In Vivo Monitoring of Dopamine by Microdialysis with 1 min Temporal Resolution Using Online Capillary Liquid Chromatography with Electrochemical Detection

Microdialysis is often applied to understanding brain function. Because neurotransmission involves rapid events, increasing the temporal resolution of in vivo measurements is desirable. Here, we demonstrate microdialysis with online capillary liquid chromatography for the analysis of 1 min rat brain dialysate samples at 1 min intervals. Mobile phase optimization involved adjusting the pH, buffer composition, and surfactant concentration to eliminate interferences with the dopamine peak. By analyzing electrically evoked dopamine transients carefully synchronized with the switching of the online LC sample valve, we demonstrate that our system has both 1 min sampling capabilities and bona fide 1 min temporal resolution. Evoked DA transients were confined to single, 1 min brain dialysate samples. After uptake inhibition with nomifensine (20 mg/kg i.p.), responses to electrical stimuli of 1 s duration were detected.

Dopamine-independent locomotor actions of amphetamines in a novel acute mouse model of Parkinson disease

Brain dopamine is critically involved in movement control, and its deficiency is the primary cause of motor symptoms in Parkinson disease. Here we report development of an animal model of acute severe dopamine deficiency by using mice lacking the dopamine transporter. In the absence of transporter-mediated recycling mechanisms, dopamine levels become entirely dependent on de novo synthesis. Acute pharmacological inhibition of dopamine synthesis in these mice induces transient elimination of striatal dopamine accompanied by the development of a striking behavioral phenotype manifested as severe akinesia, rigidity, tremor, and ptosis. This phenotype can be reversed by administration of the dopamine precursor, L-DOPA, or by nonselective dopamine agonists. Surprisingly, several amphetamine derivatives were also effective in reversing these behavioral abnormalities in a dopamine-independent manner. Identification of dopamine transporter- and dopamine-independent locomotor actions of amphetamines suggests a novel paradigm in the search for prospective anti-Parkinsonian drugs.

Identification of dopamine transporter- and dopamine- independent locomotor actions of amphetamines suggests a novel paradigm in the search for prospective anti-Parkinsonian drugs.

[Dopaminergic regulation of theta activity of septohippocampal neuron in the awake rabbit]

The effects of dopamine reuptake blocker nomifensine and nonselective antagonist of dopamine receptors haloperidol on the theta rhythmicity of the medial septal neurons and hippocampal EEG were investigated in the rabbit. Bilateral intracerebroventricular infusion of nomifensine (9 micrograms in each ventriculus) produced an increase in both the rate of firing and the theta modulation of medial septal neurons; the theta power of the hippocampal EEG also augmented. The degree of neuronal theta stability (time constant of damping, tao theta) significantly increased. The frequency of rhythmic bursts in the neuronal firing also substantially elevated. The amplitude, regularity and frequency of theta waves in the hippocampal EEG also increased. The antagonist haloperidol (12.5 mg) caused the opposite effect. The theta activity of medial septal neurons and the theta power of the hippocampal EEG decreased after haloperidol injection. Theta rhythmicity of septal neurons significantly diminished, the rate of rhythmic bursts in the neuronal firing also decreased, although not substantially. The theta amplitude and regularity in the hippocampal EEG also decreased. Effects of both drugs built up rapidly and then gradually attenuated. Nomifensine infusion against the background of exposure to haloperidol provoked neither increasing neuronal firing rate, nor elevating theta activity. These finding suggest that dopaminergic system produces activation of the septohippocampal system in situations that require selective attention to functionally important information.

Enhanced attention in rhesus monkeys as a common factor for the cognitive effects of drugs with abuse potential

RATIONALE

One of the common neurochemical features of many drugs of abuse is their ability to directly or indirectly enhance dopaminergic activity in the brain, particularly within the ventral tegmental-nucleus accumbens pathway. Dopaminergic pathways in the frontal and limbic cortex also may be targets for these agents, where pharmacological effects could result in heightened attention and/or support self-administration behavior.

OBJECTIVES

The purpose of this study was to determine whether drugs from differing pharmacological classes that exhibit abuse potential would share the ability to counter distractability in the delayed matching task.

METHODS

Well trained mature macaques performed a computer-assisted delayed matching-to-sample task which included trials associated with three delay intervals and randomly interspersed task-relevant distractors. Drug regimens included four to five doses and subjects were tested no more than twice per week.

RESULTS

All but one of the six compounds (tomoxetine), on average, increased task accuracy for either non-distractor or distractor trials. It was evident that for several compounds, doses required to improve accuracy for non-distractor trials were routinely greater than the doses required to improve accuracy for distractor trials. Data for the individualized Best dose (based upon the subject's optimal level of accuracy during distractor trials) revealed statistically significant distractor-related improvements in task accuracy for the same five compounds. The relative efficacy for reversing distractor-induced decrements in task accuracy was estimated by the level of improvement with respect to baseline: nomifensine (31%)>nicotine (22%) approximately morphine (19%) approximately caffeine (19%) approximately methylphenidate (22%) >tomoxetine (9%). Tomoxetine (noradrenergic preferring) was the only compound that did not produce a significant improvement in accuracy.

CONCLUSIONS

These results provide pharmacological support for the concept that attentional mechanisms may play an important role in the "environmental" associative aspects of drug seeking behavior, and as such they may provide the basis for treatment strategies aimed at preventing relapse in detoxified addicts.

Preferential increases in nucleus accumbens dopamine after systemic cocaine administration are caused by unique characteristics of dopamine neurotransmission

In vivo voltammetry was used to investigate the preferential increase of extracellular dopamine in the nucleus accumbens relative to the caudate-putamen after systemic cocaine administration. In the first part of this study, cocaine (40 mg/kg, i.p.) was compared with two other blockers of dopamine uptake, nomifensine (10 mg/kg, i.p.) and 3beta-(p-chlorophenyl)tropan-2beta-carboxylic acid p-isothiocyanatophenylmethyl ester hydrochloride (RTI-76; 100 nmol, i.c.v.), to assess whether the inhibitory mechanism of cocaine differed in the two regions. All three drugs robustly increased electrically evoked levels of dopamine, and cocaine elevated dopamine signals to a greater extent in the nucleus accumbens. However, kinetic analysis of the evoked dopamine signals indicated that cocaine and nomifensine increased the K(m) for dopamine uptake whereas the dominant effect of RTI-76 was a decrease in V(max). Under the present in vivo conditions, therefore, cocaine is a competitive inhibitor of dopamine uptake in both the nucleus accumbens and caudate-putamen. Whether the preferential effect of cocaine was mediated by regional differences in the presynaptic control of extracellular DA that are described by rates for DA uptake and release was examined next by a correlation analysis. The lower rates for dopamine release and uptake measured in the nucleus accumbens were found to underlie the preferential increase in extracellular dopamine after cocaine. This relationship explains the paradox that cocaine more effectively increases accumbal dopamine despite identical effects on the dopamine transporter in the two regions. The mechanism proposed for the preferential actions of cocaine may also mediate the differential effects of psychostimulant in extrastriatal regions and other uptake inhibitors in the striatum.

A comparison of the patterns of striatal Fos-like immunoreactivity induced by various dopamine agonists in rats

In contrast to the highly patchy patterns of Fos-like immunoreactivity seen in the rostral striatum after administration of a number of dopamine agonists, the monoamine uptake blocker cocaine has been reported to produce a relatively homogeneous pattern of gene expression. In the current study we extended these observations by using a quantitative technique to demonstrate that while amphetamine and apomorphine produce patchy striatal Fos expression, the selective dopamine uptake inhibitors amfonelic acid, nomifensine and GBR-12909 all, like cocaine, produce near random patterns of gene expression. These findings suggest that the production of relatively 'non-patchy' patterns of immediate early gene expression may be a general property of dopamine transport inhibitors unrelated to any unique pharmacological properties of cocaine.

Changes in seizure susceptibility to local anesthetics by repeated administration of cocaine and nomifensine but not GBR12935: possible involvement of noradrenergic system

We examined cross-sensitization of cocaine and synthetic local anesthetics to their seizure susceptibility after repeated administration. Seizure susceptibility of procaine and lidocaine increased after the end of two days of treatment with a subconvulsive dose of cocaine. Acute treatment with nomifensine but not GBR12935, a specific inhibitor of the dopamine transporter, facilitated lidocaine-induced convulsion. Furthermore, daily treatment with nomifensine for two days enhanced lidocaine-induced convulsion. These results suggest the possible involvement of the brain noradrenergic system in the changes in seizure susceptibility after repeated administration of some local anesthetics.

Ethanol effects on self-administration of alfentanil, cocaine, and nomifensine in rhesus monkeys

A common form of polydrug use is that of cocaine and ethanol. The identification of an ethanol-cocaine combination product, cocaethylene, with properties in common with cocaine, has led to speculation that this metabolite may contribute to the co-abuse of cocaine and ethanol. In order to determine whether ethanol pretreatments selectively altered cocaine's reinforcing potency, ethanol pretreatments were given to monkeys trained to press levers and receive IV infusions of several doses of cocaine or alfentanil. In addition, nomifensine, a drug which has a mechanism of action similar to cocaine's, was evaluated in the presence and absence of ethanol in monkeys with the cocaine baseline history. Ethanol, in doses ranging from 100 to 1780 mg/kg, given 10 min before the 130-min session, had no effect on responding maintained by alfentanil. These doses also had no significant effect on cocaine-maintained responding, although the potency of cocaine as a reinforcer was increased following administration of 1000 mg/kg ethanol in two of the four subjects. The potency of nomifensine as a reinforcer was significantly increased by 1000 mg/kg ethanol, but again, this enhancement was limited to the same two subjects. These data indicate that, in this paradigm, cocaethylene did not selectively modify cocaine's reinforcing potency, but there appear to be individual differences with respect to ethanol's ability to stimulate rates of drug-maintained responding.

Habit-forming actions of nomifensine in nucleus accumbens

Rats learned to lever-press when reinforced with response-contingent microinfusions of the dopamine uptake inhibitor nomifensine (1.7 nmol per injection) into the ventro-medial (shell) region of nucleus accumbens septi (NAS). The drug was not effective when similar injections were given either in random relation to lever-pressing, into the more dorso-lateral (core) region of NAS, or into the frontal cortex. Cocaine was also effective in NAS, but considerably less so. These data suggest that response-contingent dopamine uptake blockade within the NAS is sufficient to establish and maintain instrumental response habits.

Effect of local infusion of glutamate analogues into the nucleus accumbens of rats: an electrochemical and behavioural study

In vivo voltammetry at electrochemically pretreated carbon fibre electrodes was used to investigate the effect of local infusion of glutamate analogues on dopamine (DA) release in rat nucleus accumbens. Infusion of a low dose of NMDA or AMPA (1 mM/0.2 microliter), but not L-glutamate or kainate, was followed a few minutes later by a large but short-lived increase in the extracellular concentration of DA. The involvement of spreading depression was indicated since this response could be repeated only after a short refractory period, and the response magnitude did not seem to be dependent on the dose infused. Furthermore, the increase in DA release was accompanied by a marked negative shift in brain field potential and a similar increase in release could be induced by local infusion of K+. The infusion of NMDA, AMPA or kainate was followed by behavioural activation of the animals but not convulsions. The behavioural response induced by NMDA was dose-dependently reduced by haloperidol, which suggests the involvement of a DA-dependent mechanism in this effect. Co-infusion of the DA transport inhibitors, nomifensine or GBR 12909, failed to alter the DA response to NMDA, while this response was completely blocked by co-infusion of tetrodotoxin or pretreatment with reserpine. It is evident from this study that local infusion of NMDA or AMPA may induce spreading depression in rat nucleus accumbens and that this condition is associated with a vast release of DA and behavioural activation.

Clearance of exogenous dopamine in rat dorsal striatum and nucleus accumbens: role of metabolism and effects of locally applied uptake inhibitors

In vivo electrochemistry was used to investigate the mechanisms contributing to the clearance of locally applied dopamine in the dorsal striatum and nucleus accumbens of urethane-anesthetized rats. Chronoamperometric recordings were continuously made at 5 Hz using Nafion-coated carbon fiber electrodes. When a finite amount of dopamine was pressure-ejected at 5-min intervals from a micropipette adjacent to the electrode, transient and reproducible dopamine signals were detected. Substitution of L-alpha-methyldopamine, a substrate for the dopamine transporter but not for monoamine oxidase, for dopamine in the micropipette did not substantially alter the time course of the resulting signals. This indicates that metabolism of locally applied dopamine to 3,4-dihydroxy-phenylacetic acid is not responsible for the decline in the dopamine signal. Similarly, changing the applied oxidation potential from +0.45 to +0.80 V, which allows for detection of 3-methoxytyramine formed from dopamine via catechol-O-methyltransferase, had little effect on signal amplitude or time course. In contrast, lesioning the dopamine terminals with 6-hydroxydopamine, or locally applying the dopamine uptake inhibitors cocaine or nomifensine before pressure ejection of dopamine, significantly increased the amplitude and time course of the dopamine signals in both regions. The effects of cocaine and nomifensine were greater in the nucleus accumbens than in the dorsal striatum. Local application of lidocaine and procaine had no effect on the dopamine signals. Initial attempts at modeling resulted in curves that were in qualitative agreement with our experimental findings. Taken together, these data indicate that (1) uptake of dopamine by the neuronal dopamine transporter, rather than metabolism or diffusion, is the major mechanism for clearing locally applied dopamine from the extracellular milieu of the dorsal striatum and nucleus accumbens, and (2) the nucleus accumbens is more sensitive to the effects of inhibitors of dopamine uptake than is the dorsal striatum.

Acute therapy of depression

The acute therapy (the initial 8 weeks of treatment) of depression (including the whole spectrum of "less than major," "major," and "more than major") has been reviewed comparing the old tricyclics with the new generations (especially mianserin, moclobemide, and the serotonin selective reuptake inhibitors (SSRIs), i.e., citalopram, fluoxetine, fluvoxamine, paroxetine, and sertraline). The Hamilton Rating Scale for Depression has been used to measure clinical efficacy. Statistically, the method of meta-analysis has been applied. The results showed that the SSRIs and moclobemide are equal to the tricyclics. Mianserin is inferior to tricyclics as well as to SSRIs. The antidepressive profile of the SSRIs is nonsedation but still with anxiolytic effects. The safety profile of the SSRIs is much more benign than that of the tricyclics.

DuP 753, a nonpeptide angiotensin II-1 receptor antagonist, alters dopaminergic function in rat striatum

The purpose of this study was to determine if the nonpeptide angiotensin II-1 receptor antagonist DuP 753 after, acute or chronic administration in vivo or after in vitro exposure, altered indices of dopaminergic function in rat striatum. In vivo studies examined the effect of acute and chronic 21-day administration of DuP 753 (10 mg/kg, s.c.) on levels of dopamine (DA) and its metabolite, dihydroxyphenylacetic acid (DOPAC). To determine if chronic treatment with DuP 753 was able to inhibit the pressor response to angiotensin II, a single i.v. dose of angiotensin II (0.1 microgram/kg) was administered 18 hours after the last dose of DuP 753. Acute DuP 753 resulted in significantly decreased (14%) levels of DA. Chronic DuP 753 resulted in increased (1.64 fold) levels of DOPAC, although DA levels were not altered. The single i.v. administration of angiotensin II resulted in increased (88%) DOPAC levels regardless of chronic DuP 753. The in vitro effect of DuP 753 (0.1 nM-1.0 microM) on basal and field stimulation-evoked release of DA and DOPAC was determined in superfused striatal slices from drug naive rats. DA was not detected in these experiments. DuP 753 did not alter basal outflow of DOPAC. At low concentrations (1.0-10 nM), DuP 753 decreased (53%) stimulation-evoked DOPAC overflow; however, at concentrations greater than 10 nM, the inhibitory effect was diminished. Nomifensine (10 microM; a DA uptake inhibitor) was included in the superfusion buffer in order to measure the effect of DuP 753 on the concentration of DA in superfusate. DuP 753 had no effect on basal DA and DOPAC outflow.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of amphetamine and nomifensine on intracranial self-stimulation discrimination behavior in rats

Rats implanted with electrodes in the medial forebrain bundle-lateral hypothalamus were trained in a discrete trial procedure to make a differential response (right or left lever press) in the presence or absence of brain stimulation [intracranial self-stimulation (ICSS)]. When animals reached a high level of accuracy (95% correct) in the discrimination task, testing was begun. In the first experiment, we compared the effects of saline and 0.3 mg/kg d-amphetamine when the intertrial interval (ITI) was 1, 5, 10, and 15 s. In the second experiment, animals were tested either with saline, 0.3 mg/kg d-amphetamine, or 1, 3, or 10 mg/kg nomifensine and the ITI was held constant at 5 s. Increasing the ITI from 1-15 s did not produce a drug-induced change in the discriminative stimulus properties of ICSS, although it did produce changes in total numbers of lever presses and numbers of intertrial lever presses. In the second experiment, neither d-amphetamine nor nomifensine altered the discriminative stimulus properties of ICSS, but a dose-response increase occurred in the time to complete the test session and in total number of lever presses and in presses on the initiating lever. Under conditions known to increase extracellular dopamine (DA) levels in brain, both amphetamine and nomifensine produced large increases in locomotor activity, but neither drug produced changes in the detection threshold for ICSS. Results indicated that the internal cues produced by ICSS are different from those produced by these psychomotor stimulant drugs.

Characterization and pharmacological responsiveness of dopamine release recorded by microdialysis in the substantia nigra of conscious rats

The extracellular concentration of dopamine (DA) and 3,4-dihydroxyphenylacetic acid in the substantia nigra (SN) and striatum was estimated by microdialysis. The dialysate content of DA from the SN was recorded during infusion of a DA uptake blocker (nomifensine; 5 mumol/L) dissolved in the perfusion fluid. Perfusion of tetrodotoxin (1 mumol/L) produced a virtually complete disappearance of nigral and striatal DA release. Dendritic as well as terminal release of DA was inhibited for several hours when the nerve impulse flow in dopaminergic neurons was blocked by systemic administration of gamma-butyrolactone (750 mg/kg, i.p.). The systemic administration (0.3 mg/kg, i.p.) as well as infusion (1 mumol/L) of the D2 agonist (-)-N-0437 [2-(n-propyl-N-2-thienylethylamino)-5-hydroxytetralin] produced a significant decrease in the release of DA in both the striatum and the SN. DA levels were recorded in the striatum both with and without addition of nomifensine to the perfusion fluid. The decrease in the striatum after (-)-N-0437 was suppressed in the presence of nomifensine. Infusion (1 mumol/L) as well as systemic administration (40 mg/kg) of sulpiride caused a similar increase in the release of striatal DA; this increase was, in both experiments, potentiated by nomifensine coinfusion. Sulpiride administration induced a small increase in the release of nigral DA. Infusion of (-)-N-0437 or (-)-sulpiride into the nigra caused a moderate decrease and increase, respectively, of striatal DA level.(ABSTRACT TRUNCATED AT 250 WORDS)

Follow-up study on 24 patients with nomifensine-induced immune haemolytic anaemia

There is as yet only scarce information regarding the natural history and long-term clinical sequelae of patients who survive the acute complications of severe drug-related immune haemolysis, the effect of the mode of drug administration for sensitization and possible alterations of serological characteristics of drug-dependent antibodies during the postsensitization period. We therefore followed 24 patients with nomifensine-induced haemolytic anaemia for up to 6 years after the haemolytic attack. All patients had suffered from a severe haemolytic episode. None of the patients showed any abnormal findings upon reinvestigation (complete history and physical examination; extended biochemical and haematological laboratory status), particularly with respect to renal function. Drug-dependent antibodies remained detectable in 19 of 21 sera, while drug-independent autoantibodies, demonstrable in six patients during the acute phase of haemolysis, could no longer be detected. With regard to the mode of drug administration, the majority of patients (15 out of 24) had developed the haemolysis at the beginning (immediately after a single dose) or during a second course of drug therapy (n = 8 and 7, respectively). The immune response did not appear to be dose- or time-dependent. This study confirms the benign long-term prognosis of patients who survive life-threatening complications in drug-induced immune haemolytic anaemia. In addition, it indicates that drug-dependent antibodies may remain detectable over long periods of time, and that irregular drug administration might be associated with a higher risk of drug sensitization.

Nomifensine maleate in adult attention deficit disorder

The authors studied 18 adults (8 men and 10 women) in an open trial of nomifensine maleate for the treatment of attention deficit disorder (ADD). All patients met DSM-III criteria and the Utah criteria for ADD, residual type (RT). Medication effect was measured at week 1 and week 4 of treatment using the Structured Interview for ADD-H Symptoms. Data from week 4 showed that all eight men and seven of the women responded well to nomifensine, showing a significant decrease in ADD with hyperactivity symptoms. Side effects were minimal, consisting of drowsiness, dry mouth, headache, and nausea. One responder (5%) was taken off the medicine after developing an allergic reaction. Results showed that short-term use of nomifensine was relatively free from side effects and was remarkably effective in the treatment of ADD-RT. The authors discussed the implications of the use of nomifensine and related drugs in the treatment of ADD-RT.

Intracerebroventricular administration of 1-methyl-4-phenylpyridinium ion in mice: effects of simultaneously administered nomifensine, deprenyl, and 1-t-butyl-4,4-diphenylpiperidine

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) destroys nigrostriatal dopaminergic pathways and thereby produces a syndrome similar to Parkinson's disease. MPTP is oxidized by monoamine oxidase B (MAO B) to the 1-methyl-4-phenylpyridinium ion (MPP+), which is taken up in dopaminergic neurons through the dopamine (DA) uptake system, where it develops its toxic effect. Our observations show a new aspect of the MPP+ mode of action, in which deprenyl in mice has a partially protective effect against MPP+. Furthermore budipine, a therapeutic agent for Parkinsonism, is also able to partially prevent MPP+ toxicity. A MAO B-inhibitory component of budipine, as shown in receptor binding studies previously, could contribute to this effect. Comparable experiments with nomifensine do not exclude the possibility of budipine as an effect as a DA uptake inhibitor. An unexplained after effect of budipine leads to a large increase in 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) levels five weeks after the last administration.

Suppressive effects of intraventricular injected dopamine and nomifensine on muricide induced by thiamine deficiency

The effects of dopamine (DA) and nomifensine (NF) on muricide activity induced by thiamine deficiency were examined. The chronic administration of L-dopa and nomifensine during feeding of thiamine deficient diet attenuated the muricide activity. Moreover, acute administration of L-dopa or nomifensine (IP) and dopamine or nomifensine (ICV) suppressed the thiamine deficiency-induced muricide activity dose-dependently. Small doses of apomorphine inhibited the muricide response significantly. The suppressive effects of dopamine and nomifensine were antagonized by pretreatment with 6-hydroxydopamine, but were not changed by pretreatment with p-chlorophenylalanine. These results suggest that the dopaminergic system has an important role in the regulation to the thiamine deficiency-induced muricide response.

Noradrenergic and dopaminergic effects of nomifensine in healthy volunteers

Intravenous doses (100 mg in 20 minutes) of the antidepressant drug nomifensine, administered to male volunteers, increased heart rate and blood pressure, elevated the plasma levels of norepinephrine and its metabolite 3-methoxy-4-hydroxyphenylglycol (MHPG), and powerfully stimulated growth hormone release and inhibited the secretion of prolactin. Oral nomifensine, either as a single 100 mg dose or as a similar dose after 2 weeks' treatment with the drug (150 mg/day), caused none of the above effects. This was in line with the limited (less than 30%) oral bioavailability of the active, unconjugated form of the drug, estimated in the same subjects. MHPG in plasma was slightly but consistently reduced by the 2 weeks' treatment, suggesting reduced turnover of norepinephrine. The observed clinical effects of nomifensine are compatible with uptake inhibition and augmented release of norepinephrine and dopamine and possibly direct agonistic effects on dopamine receptors. Although nomifensine was withdrawn from the market because of immunologic complications, it serves as a model compound of a new pharmacologic class of antidepressants, devoid of many of the disturbing side effects of the tricyclic drugs.

Disposition of nomifensine after acute and prolonged dosing

The pharmacokinetics of nomifensine were studied after single oral and intravenous doses. The effect of prolonged oral dosing on the pharmacokinetics of nomifensine was also evaluated. Nomifensine was rapidly absorbed from the gastrointestinal tract. The peak concentration of free nomifensine (0.18 mumol/L) was reached at 1.13 hours after dosing. The highest concentration after the intravenous dose was 1.21 mumol/L. The elimination t1/2 after a single dose was about 4 hours regardless of the route of administration. Nomifensine was extensively distributed in body fluids and tissues, with an apparent volume of distribution of 8.69 L/kg. The AUC of free nomifensine after oral dosing was only 26.5% of that after intravenous infusion. Absorption from the gastrointestinal tract was complete, and the AUCs of total nomifensine were equal after all treatments. The main reason for limited bioavailability seems to be extensive first-pass metabolism during the absorption process. The AUC of free nomifensine decreased substantially (from 0.78 to 0.32 hr X mumol/L) and the elimination t1/2 was shortened (from 4.39 to 2.11 hours) after a 2-week dosing period. These effects suggest marked induction of the metabolizing enzymes. An increase in nomifensine dosage may be needed in some patients to maintain a full therapeutic effect.

Metabolism of nomifensine after oral and intravenous administration

The metabolism of nomifensine was studied after single oral and intravenous administration and after 2 weeks of oral dosing. The three principal metabolites reached maximum plasma concentrations rapidly (in 1 to 1.5 hours) after nomifensine administration. Less than 10% was detected as a free, unconjugated form. All three metabolites were eliminated rapidly (elimination t1/2 values between 6.8 and 9.0 hours). Only very low concentrations of free metabolites were found in plasma after 24 hours of nomifensine administration. AUC values for free metabolites were between 0.27 to 0.46 hr X mumol/L after all nomifensine schedules. Two weeks of dosing had no significant influence on the elimination t1/2 or AUC values of the metabolites, indicating no change in the hydroxylation and methylation reactions. In addition, there were no changes in the conjugation reactions during prolonged nomifensine dosing. Nomifensine has a very short t1/2 and no tendency for accumulation after repeated doses. We conclude that nomifensine's clinical pharmacokinetic profile is not significantly changed by the kinetic behavior of its three main metabolites after the usual maintenance doses.

Influence of estrogen levels on anticholinergic activity of tricyclic antidepressives

Anticholinergic activity of a number of tricyclic antidepressives and nomifensine was demonstrated and their order of affinity for the cholinergic receptors of rat jejunum was determined. The influence of ethinyl estradiol and a conjugated estrogen product, Premarin on the binding of several tricyclic antidepressives to the hepatic mixed function oxidase system was investigated. The influence of these steroids on the metabolism of the antidepressives was evaluated and ethinyl estradiol was shown to have a marked influence on the metabolism of the antidepressives studied, while conjugated estrogens were shown to have little effect.

The treatment of depression in patients with epilepsy. A double-blind trial

Forty-two patients with depression and epilepsy were entered into an antidepressant trial of amitriptyline, nomifensine and placebo. The dose of the active drug was 25 mg tid, which was doubled in non-responders on the active drug after 6 weeks. At that point a further 6 week follow-up was carried out. Serum antidepressant and anticonvulsant levels were assessed. The results indicated that at 6 weeks all patients showed a decline in their depression scores but at 12 weeks nomifensine was superior to amitriptyline. The possible reasons for this and the clinical implications of this are discussed.

Mianserin is better tolerated and more effective in depression than a nomifensine-clobazam combination: a double-blind study

Patients suffering from depression (mostly depressive neurosis) were admitted to a double-blind study which compared the efficacy of a combination of nomifensine and clobazam with mianserin. Therapeutic efficacy was evaluated on the Hamilton Depression Rating Scale, Hamilton Anxiety Rating Scale, Clinical Global Impression Scale, physician's assessments, Global Improvement and Treatment Emergent Symptom Scale for side-effects. Assessments were made before admission to the trial and on days 3, 7, 14 and 21. Forty patients were randomly allocated to two treatment groups. A case is made against polypharmacy and in particular against the use of benzodiazepine combinations in depression. Nineteen patients on nomifensine-clobazam and 14 on mianserin completed the three-week trial. At 7, 14 and 21 days, the Hamilton Depression Rating Scale (HDRS) total scores were significantly improved for mianserin when compared with nomifensine-clobazam. Similarly, at 7 and 14 days the Hamilton Anxiety Rating Scale (HARS) total scores were significantly better for mianserin than for the nomifensine-clobazam combination. There were also significant improvements for mianserin on the HDRS sub-scales of anxiety somatization, cognitive disturbance and sleep disturbance. There were no significant differences for HDRS somatic symptoms between treatment groups. Drowsiness was the most common side-effect in both groups. The incidence of total side-effects was 74% for nomifensine-clobazam and 71% for the mianserin group.

Multicenter double-blind comparison of nomifensine and imipramine for efficacy and safety in depressed outpatients

Nomifensine, a tetrahydroisoquinoline antidepressant, was compared with imipramine in a 4-week multicenter double-blind study of depressed outpatients (100 on nomifensine, 56 on imipramine). Nomifensine was at least as effective as imipramine in reducing depressive symptoms at average doses of 150 mg/day. When significant differences did occur on Hamilton Depression Rating Scale scores, they favored nomifensine for improvement in cognitive symptoms and interest in work and activities. Early in treatment, nomifensine patients also showed a better relationship between clinical response and side effects. The proportions of patients experiencing at least one side effect or dropping out due to side effects were almost twice as high in the imipramine group. Dry mouth and sedating effects were 2-3 times more frequent among imipramine patients. Thus, nomifensine demonstrated clinical efficacy at least comparable with imipramine but with indications of a more favorable side effects profile.

The pharmacokinetics and bioavailability of nomifensine maleate in healthy men

Two studies were conducted in normal male volunteers to establish the pharmacokinetic parameters for nomifensine maleate and to determine the bioavailability of the drug from the Merital capsule intended for U.S. marketing. Single oral doses of 25, 100, and 200 mg of nomifensine maleate as aqueous solutions were administered to 24 men in the open-label Latin-square design pharmacokinetic study. In the bioavailability study, 24 men received single oral 50 mg doses of nomifensine maleate in a capsule or as an aqueous solution. Plasma levels of nomifensine were determined by radioimmunoassay and urinary levels of total nomifensine and its metabolites were assayed by thin-layer chromatography. There was a proportional increase in the area under the curve (AUC) with increasing dose, while peak plasma levels and amounts of total nomifensine and its metabolites excreted in the urine rose as dose increased. The pharmacokinetics of nomifensine are considered linear over the dose range tested. Nomifensine maleate was equally bioavailable from the 50 mg aqueous solution and the Merital capsule formulation.

Pharmacodynamics of nomifensine: a review of studies in healthy subjects

A review of pharmacodynamic studies of nomifensine in healthy subjects indicates that nomifensine caused neither negative nor positive (euphoric) mood alterations and led to no impairments in various tests of performance and to some improvement in vigilance, attention, and psychomotor performance. Nomifensine was shown to alter the waking EEG in a manner similar to desimipramine. In marked contrast to nomifensine's pharmcokinetics, its CNS effects were shown to reach a maximum after 6 hours and to last for more than 8 hours. The sleep EEG was not altered significantly. Biochemical models confirmed nomifensine's noradrenergic and dopaminergic mode of action.

A double-blind comparative evaluation of the efficacy and safety of nomifensine, imipramine, and placebo in depressed geriatric outpatients

Nomifensine, imipramine, and placebo were compared in 61 depressed geriatric outpatients over a 35-day period. At average daily doses of 150 mg, nomifensine and imipramine were significantly more effective than placebo in reducing symptoms of depression in this sample of elderly depressed patients. Nomifensine and imipramine were generally comparable in clinical effect; 78% of the nomifensine-treated patients were rated as improved at the end of treatment as compared with 64% of imipramine and 20% of placebo patients. The findings suggest a more favorable side effect profile for nomifensine, which was associated with a lower frequency of sedating and anticholinergic effects than was seen in the imipramine group.

Double-blind placebo-controlled multicenter evaluation of the efficacy and safety of nomifensine in depressed outpatients

Outpatients with primary affective disorder-depression who scored at least 20 on the Hamilton Depression Rating Scale (HDRS) were randomly assigned to treatment for 1 month with nomifensine (100-200 mg/day) or placebo. Clinical laboratory and physical evaluations, including ECGs when feasible, revealed no clinically significant changes over the course of treatment. Nomifensine patients showed improvement compared to placebo on the HDRS total score endpoint analysis (p = .06) and the Cognitive Disturbance and Retardation factors (p less than or equal to .05). A better rate of improvement was seen with nomifensine on the Clinical Global Impressions severity of illness (p less than or equal to .05) and therapeutic index (p less than or equal to .05) components. No differences were seen between groups in the incidence of overall or specific side effects. Nomifensine thus appeared safe and superior to placebo on several key measures of depressive symptomatology in this multicenter study of depressed outpatients.

Pooling 12 nomifensine studies for efficacy generalizability

Twelve parallel group, randomized, double-blind studies of nomifensine's safety and efficacy in the treatment of depressed patients were combined into three pools according to common protocols. This approach permitted evaluation of 1) efficacy results for studies with moderate-sized pools of patients, 2) the degree to which efficacy was generalizable to depressed patients in the general population, and 3) the conditions under which pooled active vs. active (imipramine vs. nomifensine) studies could be regarded as pivotal in support of efficacy. Results showed that nomifensine's superiority over placebo was generalizable to patients with a wide range of characteristics, including age 60 years or older. An appropriate statistical profile of more pronounced nomifensine responders would include patients with a duration of present episode less than 4 months who are acutely depressed, exhibit more severe symptoms, and have been previously hospitalized or treated with other psychotropic medications. A comprehensive assessment and power analysis of the pooled active vs. active studies provided strong evidence for comparability of nomifensine and imipramine.

Nomifensine in geriatric inpatients: a placebo-controlled study

In a double-blind randomized group design, nomifensine (100 mg single daily dose) was compared to placebo in 100 geriatric inpatients (average age = 75 years). Patients in each group were categorized as depressed (Feighner criteria for primary depressive disorder and Hamilton Depression Rating Scale scores greater than or equal to 18) or non-depressed (no psychopathologic disorders and HDRS scores less than or equal to 7). Outcome measures included the HDRS and various tests of cognitive function. The nomifensine-treated depressed patients showed significant improvement over the placebo depressed patients early in and throughout treatment. Depressed patients also showed significant improvement on several cognitive tests with nomifensine treatment. Nomifensine was well tolerated in both depressed and nondepressed patients.

Double-blind comparison of the efficacy and safety of nomifensine maleate vs. placebo in depressed outpatients

Nomifensine maleate in doses of 100-200 mg/day was compared to placebo in a double-blind study of 50 moderately to severely depressed outpatients seen in a private practice. Efficacy ratings over the 28-day treatment period revealed significant improvement in the nomifensine group on the Hamilton Depression Rating Scale and Clinical Global Impressions, as well as the Self-Rating Symptom Scale, Brief Psychiatric Rating Scale, and Hamilton Anxiety Scale. These differences in favor of nomifensine were seen as early as Day 7 of treatment and were generally consistent throughout the trial. No clinically meaningful changes in vital signs or laboratory values were found over the course of treatment. Only one side effect, a pruritic rash in one patient, was directly attributable to active drug treatment. The CGI Therapeutic Index revealed a very favorable ratio of clinical benefit to side effects for nomifensine maleate.

Neurotensin affects hyperactivity but not stereotypy induced by pre and post synaptic dopaminergic stimulation

The effects of intraventricular administration of neurotensin (0.9, 3.75 and 15.0 micrograms) on hyperactivity and stereotypy induced by either amphetamine (1 mg/kg), nomifensine (20 mg/kg), apomorphine (0.5 mg/kg) or N-n-propylnorapomorphine (0.5 mg/kg) were examined. Results indicate that for each drug treatment, the effects of neurotensin were identical: hyperactivity was significantly reduced while stereotypy remained unaffected. Results also revealed that neurotensin significantly increased the hypothermia induced by apomorphine and N-n-propylnorapomorphine. Possible mechanisms which could underly neurotensin's selective inhibitory action on hyperactivity produced by both pre and post synaptic dopaminergic stimulation are discussed.

Intravenous self-administration of nomifensine in rats: implications for abuse potential in humans

Rats acquired and maintained intravenous self-administration of nomifensine, a new antidepressant compound. Additional experiments implicated dopamine-containing neurons in this behavior. These findings, along with the marked pharmacological similarities between nomifensine and such drugs as cocaine and methylphenidate, indicate a potential for nomifensine abuse by humans.

[Prediction test of nomifensine prescription from symptomatic pre-therapeutic status (author's transl)]

Heighty two outpatients, suffering from reactive or neurotic depression have been treated with a daily 100 mg dose of nomifensine. The symptomatic status before treatment was appreciated by a self-rating scale, the Hopkins Symptoms Check List (HSCL). At the end of the study, the patient again filled out this same rating scale, and also a seven-score amelioration questionnaire. The investigator filled out this same questionnaire and a fourscore global impression scale. We tried to find out if by appreciating initial symptoms with the HSCL, it was possible to predict which patients would be responders to the treatment. The only highly significant result was obtained with a discriminant analysis, which combines 22 items of the pre-therapeutic HSCL and with which it is possible to predict the amelioration measured by the difference between the total pre- and post-therapeutic HSCL notations. The authors point out to the interest of this method in psychopharmacology.

[Nomifensine: clinical data (author's transl)]

Open studies with nomifensine the placebo, and double-blind controlled comparisons of nomifensine with placebo, imipramine, amitriptyline, nortriptyline... have been carried out in various parts of the world. Daily dosage varied (50-225 mg), lenght of treatment also (226 weeks). These trials showed considerable effectiveness of nomifensine in neurotic and reactive depressions, it counteracts inhibition and restores drive. Nomifensine caused no significant cardiovascular or anticholinergic side-effects. It does not potentiate the effect of alcohol.

[A double-blind nomifensine-nortriptyline trial in ambulatory patients conducted by psychiatrists in private practice: results and comments]

Nomifensine and nortriptyline were compared in a collaborative trial by psychiatrists in private practice. The trial impiled:--selection of ambulatory depressed patients--randomization in parallel groups (respectively 31 and 34 subjects)--administration in double-blind condition of 4 capsuels daily of either compound during 4 weeks--quotation of depressvie syndrom with Hamilton depression scale before treatment after 2 and 4 weeks. The analysis of results shows clear improvment of depression scores, equivalent in both groups (non significant difference and posterior rejection of an alternative hypothesis). Practical problems encountered in controlled trials in psychiatrist's outpatients are discussed.