improves L-dopa-induced dyskinesias in MPTP monkeys.

Treatment of Parkinson's disease with L-dopa is plagued in a majority of patients by dyskinesias. Noradrenaline/dopamine interactions are proposed on behavioral, biochemical, physiological and anatomical grounds. The aim of the study was to test the potential antidyskinetic effect of the alpha2-adrenoceptor antagonist, idazoxan, in a primate model of Parkinson's disease. Six female cynomolgus monkeys previously rendered parkinsonian by the toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and presenting an unchanged syndrome for several months were used. All responded readily to L-dopa but had developed dyskinesias which were manifested with each dose. In the first part of the study, seven doses of idazoxan (ranging from 0.25 mg/kg to 10 mg/kg, p.o.) were administered together with the vehicle or in combination with a fixed dose of L-dopa/benserazide (100/25 mg, p.o.). In the second part of the study, a fixed dose of idazoxan (7.5 mg/kg) was administered daily for 10 days and L-dopa was added to idazoxan on days 1, 4, 7 and 10. Vehicle (empty capsule) was used as control. Idazoxan, by itself (ranging from 5 mg/kg to 10 mg/kg), increased locomotor activity and improved the disability score with virtually no dyskinesias in three animals. In combination with L-dopa, idazoxan did not impair the antiparkinsonian response but significantly reduced dyskinesias in all six animals up to 65% at doses of 7.5 mg/kg and 10 mg/kg and delayed their onset, so that the "ON" state without dyskinesias was prolonged. The antidyskinetic effect of idazoxan was maintained when repeatedly administered for 10 days. On day 10, the locomotor response to L-dopa was significantly potentiated by chronic administration of idazoxan. Our results indicate that idazoxan has some antiparkinsonian effect of its own and may constitute a useful adjunct to L-dopa as it can reduce dyskinesias without impairing the relief of symptoms, this effect being maintained over time in this model.

Acute cardiovascular effects of the alpha2-adrenoceptor antagonist, idazoxan, in rats: influence of the basal sympathetic tone.

Intravenous administration of the alpha2-adrenoceptor antagonist, idazoxan, elicits variable cardiovascular effects, depending on experimental conditions. In this study, the effects of idazoxan were investigated in rats with high, low, or no basal sympathetic tone. In a group of conscious Sprague-Dawley rats (n = 9), mean arterial pressure (MAP), heart rate (HR), and renal sympathetic nervous activity (RSNA) were recorded. Idazoxan (250 microg/kg, i.v.) induced a transient decrease in MAP (-12+/-3 mm Hg) that was accompanied by increases in HR (49+/-14 beats/min) and RSNA (53+/-14%). In six of nine rats, a light pentobarbitone anesthesia was given. Basal RSNA was decreased (6.0+/-1.3 microV from 12.8+/-4.1 microV; p<0.05), and the depressor effect of idazoxan was reversed to a pressor effect (21+/-6 mm Hg) associated with bradycardia (-16+/-8 beats/min) and sympathoinhibition (-56+/-15%). In eight conscious intact rats, idazoxan (250 microg/kg, i.v.) attenuated by approximately 40% the pressor response to the selective alpha1-adrenoceptor agonist, cirazoline (0.5 microg/kg, i.v.). In three groups of six to seven ganglion-blocked (chlorisondamine, 2.5 mg/kg, i.v.) conscious rats, idazoxan dose-dependently increased mean arterial pressure (MAP: 39+/-2, 55+/-3, and 69+/-4 mm Hg at 125, 250, and 500 microg/kg, i.v., respectively) with minimal changes in HR. In contrast, the noradrenaline-releasing agent, tyramine (62.5, 125, and 250 microg/kg, i.v.), dose-dependently increased both MAP and HR. The alpha1-adrenoceptor antagonist, prazosin (1 mg/kg, i.v.; n = 8) blunted by approximately 70% (p<0.01) the pressor effect of 250 microg/kg idazoxan. It is concluded that in rats with high sympathetic tone, idazoxan has depressor effects, most likely related to its peripheral alpha-adrenoceptor antagonist properties. In rats with low or no sympathetic tone, idazoxan induced pressor responses mainly secondary to its partial agonist activity at vascular postjunctional alpha1-adrenoceptors.

Effect of the alpha 2 adrenoreceptor antagonist, idazoxan, on motor disabilities in MPTP-treated monkey.

1. The motor effect of the alpha 2 adrenoreceptor antagonist, idazoxan, was compared to that of L-dopa in MPTP-treated monkeys. 2. Idazoxan 2.0 mg/kg improved parkinsonian motor abnormalities which was comparable to the effects of a minimal effective dose of L-dopa. 3. At 2.0 and 5.0 mg/kg, the parkinsonian rigidity was the item most frequently alleviated by idazoxan (respectively 63.6% and 68.2%). 4. These findings provide support for the therapeutic utility of alpha 2 antagonists in the treatment of Parkinson's disease.

Pharmacokinetics, metabolism and bioavailability of the new anti-allergic drug BM 113. Part III: Pharmacokinetics, metabolism, dose dependency and gender effect after single or repeated administration to human healthy volunteers.

A new anti-allergic drug, BM 113 (1-(benzhydryloxyethyl)piperidino-4- ethylacetate, CAS 115313-90-1; BM 113 maleate: CAS 115313-91-2), with a piperidinic structure, showing anti-histaminic properties was studied after administration to healthy human volunteers. The focus was on the pharmacokinetics, the metabolism, the dose dependency and gender differences of the pharmacokinetic parameters of BM 113 and its main desacetylated metabolite, BM 212. Unchanged BM 113 was not recovered in plasma or in urine. The elimination of the radioactivity was essentially urinary with about 81% recovered within 24 h. The elimination was completed with 97% of the administered dose recovered after 120 h. HPLC dosage of BM 212, using a specific method, showed that BM 212 represented 62% of the urine radioactivity. The plasma profile of radioactivity was characterized by two decreasing phases with respective half-lives of 3.71 +/- 0.66 h and 24.67 +/- 25.01 h. A dose dependency study realised with 20, 40, 60 and 80 mg oral doses administered to 8 healthy volunteers has proven the linearity of the pharmacokinetics of BM 212 in the studied range. BM 212 disposition after single and repeated BM 113 oral doses in a 14-day study did not vary and permitted to conclude that no auto-induction or auto-inhibition phenomenon was involved. No significant difference between men and women was observed. The concentration profile was mono or biexponential, depending on the subject but whatever the gender. An inter-individual variability appeared for both sexes and caused some variations in the pharmacokinetic parameters.

Pharmacokinetics, metabolism and bioavailability of the new anti-allergic drug BM 113. Part II: Pharmacokinetics in primates after repeated oral or single intravenous administration.

The pharmacokinetics of BM 113 (1-(benzhydryloxyethyl)piperidino-4-ethylacetate, CAS 115313-90-1; BM 113 maleate: CAS 115313-91-2) was studied using 3H-BM 113 in the Cynomolgus primate. Oral repeated administration of 0.75 mg/kg was performed on 8 days. 40 days after the oral treatment, a single intravenous administration of 0.4 mg/kg was done. Whatever the administration route, the radioactivity excretion was essentially urinary (about 60%) and most of the radioactivity was excreted within the first 24 h. The faecal elimination was low, about 10% of the administered dose. 40 days after the treatment, some radioactivity was already present in the urine. For this reason, the excretion balance ranged from 70 to 83% of the dose. The elimination half-life of 3H-BM 113 was long, about 80 h.

Identification of I1 and I2 imidazoline receptors in striatum membranes from different species.

The alpha 2-adrenergic agonist [3H]clonidine and antagonist [3H]idazoxan also label I1 and I2 imidazoline receptors in striatum membranes. They are investigated here in striata from the dog, rat, mouse, rabbit, calf, monkey, and human. I1 receptors were barely detected in the dog, rat, and mouse and only further examined by competition binding experiments in calf, rabbit, and human. I2 receptors were further examined in all species. The centrally acting vasodilators clonidine and rilmenidine were more potent than moxonidine at the I1 receptors. They displayed low potency for the I2 receptors in all species except the rat. In all species examined, the nonsubstituted imidazoline derivatives idazoxan and RX801077 displayed high affinity for the I1 and I2 receptors. Conversely, both stereoisomers of the alkoxy-substituted imidazoline-derivative efaroxan displayed low affinity. The matching binding characteristics of these compounds further stress the structural similarity of the ligand binding sites of I1 and I2 receptors.

Pharmacokinetics, metabolism and bioavailability of the new anti-allergic drug BM 113. Part I: Pharmacokinetics and tissular distribution in Sprague-Dawley rats.

A new anti-allergic drug, BM 113 (1-(benzhydryloxyethyl)piperidino-4-ethylacetate, CAS 115313-90-1; BM 113 maleate: CAS 115313-91-2) with a piperidinic structure, showing antihistaminic properties was studied in male and female Sprague-Dawley rats after i.v. or p.o. administrations of 0.750 mg/kg 3H-BM 113. This product presented a rapid faecal elimination after i.v. and oral administration. The total recovery of the dose was obtained after 144 h. Biliary elimination was very fast: 54% of the intravenous dose were biliarily eliminated within 2 h, essentially as a conjugated form. For both i.v. and p.o. routes, the blood kinetics were biexponential. Intravenous administration led to elimination half-lives of 1.36 h and 0.75 h for the first phase and 38.6 h and 56.5 h for the second one for males and females, respectively. After oral administration, rebounds corresponding to the presence of enterohepatic cycle or metabolites were observed. Thus, the determination of half-lives was not possible. Slight but significant differences of some pharmacokinetic parameters were observed between genders. The results obtained during the protein binding study corresponded to the BM 113 metabolite known as BM 212. The free fraction corresponded to 55.5%. Tissular concentrations showed a rapid distribution of 3H-BM 113 followed by a slow elimination. In most of the tissues, the decrease was biexponential. The organs containing most of the radioactivity were those of the intestinal tract and the liver. Other tissues presented concentrations close to those of plasma. Lipidic tissues, showing low BM 113 concentrations, presented a slower elimination, probably related to the high lipophilicity of molecule.

Efaroxan, an alpha-2 antagonist, in the treatment of progressive supranuclear palsy.

We have tested, in a prospective randomized, double-blind, placebo-controlled, crossover, 12-week study, the effects of 2 mg efaroxan, a potent alpha-2 antagonist, given three times per day to 14 patients with progressive supranuclear palsy. Efaroxan did not induce any significant change on any motor assessment criteria. The present data do not confirm the assumption that the blockade of alpha-2 receptors might be a useful pharmacologic strategy to improve patients with progressive supranuclear palsy.

Validated method for the determination of idazoxan in human plasma by liquid chromatography with tandem mass spectrometric detection.

A liquid chromatography-tandem mass spectrometry method for the determination of idazoxan in human (heparin) plasma is presented, which was developed and validated using 500 microl of sample. Sample preparation consisted of the addition of fluoroidazoxan as the internal standard, extraction at alkaline conditions into tert.-butyl methyl ether, followed by centrifugation, evaporation of the solvent and reconstitution in methanol. After a short chromatographic run, detection took place by ionspray tandem mass spectrometry in positive ion mode. Validation results on linearity, specificity, accuracy, precision and stability, as well as application of the method to samples from a clinical trial, are shown. The validated calibration range is from 0.300 to 100 ng/ml, with accuracy (bias) and precision (coefficient of variation) being below 15% at all levels. A sample throughput of, typically, 150 per day can be achieved.

Pharmacological characterization of I1 and I2 imidazoline receptors in human striatum.

[3H]RX821002, [3H]clonidine and [3H]idazoxan have previously been shown to selectively label alpha 2-adrenergic receptors, I1 and I2 imidazoline receptors in the human central nervous system, respectively. Idazoxan shows relatively high affinity for all three receptors. We investigated the possible selectivity of several compounds towards one of those receptors in human striatum. Addition of an alkoxy group at the 2-position of the benzodioxan moiety of idazoxan (ethoxy-idazoxan, methoxy-idazoxan) increases the alpha 2-selectivity in human brain. Efaroxan is also alpha 2-selective. On the contrary, BU224, BU239, cirazoline and RX801077 display imidazoline receptor selectivity. Our results indicate that for all molecules tested, idazoxan and 'flat' analogs possess I1/I2 receptor selectivity. A 'bulky' substituent at the 2-position of the benzodioxan ring gives rise to alpha 2-adrenergic receptor selectivity. Until now, we found no more than 3-fold difference in IC50 between both imidazoline receptors. Both receptors also display similar stereoselectivity, suggesting that they might be 'interconnected' in the human striatum.

[Microcirculation and rheology]. / Microcirculation et rhéologie.

Microvessels, especially in the skin and muscles are organized in functional units. These units are controlled by the adrenergic system and hormones but also have autonomous metabolic and myogenic regulatory systems independent of vasomotion. Microcirculatory blood flow is affected by special rheologic properties: a low arteriolar haematocrit rises to the systemic level in the venules. The flow rate in the venules is low, and together with the raised haematocrit, explains the microvenular sensitivity to hyperviscosity. Capillarovenular microangiopathy, recently described by standard and fluorescent capillaroscopy, develops during chronic venous insufficiency. The capillary loops appear dilated and knotted together with fibrous deposits and pericapillary oedema. Venous hyperpressure is the cause of this microangiopathy. Together these phenomena disrupt normal haemodynamics and physiology of the microcirculatory unit: baseline hyperhaemia, lowered vasomotor and vasomotion reactivity, development of rheologic disorders (haemoconcentration, hyperfibrinogenaemia, erythrocyte agregation) and decreased fibrinolysis. Modifications in the transcapillary exchange is related to hypoxia and is aggravated by depressed lymphatic drainage. The main consequence is oedema. Inflammation, a characteristic of these microangiopathies could occur when the endothelium is activated by the hypoxia. The classical mediators of inflammation would activate interactions between the different cells: endothelium, granulocytes, monocytes and platelets. Several pharmacological models have been developed for the analysis of these data including exploration of the permeability and capillary resistance and rheological analysis. Objective observation of the microangiopathy with capillaroscopy, together with modern haemodynamical, biological and pharmacological methods are essential for a better understanding of microvascular disorders in chronic venous insufficiency.

Noradrenergic system: effect of DSP4 and FLA-57 on ethanol intake in ethanol preferring rats.

Ethanol preferring rats (male Long-Evans; n = 6) were selected as drinking rats (DR) and treated with DSP4 (50 mg.kg-1 IP) at the end of the preference selection. Two more groups received DSP4 (50 mg.kg-1 IP) + the inhibitor of dopamine beta-hydroxylase FLA-57 (1 mg.kg-1.d-1 during two weeks), IP (n = 5) or FLA-57 alone (1 mg.kg-1.d-1 during two weeks IP) (n = 5). The control DR group (n = 6) received NaCl 0.9%. 3H-Noradrenaline uptake was studied at the 17th day of treatment in DR, treated or not with DSP4, and in ethanol naive rats treated (n = 6) or not (n = 6) with DSP4 (50 mg.kg-1, IP) DSP4 does not modify ethanol intake in DR, and both treated groups (DR or ethanol naive rats). 3H-Noradrenaline uptake was decreased (about 60%), both in cortex and hippocampus. But the association of FLA-57 and DSP4 decreases both ethanol and fluid intakes. It was suggested 1) that the 40% of intact neurons was able to compensate the DSP4-induced noradrenergic neurons destruction, 2) that the destruction of noradrenergic pathways (FLA-57 + DSP4) is associated with a decrease in ethanol intake but also in fluid intakes, suggesting finally 3) that the modulation of ethanol intake by the noradrenergic system was partial or indirect.

Acamprosate appears to decrease alcohol intake in weaned alcoholics.

Five hundred and sixty-nine alcoholics were included in a double-blind placebo-controlled randomized multicenter study of the effects of Acamprosate (calcium acetylhomotaurinate (CA), 1.3 g/day) on indicators of alcoholic relapse after withdrawal. One hundred and eighty-one patients in the CA group versus 175 in the placebo group completed the three-month study. The major efficacy criterion was plasma gamma-glutamyl transpeptidase (GGT), as an indicator of recent alcohol ingestion. This analysis was completed by criteria concordance analysis on a number of indicators of alcohol intake. Patients in both groups were similar initially. After 3 months of treatment, the patients in the CA group had significantly lower GGT (1.4 +/- 1.56 versus 2.0 +/- 3.19 times normal, P = 0.016). All significant differences (P less than 0.05) or trends (0.10 greater than P greater than 0.05) were in favor of a superior effect of CA over placebo. The major side-effect of CA was diarrhea (present in 13% of CA patients versus 7% of placebo, P = 0.04). CA proved superior to placebo on the evolution of markers of alcohol ingestion at three months, in this large-scale multicenter study. It could be a new modality in the drug therapy of alcoholism, not involving an antabuse effect, an antidepressant action, or conditioning.

Application of an analytical method to calcium acetylhomotaurinate determination in urine.

After urine purification, plasma and urine concentrations of calcium acetylhomotaurinate (Acamprosate, CaAOTA) were determined with a high-performance liquid chromatography method following i.v. administration of the drug in two dogs. Results obtained in serum were in good agreement with those found previously. The CaAOTA urine determination is a promising method to be used in healthy volunteers.