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Enhanced displacement of [3H]imipramine, but not [3H]paroxetine binding by plasma from depressed patients.

Plasma from healthy subjects inhibited the binding of [3H]imipramine competitively and [3H]paroxetine non-competitively to platelet membranes in a volume-dependent manner. Plasma from 40 depressed patients was more effective at inhibiting [3H]imipramine, but not [3H]paroxetine, binding compared to plasma from matched controls. This difference was not related to recent antidepressant treatment. The results suggest that the concentration of an endogenous modulator of [3H]imipramine binding is increased in depressive illness. The concentration of alpha 1-acid glycoprotein, a proposed endogenous modulator of [3H]imipramine binding, did not differ between depressed patients and controls. Our results suggest that factors other than alpha 1-acid glycoprotein may modulate [3H]imipramine binding.

Adult↗

S-adenosyl-L-methionine prevents 5-HT(1A) receptors up-regulation induced by acute imipramine in the frontal cortex of the rat.

S-adenosyl-L-methionine (SAM) has shown efficacy in speeding the onset of the antidepressant effect of imipramine in depressed patients. This effect may be related to their interactions at the serotonin(1A) (5-HT(1A)) receptors. Acute imipramine up-regulated the frontal cortex 5-HT(1A) receptors (B(max), 51.5 +/- 8.4 fmol/mg protein) vs. saline (B(max), 27.5 +/- 5.9 fmol/mg protein), and did not show antidepressant effect. Acute SAM and imipramine+SAM did not modify frontal cortex 5-HT(1A) receptors, and showed antidepressant effects (decrease of the immobility response of 26%, P<0.01; and 47%, P<0.001) vs. saline. All the chronic treatments showed antidepressant effects and up-regulated the hippocampus 5-HT(1A) receptors. SAM prevents the 5-HT(1A) receptor up-regulation induced by acute imipramine in the frontal cortex. This mechanism may contribute to imipramine's antidepressant effect.

Animals↗

The analgesic effect of codeine as compared to imipramine in different human experimental pain models.

The hypoalgesic effect of single oral doses of 100 mg imipramine and 125 mg codeine was evaluated in a randomised, placebo-controlled, double-blind, 3-way cross-over experiment including 18 healthy volunteers. Pain tests were performed before and 90, 180, 270, 360 and 450 min after medication. The tests included determination of pain tolerance thresholds to pressure, pain detection/tolerance thresholds to single electrical sural nerve stimulation and pain summation at tolerance threshold to repetitive electrical sural nerve stimulation (temporal summation) and pain experienced during the cold pressor test, rated as peak pain intensity, pain average intensity and discomfort. Compared to placebo, imipramine significantly increased pressure pain tolerance threshold (P = 0.03) and increased pain tolerance threshold (P = 0.05) and pain summation threshold (P = 0.03), but not pain detection threshold to electrical stimulation. Imipramine did not cause significant changes in pain perception during the cold pressor test. Codeine significantly increased pressure pain tolerance threshold (P = 0.02), pain detection (P = 0.04) and pain tolerance threshold (P = 0.01) and pain summation threshold (P = 0.02) to electrical stimulation. In addition, codeine reduced the pain experienced during the cold pressor test (P = 0.04-0.003). It is concluded that both imipramine and codeine inhibit temporal pain summation, whereas only codeine reduces cold pressor pain. Pain summation may be a key mechanism in neuropathic pain. Imipramine has a documented effect on such pain conditions on temporal summation. The present study showed that codeine also inhibits temporal summation, which is in line with the clinical observations indicating that opioids relieve neuropathic pain.

Adrenergic Uptake Inhibitors↗

A controlled trial of imipramine for the treatment of methamphetamine dependence.

At the Drug Detoxification Program of the Haight Ashbury Free Clinics, we conducted a randomized clinical trial of imipramine in the treatment of methamphetamine dependence. The purposes of the trial were to test the efficacy of imipramine as a treatment for methamphetamine dependence and to establish the feasibility of conducting a controlled clinical trial at the Clinic. Thirty-two subjects were randomly assigned to receive either 10 or 150 mg/day of imiprine for 180 days. Imipramine 10 mg/day was the control. Subjects received intensive counseling. Retention in treatment was significantly longer for subjects who were treated with 150 mg of imipramine compared to control (median days: 33.0 vs. 10.5). There were no consistent differences in percent of urine samples positive for methamphetamine, Beck Depression Inventory scores, or craving. Determination of the full extent of imipramine's utility in the treatment of methamphetamine dependence awaits a larger trial.

Adult↗

24-Hour motor activity after treatment with imipramine or fluvoxamine in major depressive disorder.

Psychomotor dysfunction in depression is related to alterations in the 24-h pattern of motor activity. After antidepressant treatment the diurnal pattern may be changed due to improvement of clinical state or pharmacological actions. The purpose of this study was to evaluate in 52 depressed in-patients the effects of imipramine (tricyclic antidepressant) and fluvoxamine (SSRI) on the 24-h motor activity. Motor activity was monitored by wrist-actigraphy during a medication-free period and after 4 weeks of treatment. Clinical improvement was not different after imipramine or fluvoxamine treatment. The Hamilton depression score decreased in patients treated with imipramine, as well as in patients treated with fluvoxamine. The clinical retardation score was also reduced in both treatment groups. However, patients treated with imipramine showed higher motor activity levels during the wake period in comparison to the medication-free period, and more fragmentation of motor activity during sleep. Treatment with fluvoxamine did not result in alterations in the 24-h pattern of motor activity. The improvement of depressive mood and retardation seems to play a minor role in the change of the pattern of motor activity after imipramine.

Adult↗

Differential effects of repeated imipramine on hippocampal responsiveness to adenosine and serotonin.

Imipramine-induced enhancement of the inhibitory action of 5-HT(lA) receptor activation in hippocampal pyramidal neurons has been attributed to alterations in the transduction mechanism that involves G protein-dependent opening of K(+) channels. Postsynaptic 5-HT(lA) and adenosine Al receptors may share that transduction pathway. We investigated the influence of repeated imipramine administration on 5-HT(lA) and adenosine A1 receptor-mediated effects in rat hippocampal slices. Repeated imipramine selectively enhanced the postsynaptic effects of 5-HT(1A) receptor activation, including hyperpolarization and reduction of input resistance of neurons and reduction of the population spike amplitude. In contrast, after imipramine treatment only the presynaptic effect of adenosine receptor agonists, a decrease of the field excitatory postsynaptic potential, was enhanced. The data demonstrate that alterations in the presumed common transduction mechanism that was postulated for the 5-HT(lA) and adenosine A1 receptor-mediated activation of K(+) channels are not involved in the effect of repeated imipramine administration.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

Adenosine receptor agonists or antagonists alter antinociception, but did not show an interaction with imipramine-induced antinociception in the formalin test in mice.

In this study, the antinociceptive effect of imipramine and adenosine agents, and interactions between imipramine with adenosine drugs in mice in the formalin test, have been investigated. Intraperitoneal administration of different doses of imipramine (10, 20, 30 and 40 mg/kg) induced a dose dependent antinociception in mice, in both the first and second phases of the formalin test. The adenosine A(1) receptor agonists, R-(N(6)-phenylisopropyl)-adenosine (0.015, 0.03 and 0.1 mg/kg) and 5'-N-ethylcarboxamide adenosine (0.001, 0.005, 0.01 mg/kg), but not 2-chloroadenosine (0.1 and 0.5 mg/kg), and the adenosine receptor antagonist, 8-phenyltheophylline (0.1, 0.5 and 1 mg/kg), but not 1,3-dipropyl-7-methyl-xanthine (0.5 and 5 mg/kg), also produced an antinociceptive response. Lower dose of the adenosine receptor antagonist theophylline induced antinociception, while a higher dose of the drug caused hyperalgesia. Theophylline reduced the response induced by imipramine. It is concluded that adenosine systems are not involved in imipramine responses in the formalin test.

2-Chloroadenosine↗

Potentiation of imipramine-induced antinociception by nicotine in the formalin test.

In this study, the effect of cholinergic agents on imipramine antinociception in mice, in the formalin test, has been investigated. Intraperitoneal (i.p.) administration of different doses of imipramine (2.5, 5, 10, 20 and 30 mg/kg) or nicotine (0.25, 0.5, 0.75 and 1 mg/kg) induced a dose dependent antinociception in both the first and second phases of the formalin test in mice. The combination of imipramine with doses of 0.5 and 0.75 mg/kg of nicotine showed a potentiated response, in both phases of the test. However, neither hexamethonium (5 and 10 mg/kg), atropine (0.25 mg/kg) or mecamylamine (0.25 mg/kg) altered the antinociception induced by imipramine. It is concluded that nicotinic receptor activation but not the cholinergic muscarinic mechanism is involved in the imipramine-induced antinociception.

Analgesics↗

Efficacy and tolerability of reboxetine compared with imipramine in a double-blind study in patients suffering from major depressive offsodes.

A 6-week, randomised, double-blind, multicentre study in 256 patients with a DSM-III-R diagnosis of major depression was carried out to compare the selective noradrenaline reuptake inhibitor (NARI), reboxetine, with the reference standard tricyclic antidepressant, imipramine. The efficacy of reboxetine, as measured by the extent of improvement of Hamilton Depression Rating Scale. Montgomery and Asberg Depression Rating Scale and the Clinical Global Impression Scale, was similar to that of imipramine. The improvement was observed in the overall population and in severely depressed and melancholic patients. Reboxetine tolerability compared favourably with that of imipramine. Frequency of discontinuation due to adverse events was lower in the reboxetine-treated group (10.0%) than in the imipramine-treated group (14.3%), and the cumulative risk of development (Kaplan-Meier analysis) of dry mouth, hypotension and/or related symptoms and tremor was significantly higher on imipramine than on reboxetine.

Adrenergic Uptake Inhibitors↗

Comparison of hypericum extracts with imipramine and fluoxetine in animal models of depression and alcoholism.

Clinical evidence suggests that hypericum extracts (Hypericum perforatum L., St. John's wort) have antidepressive properties and may offer an interesting alternative for the treatment of mood disorders. In addition, hypericum extracts, as well as standard antidepressants such as the tricyclic, impramine, and the selective serotonin reuptake inhibitor, fluoxetine, have been reported to be of therapeutic benefit in the treatment of alcoholism, as these compounds may reduce alcohol craving and/or intake in particular subgroups of patients. It was the aim of the present study to compare the effects of hypericum extracts with those of imipramine and fluoxetine in the rat forced swimming test (RFST), a model of depression, as well as in cAA rats, a genetic model of alcoholism. In the RFST, triple i.p. administration of imipramine (3-30 mg/kg) and fluoxetine (3-30 mg/kg) induced a dose-dependent reduction in immobility: the minimal effective dose (MED) being 30 and 10 mg/kg, and the maximal effect being 50% and 57% immobility reduction, for imipramine and fluoxetine, respectively. In this test, the hypericum extracts Ze 117 (Remotiv) and LI 160 (Jarsin) also induced a statistically significant reduction of immobility when administered under the same application schedule (5-40 mg/kg, i.p., triple application). In the case of the hypericum extracts the dose-response relationship was inverted U-shaped with a MED value of 20 mg/kg and a maximal effect of 41% and 32% immobility reduction, for Ze 117 and LI 160, respectively. Interestingly, the anti-immobility effects tended to be more pronounced after subacute (1 week, B.I.D.) treatment with 10 mg/kg of imipramine, fluoxetine, or Ze 117, as compared with acute treatment. This phenomenon is in accordance with clinical experience and suggests that repeated treatment is required for full development of antidepressive effects. In the alcohol-preferring cAA rats, acute i.p. administration of imipramine (3-30 mg/kg), fluoxetine (1-10 mg/kg) and Ze 117 (10-40 mg/kg) dose-dependently reduced alcohol intake in a 12-h limited access two-bottle [ethanol 10% (v/v) versus water] choice procedure: with MED values of 30, 5 and 20 mg/kg, respectively. The anti-alcohol effects of fluoxetine and Ze 1-17 appeared to be specific, as reductions in alcohol intake coincided with reductions in alcohol preference. The present study suggests that hypericum extracts have antidepressant-like properties which resemble those of clinically established antidepressants, and that Remotiv may be an interesting adjunct for the treatment of alcoholism.

Alcoholism↗

Antidepressant efficacy and safety of low-dose sertraline and standard-dose imipramine for the treatment of depression in older adults: results from a double-blind, randomized, controlled clinical trial.

This study compared the efficacy and tolerability of 150 mg/day imipramine and 50 mg/day sertraline for the treatment of a major depressive episode (DSM-IV) in older adults (N = 55) in an 8-week, randomized, double-blind, controlled clinical trial. Intention-to-treat analysis (last observation carried forwards) showed a reduction of 50% or more on the baseline scores of the Montgomery-Asberg Rating Scale (MADRS) in 60.7% and 55.6% of patients receiving imipramine and sertraline, respectively (p = .698). Full remission of symptoms (MADRS < 9) was observed in 50.0% and 51.8% of patients, respectively (p = .891). Side effects were more frequent among patients treated with imipramine (86.7%) than among patients treated with sertraline (42.1%) (p = .008). Dropout rates were high in both groups (46.4% and 29.6% respectively, p =.200). These results indicate that imipramine and sertraline are equally effective for the treatment of major depression in later life, although adverse reactions are more frequent among subjects treated with imipramine than with sertraline.

Aged↗

2nd year maintenance and discontinuation of imipramine in panic disorder with agoraphobia.

BACKGROUND: The results from our 1 year placebo-controlled maintenance/discontinuation study in remitted panic disorder with agoraphobia patients confirmed the significant prophylactic effectiveness of imipramine maintenance treatment but suggested that this may be necessary in only 37% of the patients who relapse following discontinuation of 6 months acute imipramine treatment. This paper presents pilot data from a second year extension of the above-mentioned study with the aim of exploring the putative protective effects of maintenance imipramine therapy beyond the 1st year. METHOD: Eighteen patients from the 30 who survived, in stable remission, the first 12 months of the maintenance/discontinuation study gave written consent to participate in a double-blind 2nd year extension phase with the knowledge that those on placebo will continue on the same condition (N = 7, PBO-PBO) and those on imipramine (N = 11) will be rerandomized to 2nd year maintenance (N = 4, IMI-IMI) or placebo substitution (N = 7, IMI-PBO). The procedures continued unchanged from that of the 1st year of the study and patients were followed with planned assessments every 2 months over the second 12-month experimental period of the study. RESULTS: None of the IMI-IMI patients relapsed, two (28.5%) of the IMI-PBO patients relapsed, and two (28.5%) of PBO-PBO patients relapsed. The mean estimated time without relapse was 10 months and 9 months for IMI-PBO and PBO-PBO, respectively. The estimated probability of not relapsing was .64 for IMI-PBO and .60 for PBO-PBO (Mantel-cox test chi2 =.84, p = .77). CONCLUSION: These interlocking controlled observations tentatively suggest that a substantial degree of prophylactic efficacy continues and that a substantial need for continued prophylaxis exists beyond the 1st year of maintenance imipramine treatment in panic disorder with agoraphobia patients.

Agoraphobia↗

Hemodynamic responses of trazodone and imipramine.

The hemodynamic effects of trazodone (150 mg) and imipramine (75 mg) were examined in eight healthy subjects. Trazodone significantly increased left ventricular ejection time 1 (LVETI), but decreased both preejection period (PEP) and PEP/LVET ratio. It also decreased heart rate and systolic and diastolic blood pressure at 90 min after dosing. Imipramine initially increased total electromechanical systole I (QS2I) and PEP (30 min, P less than 0.01), but at 150 and 180 min after dosing QS2I was significantly lower. Imipramine increased diastolic blood pressure at 30 min (P less than 0.05) and increased systolic blood pressure between 90 and 180 min (P less than 0.05). At 30 and 60 min heart rate was significantly depressed by imipramine. There were no significant changes in the values of stroke volume and cardiac output. These results suggest that trazodone has its major effect on the circulation through its alpha-receptor blocking activity, whereas the effects of imipramine are probably mediated through its ability to block reuptake of norepinephrine.

Adult↗

Imipramine binding to alpha-1-acid glycoprotein in normal subjects and cardiac patients.

The relationship between binding ratio of imipramine and plasma alpha 1-acid glycoprotein (AAG) was determined in normal subjects, patients with chest pain syndrome, and patients after myocardial infarction. Binding ratio of imipramine was determined by equilibrium dialysis and plasma AAG concentration was determined by radial immunodiffusion. Plasma AAG concentrations ranged from 56 to 80 mg/dl (mean = 65 +/- 9 mg/dl) in 12 normal subjects, from 86 to 228 mg/dl (mean = 125 +/- 37 mg/dl) in 12 patients with chest pain syndrome, and from 78 to 350 mg/dl (mean = 181 +/- 69 mg/dl) in 12 patients after myocardial infarction. Plasma AAG concentrations in the three patient groups differed. Binding ratio ranged from 5.6 to 19.8 (mean = 12 +/- 3.5). Binding ratio of imipramine significantly correlated with plasma AAG concentration, but not with plasma albumin. In addition, binding ratio of imipramine and pure AAG was significantly related, indicating AAG is an important determinant for imipramine binding. If plasma AAG concentration increases or changes rapidly, plasma drug concentration and drug effect may be unpredictable. Under these circumstances an estimate of free drug fraction may be clinically helpful and can be estimated from the formula. y = 7.95 + 0.03 X AAG.

Adult↗

Imipramine demethylation and hydroxylation: impact of the sparteine oxidation phenotype.

Eighteen healthy volunteers, selected according to their ability to oxidize sparteine, took single oral doses of 100 mg imipramine and desipramine. For imipramine the following clearances (L X min-1) were found in six rapid extensive metabolizers (EM), six slow EM, and six poor metabolizers (PM), respectively (mean and range): apparent oral clearance: 2.55 (1.39 to 3.47), 2.28 (1.18 to 4.26), and 1.35 (0.96 to 1.64). Clearance via demethylation was: 1.42 (0.61 to 2.01), 1.60 (0.78 to 3.81), and 1.09 (0.76 to 1.64); clearance via other pathways was: 1.13 (0.74 to 1.75), 0.69 (0.40 to 1.59), and 0.26 (0 to 0.46). For desipramine the apparent oral clearance (L X min-1) was 0.19 (0.12 to 0.24) in PM compared with 1.64 (1.46 to 1.80) and 1.03 (0.77 to 1.13) in rapid EM and slow EM. Extremely long elimination t1/2s of desipramine were seen in PM: 81 to 131 hours compared with 13 to 23 hours in EM. 2-OH-imipramine and 2-OH-desipramine were detectable in plasma of only the 12 EM, where the ratio-to-parent compound was higher in rapid EM than in slow EM. This study confirms that 2-hydroxylation of imipramine and desipramine depends almost exclusively on the sparteine oxygenase, whereas the demethylation of imipramine depends mainly on a different isozyme.

Adult↗

Concentration-response relationship in imipramine treatment of diabetic neuropathy symptoms.

A single-blind imipramine dose titration study was conducted in 15 diabetic patients with neuropathy symptoms. The effect of treatment was evaluated by use of visual analog scales. Imipramine doses were individually adjusted until doses yielded plasma concentrations of imipramine plus desipramine that were well above 400 nmol/L or until all neuropathy symptoms had vanished. In all except one patient, there was marked relief of symptoms. In the responding patients (n = 14), much of the effect occurred at plasma levels of imipramine plus desipramine below 100 nmol/L, but a considerable interindividual variation was observed. Concentrations above 400 to 500 nmol/L were required to ensure maximal effect in all patients, and we did not find any indication of a decreased effect at high drug levels. The dose-dependent kinetics of imipramine was confirmed, and dose increments should therefore be carried out in small steps and preferably with monitoring of drug levels.

Adult↗

Nicotine and nicotinic receptor antagonists potentiate the antidepressant-like effects of imipramine and citalopram.

1. Epidemiological and clinical observations suggest the involvement of nicotinic acetylcholine receptors (nAChRs) in depressive illness. Nonetheless, there is no clearcut evidence that nicotine and/or nAChR antagonists produce an antidepressant effect. 2. In the tail-suspension test (C57/Bl male mice), nicotine (0.8-1.2 mg kg(-1) s.c. or i.p.) given 15-60 min before the measurement exerted no effect on immobility. 3. Given 30 min before the measurement, citalopram (2 mg kg(-1)) produced a slight decrease in immobility; coadministration of nicotine (0.8 mg kg(-1), 15 but not 40 min before the test) to citalopram-treated mice resulted in a robust decrease in immobility. Imipramine (4 mg kg(-1)) did not affect immobility, but given in combination with 0.8 mg kg(-1) of nicotine (15 but not 40 min before the test), a decrease in immobility was observed. Nicotine (0.8 and 1.2 mg kg(-1)) also produced an enhancement in the anti-immobility effect of imipramine (20 mg kg(-1)). 4. We further investigated if nAChR antagonists would influence the antidepressant-like effects of imipramine and citalopram. Unexpectedly, mecamylamine (1-2.5 mg kg(-1)) and dihydro-beta-erythroidine (2 mg kg(-1)) potentiated the antidepressant-like effect of imipramine (4-20 mg kg(-1)). Mecamylamine (2.5 mg kg(-1)) but not dihydro-beta-erythroidine also increased the antidepressant-like effect produced by 2 mg kg(-1) of citalopram. 5. The interaction between nAChR antagonists and antidepressants appeared synergistic. 6. Neither nAChR ligands, antidepressants nor combinations of the two, affected locomotor activity. 7. The present results demonstrate an unexpected interaction between nAChR ligands and imipramine and citalopram in the tail-suspension test.

Animals↗

Cell proliferation is influenced by bulbectomy and normalized by imipramine treatment in a region-specific manner.

Growing evidence indicates that alterations of neuroplasticity may contribute to the pathophysiology of depression. In contrast, various antidepressants increase adult hippocampal neurogenesis and block the effects of stress. These findings result in the 'neurogenesis hypothesis of depression'. The present study seeks to determine out whether cell proliferation is altered in the hippocampus, subventricular zone (SVZ), and basolateral amygdala of adult rats exposed to bilateral olfactory bulbectomy, another established model of depression and, if so, how imipramine effects bulbectomy-induced changes of cell genesis. Bulbectomy results in a significant reduction of cell proliferation in the hippocampus and SVZ, an effect that is normalized by subchronic doses of imipramine. Moreover, an increase in cell genesis in the basolateral amygdala, which is not affected by imipramine, is demonstrated. TUNEL staining indicates an enhanced apoptosis after bulbectomy in the SVZ that cannot be reduced by imipramine. Cell death rates in the hippocampus and amygdala are not affected by bulbectomy. The opposing effects of bulbectomy and imipramine treatment in the hippocampus and amygdala demonstrate that these structures of the limbic system, both integrated in emotional processing, react quite differently with regard to neuroplasticity. Further to this, we discuss a possible link between the pathogenesis of depression and changed neuronal plasticity in the SVZ.

Amygdala↗