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The effects of traditional tonics on fatigue in mice differ from those of the antidepressant imipramine: a pharmacological and behavioral study.

The present studies were undertaken to investigate the differences between the antidepressant drug, imipramine, and liquid nutritive and tonic drugs (NTDs) that consist of Ginseng radix, Epimedii herba, Holen and an additional eight to twelve crude drugs. After preloading forced swimming, the NTD (applied orally, 0.1 ml/10 g) significantly increased the duration time of swimming and decreased the duration time of immobility, while the administration of imipramine (5, 10 and 20 mg/kg, i.p.) under the same conditions and after the same treatment did not produce these positive effects. After pretreatment with 100 mg/kg tetrabenazine, the NTDs also elicited both the increased locomotor activity and the decreased duration time of immobility. The behavioral effect was similar to treatment with imipramine. The NTDs showed a long lasting effect on swimming behavior in the forced swimming test for 15 min, indicating a prolonged efficacy, not like the short effect of imipramine. The present results indicate that the effect of NTDs on fatigued subjects is different from that of imipramine, probably due to involvement of another factor in addition to the antidepressant effect.

Animals↗

Functional effects of imipramine on the rabbit urinary bladder: an in-vitro study.

Imipramine is a tricyclic antidepressant that has been demonstrated to be useful in the treatment of certain voiding dysfunctions. Imipramine has a variety of pharmacological effects including direct antimuscarinic activity, inhibition of catecholamine reuptake, direct muscle relaxant, and calcium antagonism. Using the in-vitro whole bladder model we have studied the effect of imipramine on the rate and magnitude of both intravesical pressure generation and bladder emptying in response to field stimulation. The results can be summarized as follows: at concentrations as low as 1 mumol/l imipramine causes a significant inhibition of volume expulsion without significantly affecting pressure generation. Imipramine produced a dose-dependent inhibition of both pressure development and percent volume emptying; however, it was substantially more potent in inhibiting the ability of the bladder to empty than to generate pressure.

Animals↗

The electrocardiographic and antiarrhythmic effects of imipramine hydrochloride at therapeutic plasma concentrations.

The electrocardiographic effects of imipramine hydrochloride at therapeutic plasma concentrations were determined in 44 depressed patients during a 6-week clinical outcome study of depression. During each week of the protocol, i.e., 2 weeks of control and 4 weeks of drug treatment, a standard 12-lead ECG, high-speed, high-fidelity ECG tracings, and a 24-hour continuous ECG recording were obtained. PR, QRS, and QTc intervals, T-wave amplitude, heart rate and frequency of ventricular premature depolarizations (VPDs) were measured. The plasma concentration of imipramine and desmethylimipramine was measured three times a week. Imipramine prolonged the PR (p less than 0.001), QRS (p less than 0.001) and QTc (p less than 0.001) intervals, increased the heart rate (p less than 0.001) and lowered T-wave amplitude (p less than 0.05) during the 4 weeks of treatment. No patient developed high-grade atrioventricular block or severe intraventricular conduction abnormalities. In addition, imipramine had a potent antiarrhythmic action in patients who were recovering from depression. Ten of 11 patients who had more than 10 VPDs/hour had 90% or greater arrhythmia suppression during antidepressant treatment with imipramine at plasma concentrations ranging from 100--302 ng/ml.

Adult↗

Protective effects of imipramine maintenance treatment in panic disorder with agoraphobia.

OBJECTIVE: This study was designed to assess and compare the differential relapse rates of patients with panic disorder and agoraphobia after discontinuation of acute treatment (6 months) or acute plus maintenance treatment (18 months) with imipramine. METHOD: Sixteen patients with panic disorder and agoraphobia who had shown marked and stable response to 6 months of acute imipramine treatment and a comparable group of 14 patients who had been in remission during an additional year of half-dose imipramine maintenance treatment entered a 3-month, double-blind discontinuation study followed by a 3-month drug-free period. Assessments of the patients were made according to operationalized response/relapse criteria, and plasma drug concentrations were monitored. RESULTS: Survival analysis revealed significantly different cumulative probabilities of continued response 6 months after discontinuation of imipramine treatment between the patients who had received only acute treatment and those who had received acute and maintenance treatment. CONCLUSIONS: The results support the hypothesis that successful imipramine maintenance treatment of patients with panic and agoraphobia can have protective effects against relapse, at least in the first 6 months after the maintenance treatment period.

Adult↗

Adrenoceptor mechanisms underlying imipramine-induced memory deficits in rats.

The post-training administration of tricyclic antidepressant imipramine impairs memory consolidation in the passive avoidance task. The present study investigated the effects of intrahippocampal (i.h.) injection of adrenoceptor agents on imipramine-induced (2-8 microg/rat) amnesia. The administration of the alpha1-adrenoceptor agonist phenylephrine (0.05 microg/rat) and the alpha1-adrenceptor antagonist prazosin (0.5 microg/rat) did not alter the effect of imipramine. The lower doses of phenylephrine (0.005 and 0.015 microg/rat) impaired, while the higher dose of the drug (0.025 and 0.05 microg/rat) improved retention. The effect of phenylephrine was not altered by prazosin (0.5 and 1 microg/rat) pretreatment, although prazosin alone decreased retention latencies. The alpha2-adrenoceptor antagonist yohimbine (0.5 and 1 microg/rat) decreased the response induced by imipramine. However, the alpha2-adrenoceptor agonist clonidine (0.08 microg/rat) did not alter the effect of the drug. Clonidine (0.15 and 0.3 microg/rat) by itself decreased, while yohimbine (1 and 2 microg/rat) increased retention latencies. Yohimbine pretreatment attenuated the effect of clonidine. It is concluded that alpha2-adrenoceptor mechanism(s) may be involved in imipramine-induced impairment of memory.

Adrenergic Uptake Inhibitors↗

Direct cost of depression: analysis of treatment costs of paroxetine versus Imipramine in Canada.

OBJECTIVE: To assess the potential economic impact of new and more expensive antidepressants on the overall cost of treatment using cost-effectiveness analysis. METHOD: For this analysis, a computerized decision tree of clinical practice was developed to model the 12-month treatment of moderate to severe depression in Canada. To complete the model, data were obtained from physician panels, the Ontario Ministry of Health, and clinical comparative trials of paroxetine, a selective serotonin reuptake inhibitor, and imipramine, a tricyclic antidepressant. RESULTS: The overall cost of treatment when paroxetine 30 mg per day was used first-line was found to be lower than when generic imipramine was used as the initial therapy ($1697 versus $1793). The higher drug cost of paroxetine ($1.69 per day) versus imipramine ($0.05 per day) was offset by a higher rate of treatment failures with the tricyclic necessitating an alternate therapy, additional physician visits and/or hospitalization. Sensitivity analysis of key variables determined that drug price and relapse rates after discontinuation were relatively insensitive predictors of the overall cost of care. More important was the continuation rate while on different therapies. CONCLUSION: Paroxetine demonstrated a cost-benefit relative to imipramine when the continuation rate was > or = 47%. Clinical trials of paroxetine have reported continuation rates of 41% to 65%, suggesting that paroxetine is a cost-effective alternative to imipramine in the 1-year management of patients with moderate to severe depression.

Adolescent↗

Economic analysis of treating depression with nefazodone v. imipramine.

BACKGROUND: It is estimated that treating diagnosed depression costs 420 pounds million annually in England and Wales. This economic study analyses treatment of major depression with nefazodone v. imipramine. METHOD: The study updates a previously published model using data obtained from the continuation phase of a double-blind one-year placebo-controlled comparison of nefazodone with imipramine. RESULTS: Annual costs for nefazodone are lower than those for imipramine, 218 pounds compared to 254 pounds; the cost per successfully treated patient is also lower for nefazodone than for imipramine, 242 pounds v. 323 pounds. Varying the resources included in the treatment patterns still results in lower costs for nefazodone treatment. CONCLUSIONS: Based on clinical trial data for patients completing six to eight weeks of depression treatment and followed for at least one year, the model shows that the annual costs of nefazodone are lower than those for the less expensive imipramine.

Antidepressive Agents, Second-Generation↗

Binding of H3-imipramine, H3-dimetacrine and S35-chlorpromazine to synaptosomes.

Binding of H3-imipramine, H3-dimetacrine and S35-chlorpromazine to synaptosomes of rat cerebral cortex was studied using a centrifugation method, and kinetic analysis of the experimental data. Three psychotropic drugs were shown to be rapidly bound to synaptosomes at 2 degrees C, representing a typical binding mode with two classes of binding components, i.e., saturable and non-saturable binding. A double reciprocal plot of the saturable binding component of these drugs revealed that H3-dimetacrine and S35-chlorpromazine represented a single binding mode, whereas H3-imipramine showed a multiple one. When the synaptosomes were treated by freezing and thawing 15 times, a high affinity binding component of H3-imipramine was not observed, while the other two drugs showed a single binding mode as well as those of the undisrupted synaptosomes. To investigate the specificity of this multiple binding mode, comparative binding studies of H3-imipramine were carried out using myelin fragments of rat cerebral cortex. In the myelin fragments preparation, two typical classes of binding mode as shown in the synaptosomes were also recognized. However, a double reciprocal plot of the saturable binding component showed only a straight line, i.e., single binding mode. These findings suggest that imipramine has multiple binding sites to synaptosomes and a high affinity binding component is affected by freezing and thawing procedure.

Acridines↗

Effect of imipramine on central 5-hydroxytryptamine turnover and metabolism in rats.

The levels of [3H]-5-HT and [3H]-5-HIAA in P2-fraction from rats treated with a single dose of imipramine were lower at 2, 5 and 10 min after intraventricular administration of [3H]-5-HT, compared with control animals, though these levels were statistically insignificant. Thereafter, however, the values became higher than in the controls. After long-term administration of imipramine, the levels of [3H]-5-HT and [3H]-5-HIAA in P2-fraction were, at any time after intraventricular administration of [3H]-5-HT, significantly lower than those in the fraction from controls. The endogenous contents of tryptophan and 5-HIAA were not altered either with a single dose or by long-term administration of imipramine, however, the content of endogenous 5-HT was decreased by long-term administration of imipramine. These results indicate that the rate of disappearance of 5-HT from presynaptic neurons was accelerated by long-term administration of imipramine.

Animals↗

Influence of chronic treatment with imipramine on mRNA levels in rat brain: elevation of glyceraldehyde-3-phosphate dehydrogenase levels.

The differential display method was used to identify the intrinsic factor that changes its mRNA expression level in rat brain after a 14-day oral administration of 20 mg/kg imipramine. The expression of a 180-bp band was markedly enhanced by imipramine. The results of sequencing and a data base search revealed that the isolated clone was glyceraldehyde-3-phosphate dehydrogenase (GAPDH) with a one-base difference. Enhancement of the expression by imipramine was observed in the amygdala. Quantitative PCR showed that imipramine treatment significantly elevated the GAPDH/beta-actin ratio in the cortex. These findings suggest that long-term treatment with imipramine stimulates GAPDH mRNA expression.

Adrenergic Uptake Inhibitors↗

Antinociception induced by amitriptyline and imipramine is mediated by alpha2A-adrenoceptors.

The involvement of alpha2-adrenoceptors in the antinociception induced by the tricyclic antidepressants amitriptyline and imipramine was investigated in mice by using the hot-plate and abdominal constriction tests. The antinociception produced by amitriptyline (15 mg/kg, i.p.) and imipramine (15 mg/kg, i.p.) was prevented by reserpine (2 mg/kg, i.p.) and yohimbine (3-10 mg/kg, i.p.) but not by naloxone (1 mg/kg, i.p.), atropine (5 mg/kg, i.p.), CGP 35348 (100 mg/kg, i.p.) and prazosin (1 mg/kg, i.p.). On the basis of the above data, it can be postulated that amitriptyline and imipramine exerted their antinociceptive effect by activation of alpha2-adrenoceptors. Administration of the alpha2A-adrenoceptor antagonist BRL 44408 (1 mg/kg, i.p.) prevented amitriptyline and imipramine antinociception, whereas the alpha2B/C-adrenoceptor antagonist ARC 239 (10 mg/kg, i.p.) was ineffective. These data indicate that the enhancement of the pain threshold produced by amitriptyline and imipramine is mediated by activation of alpha2A-adrenoceptors. Neither tricyclic antidepressants nor the antagonists used impaired mouse performance evaluated by the rota-rod and hole-board tests.

Amitriptyline↗

[Chronobiological research on antidepressant drugs: the effect of the antidepressant drugs, trazodone and imipramine on the circadian rhythm using electroencephalography in healthy volunteers].

The effects of the antidepressant drugs trazodone and imipramine on the circadian rhythm were studied by means of the sleep propensity test (SPT; sleep latency was examined by 35-minute EEG records at 09:00, 11:00, 13:00, 15:00, 17:00). The subjects were 11 healthy male volunteers (mean age, 23.6 years old). The drugs were administered 4 times a day with single blind trials using an inactive placebo as a control. The dosages of the drugs were trazodone 50-100 mg/day and imipramine 20-40 mg/day. We discussed the circadian rhythm referring to previous polysomnograhy (PSG) studies using the same drugs and dosages with most of the same subjects. As a result, the mean sleep latency of SPT was the shortest at 09:00 (p<0.1) with a placebo, at 11:00 (p<0.05) with trazodone and at 13: 00 (not significantly) with imipramine administration. These results suggested that neither drug affected sleepiness. They affected the circadian rhythm during the daytime (=the day rhythm). They delayed the day rhythm. Delay of the day rhythm was due to trazodone and have been caused by not only trazodon administration itself, but also by the increase of slow-wave sleep obtained in the previous night's PSG study. And the day-rhythm delay was due to imipramine and might have been caused by not only imipramine administration itself, but also by the decrease in the percentage of slow-wave sleep and REM sleep, and an increase in REM latency obtained in the previous night's PSG study. Therefore, we concluded that neither drug affected the tendency toward sleepiness, but did affect the day rhythm in healthy subjects.

Adult↗

Imipramine for the treatment of cocaine and methamphetamine dependence.

At the Drug Detoxification, Rehabilitation, and Aftercare Program of the Haight-Ashbury Free Clinics, we conducted a double-blind, controlled, randomized clinical trial of imipramine in the treatment of cocaine and methamphetamine abusers. The purpose of the trial was to test the efficacy of imipramine as a treatment for stimulant dependence and to establish the feasibility of conducting a controlled clinical trial at the clinic under conditions that approximated usual clinical practice. Subjects were randomly assigned to receive either 10 or 150 mg/day of imipramine. Imipramine 10 mg/day was the control condition. Subjects could receive study medication for up to 180 days. One-hundred eighty-three subjects participated in the study: 151 were cocaine dependent and 32 were methamphetamine dependent. In addition to receiving study medication, all subjects were assigned to intensive drug abuse counseling, which included an HIV education component. Using an intention-to-treat analysis, we found that retention in treatment was significantly longer for subjects who were treated with 150 mg of imipramine compared to control. However, we found no consistent differences between the two groups of subjects in Beck Depression Inventory scores, stimulant craving, self-report of time since last use of stimulants, or percent of urinalyses positive for stimulants. The feasibility of conducting a controlled, randomized clinical trial of medication for treatment of drug abuse was established for this community clinic setting.

Cocaine↗

Imipramine-associated hyperpigmentation.

OBJECTIVE: To inform clinicians of the potential for severe and persistent facial hyperpigmentation with the long-term use of imipramine. CASE SUMMARY: A 65-year-old white male veteran with a history of paranoid schizophrenia was referred to the psychiatry service by a dentist who thought that the patient was both cyanotic and psychotic. The history and biopsy results indicated the possibility of imipramine-associated hyperpigmentation, only the second reported case in a male patient. The presentation was complex, with a history of neuroleptic exposure and multiple signs of parkinsonism. A brain single photon-emission computed tomography scan demonstrated frontal lobe hypermetabolism and bilateral caudate hypermetabolism, which normalized 14 months later. Despite discontinuation of imipramine, the patient continued to appear cyanotic, leading to worsening social isolation. He became known as "the man with the purple face." On his rare ventures outside the home, he was embarrassed by sporadic calls to 911 by persons fearing he was ill. DISCUSSION: Although facial hyperpigmentation secondary to the use of phenothiazines has been reported frequently, it is much less common with imipramine, and is very rare in males. Failure to recognize this adverse reaction led to continuing treatment with imipramine and to an apparently irreversible condition. The brain imaging findings have no link with the hyperpigmenting process, but raise questions about neuroleptic-induced metabolic changes in the brain. CONCLUSIONS: Clinicians need to be aware of rare adverse reactions such as hyperpigmentation, and be prepared to take appropriate and early action to prevent such reactions from becoming irreversible.

Aged↗

Serotonin (5HT), fluoxetine, imipramine and dopamine target distinct 5HT receptor signaling to modulate Caenorhabditis elegans egg-laying behavior.

Drugs that target the serotonergic system are the most commonly prescribed therapeutic agents and are used for treatment of a wide range of behavioral and neurological disorders. However, the mechanism of the drug action remain a conjecture. Here, we dissect the genetic targets of serotonin (5HT), the selective 5HT reuptake inhibitor (SSRI) fluoxetine (Prozac), the tricyclic antidepressant imipramine, and dopamine. Using the well-established serotonergic response in C. elegans egg-laying behavior as a paradigm, we show that action of fluoxetine and imipramine at the 5HT reuptake transporter (SERT) and at 5HT receptors are separable mechanisms. Even mutants completely lacking 5HT or SERT can partially respond to fluoxetine and imipramine. Furthermore, distinct mechanisms for each drug can be recognized to mediate these responses. Deletion of SER-1, a 5HT1 receptor, abolishes the response to 5HT but has only a minor effect on the response to imipramine and no effect on the response to fluoxetine. In contrast, deletion of SER-4, a 5HT2 receptor, confers significant resistance to imipramine while leaving the responses to 5HT or fluoxetine intact. Further, fluoxetine can stimulate egg laying via the Gq protein EGL-30, independent of SER-1, SER-4, or 5HT. We also show that dopamine antagonizes the 5HT action via the 5HT-gated ion channel MOD-1 signaling, suggesting that this channel activity couples 5HT and dopamine signaling. These results suggest that the actions of these drugs at specific receptor subtypes could determine their therapeutic efficacy. SSRIs and tricyclic antidepressants may regulate 5HT outputs independently of synaptic levels of 5HT.

Animals↗

Influence of imipramine on the duration of immobility in chronic forced-swim-stressed rats.

We studied the influence of imipramine on the duration of immobility in chronic forced-swim-stressed rats. Both single and chronic administration of imipramine potently shortened immobility in naive rats during forced-swim testing. However, chronic, 14-day forced-swim stress testing blocked the immobility-decreasing effect induced by a single administration of imipramine. When imipramine was administered for 14 days concurrently with forced-swim stress testing, immobility was shortened significantly. From the viewpoint of imipramine's effect, these findings suggest that chronic forced-swim stress testing in rats may be an effective animal model for depression.

Animals↗

Clinical pharmacokinetics of imipramine and desipramine.

The pharmacokinetics of imipramine and desipramine have been extensively investigated with recent studies designed to understand sources of intersubject variability and to study discrete clinical populations rather than healthy volunteers. Sources of intersubject variability in pharmacokinetics are both genetic (oxidative phenotype) and environmental. Oxidative phenotype has an important impact on first-pass metabolism. In individuals with poor metabolism, systemic availability for imipramine is increased. Intrinsic clearance of desipramine is reduced 4-fold in individuals with poor metabolism. Recent pharmacokinetic studies in diverse patient populations such as the depressed elderly, children and alcoholics have revealed decreased clearance of imipramine in the elderly and increased clearance of both imipramine and desipramine in chronic alcoholics. In at least a third of the population, nonlinear pharmacokinetics of desipramine may be observed at steady-state plasma concentrations above 150 micrograms/L. These nonlinear changes in desipramine pharmacokinetics are not associated with age or sex, but are associated with higher desipramine 2-hydroxydesipramine concentration ratios. Hydroxylated metabolites of imipramine and desipramine may possess both antidepressants and cardiotoxic activity but their formation is rate limited and plasma concentrations tend to follow the parent compound with little accumulation. The potent cardiovascular effects of the hydroxymetabolites may be particularly relevant for the elderly and in acute overdose.

Biological Availability↗

Analysis of imipramine and three metabolites produced by isozyme CYP2D6 expressed in a human cell line.

1. A commercially-available human cytochrome P450 isozyme (CYP2D6) preparation was used in imipramine metabolism studies. This isozyme catalysed both aromatic C-oxidation and N-demethylation. 2-Hydroxyimipramine was the major metabolite; desipramine was isolated in a significant amount and 2-hydroxydesipramine was a trace metabolite. 2. To prevent decomposition of metabolites during the analytical procedure, the metabolism mixture was derivatized with acetic anhydride prior to extraction, and the derivatized metabolites were separated and quantified by g.l.c. with N/P detection. The analytical procedure had excellent sensitivity and was capable of routinely quantifying imipramine and its metabolites down to the 0.36 nmol level. 3. In excess of 90% of drug and metabolites was consistently recovered when metabolism was conducted over a 5-60-min duration. 4. The formation of the secondary metabolite, 2-hydroxydesimipramine, from imipramine proceeds by two pathways, via desipramine and via 2-hydroxyimipramine; the former is the preferred pathway. 5. CYP2D6 catalyses C-hydroxylation of imipramine to 2-hydroxyimipramine more efficiently than its N-demethylation to desipramine. Also, the C-hydroxylation of imipramine to 2-hydroxyimipramine proceeds more efficiently than the conversion of desipramine to 2-hydroxydesipramine.

Catalysis↗