Treatment of multiple sclerosis with lofepramine, L-phenylalanine and vitamin B(12): mechanism of action and clinical importance: roles of the locus coeruleus and central noradrenergic systems

In a randomized, placebo-controlled double-blind trial a combination of lofepramine, phenylalanine and vitamin B(12) was found to be effective in relieving the symptoms of multiple sclerosis (MS). The effect occurred within 2-4 weeks, and improved all types of symptoms in all types of MS. The combination was also effective in relieving symptoms in patients with chronic pain and chronic fatigue. We hypothesize that the action of this combined therapy may relate to activation of the noradrenergic locus coeruleus/lateral tegmentum (LC/LT) system which has the potential to influence the functioning of large areas of the brain and spinal cord.

The effect of lofepramine and other related agents on the motility of Tetrahymena pyriformis

Tricyclic antidepressants (TCAs) were introduced almost 50 years ago. Whilst there is no doubt that TCAs are effective in treating depression, they are also more cardiotoxic when taken in overdose than other antidepressant groups. Lofepramine is a more recently introduced modified TCA, which in animals and man has low toxicity when compared to older TCAs. Paradoxically, lofepramine is extensively metabolised to desipramine, which has considerable toxicity, both experimentally and in overdose. The toxicity of such compounds is attributed, in part, to a membrane stabilising effect (MSA) on cell membranes. This MSA causes gross effects to the cell structure and in turn, normal cell activity. The aim of this study was to compare the MSA of lofepramine with that of desipramine and amitriptyline in order to see if this might help to explain the low toxicity of lofepramine. The local anaesthetic agent lignocaine was also studied for comparison. Each compound was enclosed in a beta-cyclodextrin to increase its solubility in aqueous medium. The extent of MSA was determined as a measure of the effect on the swimming speed of the protozoan Tetrahymena pyriformis using a video image analysis system. The IC50s for the various drugs were then correlated with their respective octanol-water partition coefficient values (Pow). Amitriptyline had an IC50 of 1.26+/-0.29 mM, desipramine 75.99+/-14.40 mM, while lofepramine had an IC50 of 357.40+/-25.00 mM. Lignocaine had an IC50 of 85.73+/-18.30 mM. There was also a significant correlation between the IC50 values and the Pow values.

An investigation of the antidepressant properties of lofepramine and its desmethylated metabolites in the forced swim and olfactory bulbectomized rat models of depression

The purpose of this study was to examine the metabolites of lofepramine (LOF), namely desipramine (DMI), desmethyl desipramine (DDMI) and desmethyl lofepramine (DML) in the forced swim and olfactory bulbectomized (OB) rat models of depression. In the first study, subacute treatment with DMI (10 mg/kg) and DML (20 mg/kg), but not LOF, reduced the immobility time in the forced swim test. In the "open field", chronic (14 day) treatment with all drugs attenuated the hyperactivity associated with olfactory bulbectomy. In the second experiment, a lower dose of DML (10 mg/kg) demonstrated activity following subacute treatment in the forced swim and following chronic treatment in the OB model. In addition, DDMI (10 mg/kg) was active in both models. From these results, it can be concluded that, at the doses employed, LOF and it's desmethylated metabolites, DMI, DML and DDMI, exhibits activity in the OB model. In contrast, lofepramine but not it's desmethylated derivatives is inactive in the forced swim test, perhaps suggesting the requirement of metabolic conversion of LOF to reveal antidepressant activity in this model.

Use of selective serotonin reuptake inhibitors and other serotonergic drugs in the biological dissection of affective disorders

The need to subtype patients with affective disorders on the basis of biological characteristics is well recognized, and much of the research in this area has focused on the serotonergic system. Biological subtyping can be approached using both peripheral and central markers. Peripheral markers include platelet serotonin concentrations, the density and affinity of platelet serotonin reuptake and platelet 5-HT2 receptors, and plasma serotonin concentrations. Central markers include cerebrospinal fluid (CSF) 5-hydroxyindoleacetic acid (5-HIAA) concentrations, and endocrine, psychological and body temperature responses to challenge tests with a number of serotonergic drugs. More recently, the role of selective serotonin reuptake inhibitors (SSRIs) and other serotonergic drugs in sleep, and in the control of cardiovascular homeostasis, has been studied. This may provide a greater understanding of the mechanisms of serotonin dysregulation in affective disorders, and may ultimately improve treatment of these conditions.

Effect of lofepramine on 5-HT function and sleep

We studied the effect of the tricyclic antidepressant lofepramine (140-210 mg daily for 16 days) on 5-hydroxytryptamine 1A (5-HT1A) receptor sensitivity in healthy volunteers, using a buspirone neuroendocrine challenge paradigm (30 mg orally). We also studied the effect of lofepramine on platelet 5-HT content and sleep architecture. Lofepramine treatment did not alter the hypothermic, endocrine or amnesic effects of buspirone but significantly lowered platelet 5-HT content and decreased rapid eye movement sleep. Our findings suggest that at clinically used doses, lofepramine inhibits the uptake of 5-HT and produces changes in sleep architecture characteristic of tricyclic antidepressants. However, lofepramine does not appear to alter the sensitivity of 5-HT1A receptors.

The effects of lofepramine and desmethylimipramine on tryptophan metabolism and disposition in the rat

Acute and chronic administration of lofepramine and its major metabolite desmethylimipramine (DMI) to rats elevates brain tryptophan concentration, thereby enhancing cerebral 5-hydroxytryptamine (5-HT) synthesis, by increasing the availability of circulating tryptophan to the brain, secondarily to inhibition of liver tryptophan pyrrolase (tryptophan 2,3-dioxygenase, L-tryptophan:O2 oxidoreductase, decyclizing; EC 1.13.11.11) activity. The pyrrolase inhibition by lofepramine occurs independently of metabolism to DMI, because it can be demonstrated directly in vitro. Lofepramine also differs from DMI in its action profile on the above and related aspects of tryptophan metabolism and disposition. These results demonstrate that lofepramine influences tryptophan and 5-HT metabolism and disposition independently of its major metabolite DMI, and are discussed briefly in relation to the mechanism of action of antidepressants.

Effects of (S)-nafenodone, a new antidepressant, in isolated guinea-pig atrial and ventricular muscle fibres

The electromechanical effects of a new antidepressant, (S)-nafenodone, were studied in isolated guinea-pig atrial and ventricular muscle fibres. In spontaneously beating right atria, (S)-nafenodone decreased the rate and amplitude of contractions and lengthened the sinus node recovery time. In electrically driven atria, the negative inotropic effect of (S)-nafenodone was less marked than that of imipramine and desipramine but similar to that of lofepramine. (S)-Nafenodone had no effect on the resting membrane potential but decreased the amplitude and maximum upstroke velocity (Vmax) both in atrial and ventricular muscle fibres; this effect was less marked than that produced by imipramine and desipramine. In atrial fibres, but not in ventricular fibres, (S)-nafenodone lengthened the action potential duration, but in both tissues it increased the duration of the effective refractory period out of proportion to the change in action potential duration. Moreover, it shifted the concentration-response curve for Ca2+ downwards and decreased the amplitude of the slow atrial contractions induced by histamine as well as the amplitude and Vmax of the slow action potentials induced by isoprenaline in papillary muscles. It is concluded that (S)-nafenodone exerted fewer cardiodepressant effects than imipramine and desipramine in isolated guinea-pig atrial and ventricular muscle fibres less.

Effects of lofepramine on human sleep: a pilot study

The influence on objective and subjective sleep variables and tolerance of lofepramine (140 mg) given as a single night time dose was compared with placebo in a double-blind cross-over study. Four healthy male volunteers on the same 2 nights of 2 consecutive weeks took either lofepramine or placebo in a randomized order. On 2 successive mornings of the third week all subjects took 140 mg lofepramine after breakfast. The main variables were electrophysiological measures of all night sleep. Supplementary, scores on a sleep questionnaire after each night, and scores on a side-effect questionnaire every morning and evening of the experiment were obtained. Lofepramine reduced paradoxical sleep and increased REM latency. There was a tendency for more intra-sleep restlessness but no relevant changes in sleep continuity variables. In these subjects lofepramine did not change subjective judgement of sleep quality and of feeling refreshed after sleep. No side-effects were reported.

Lofepramine. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy in depressive illness

Lofepramine is a tricyclic antidepressant that is structurally similar to imipramine and is extensively metabolised to desipramine. In the absence of other major pharmacological effects it appears that its antidepressant activity stems from the facilitation of noradrenergic neurotransmission by uptake inhibition, and possibly by the additional facilitation of serotoninergic neurotransmission. The overall therapeutic efficacy of lofepramine is comparable to that of imipramine, amitriptyline, clomipramine, maprotiline and mianserin in patients with depression of varying severity, and coexisting anxiety. Dry mouth is the most commonly reported side effect of usual therapeutic doses of lofepramine, but the incidence of this and other anticholinergic side effects is less among patients treated with lofepramine than with imipramine. Lofepramine has not been associated with adverse effects on cardiac function even in cases of attempted suicide by overdose. Thus, providing its apparent favourable side effect profile is confirmed in practice, lofepramine may be a valuable alternative for treatment of the depressed patient where a tricyclic is indicated.

An investigation of the effects of lofepramine, nomifensine, amitriptyline and placebo on aspects of memory and psychomotor performance related to car driving

Ten healthy, female volunteers took part in a double-blind, placebo-controlled study to investigate the effects of lofepramine 70 mg, lofepramine 140 mg, nomifensine 100 mg, amitriptyline 50 mg and placebo on psychomotor performance related to driving. One subject failed to complete the study for reasons unrelated to the medications. Each subject received each of the treatments in random order at weekly intervals and was then assessed for psychomotor performance, sedation and quality of sleep. Amitriptyline 50 mg served as a positive control producing results consistent with its known sedative properties. In contrast, lofepramine 70 mg and 140 mg and nomifensine 100 mg were generally free from any significant effect on psychomotor performance.

A comparison of the pharmacological properties of the novel tricyclic antidepressant lofepramine with its major metabolite, desipramine: a review

The effects of the novel tricyclic antidepressant lofepramine were compared with that of its principal metabolite desipramine. In double-bind clinical trials, lofepramine has been shown to be as effective as desipramine and other comparator tricyclic antidepressants in the treatment of endogenous and reactive depression, but there are some differences between them. Thus the acute toxicity of lofepramine is approximately one-fifth that of its metabolite; lofepramine is a less potent muscarinic receptor antagonist than desipramine (verified by clinical studies in volunteers and depressed patients); lofepramine is less likely to produce conduction defects than desipramine. Neurochemical studies show that both lofepramine and its metabolite are potent noradrenaline uptake inhibitors in vitro and evidence is presented to suggest that lofepramine may release this amine following chronic administration in vivo; both drugs slightly increase serotonin turnover under these conditions and down-regulate cortical beta-adrenoceptor function. Unlike desipramine and most clinically effective antidepressants, lofepramine was inactive in attenuating the hyperactivity of olfactory bulbectomized rats in the "open field" apparatus, and in reversing acute clonidine induced hypomotility. From such tests it appears unlikely that the active metabolite, desipramine, is formed in the brain in sufficient concentrations after chronic lofepramine administration to make a substantial contribution towards the pharmacological activity of the parent compound.

Effect of changing transit time on colonic microbial metabolism in man

An investigation was made of the effect of changing mean transit time (MTT) by administration of drugs which affect colonic motility on faecal microbial mass in man. Senokot was used to accelerate and codeine and/or loperamide to prolong transit in subjects maintained on a constant high fibre diet. Doses of Senokot or codeine/loperamide were adjusted to halve or double transit time measured during a three week control period on diet alone. Stools were collected throughout and analysed for bacterial mass by a gravimetric procedure. Transit was measured by a continuous marker method. Senokot decreased mean transit time from 63.9 to 25.0 hours (n = 6), with increased stool weight from 148 to 285 g/day. Bacterial mass increased in all subjects from a mean of 16.5 to 20.3 g/day (dry weight) (p less than 0.025). Codeine/loperamide increased mean transit time from 47.1 to 87.6 hours (n = 5), with decreased stool weight from 182 to 119 g/day. Bacterial mass decreased in all but one subject from a mean of 18.9 to 16.1 g/day (NS). There was a significant correlation between transit time and bacterial mass in all three periods (r = 0.77, p less than 0.001). Changes in transit time are shown to alter microbial growth in the human colon and result in altered stool output, on a constant diet. Factors which affect transit may be as important as diet in determining large bowel function and hence susceptibility to disease.

Effects of phenothiazines and dibenzazepines on axonal transport and microtubule assembly in vitro

Various phenothiazines (thioridazine, trifluoperazine and chlorpromazine) and dibenzazepines (lofepramine, amitriptyline and desipramine) were studied for effects on fast axonal transport (AXT) in vitro in frog sciatic nerves. AXT, measured as the accumulation of (3H) leucine-labelled proteins in front of a ligature, was inhibited by more then 50% by all the drugs tested at 0.2 mM concentrations. Thioridazine and lofepramine were the most potent inhibitors. These effects were not due to decreased ganglionic incorporation. Some of the drugs also reduced the levels of high energy phosphates, adenosinetriphosphate (ATP) and creatinephosphate (CrP), but not to an extent which is likely to explain the arrested AXT. The polymerization of purified brain tubulin was inhibited by the phenothiazines but unaffected by the dibenzazepines at concentrations which inhibited AXT. Phenothiazines and dibenzazepines are chemically related and known to have a high affinity for calmodulin. The possibility that these drugs interefere with calmodulin regulated processes of importance for AXT will be discussed.

Actions of lofepramine, a new tricyclic antidepressant, and desipramine on electrophysiological and mechanical parameters of guinea pig atrial and papillary muscles

The effects of lofepramine on the isolated guinea pig atrial trabeculae were compared with those of desipramine. The preparations were taken from the same animal and mounted in the same tissue bath. All parameters were recorded in parallel. Lofepramine 10 microM was shown to exhibit minor changes in the transmembrane action potential duration only. The action potentials of the atrial trabeculae were prolonged, whereas they were shortened in the papillary muscles. Desipramine was about ten times more potent than lofepramine, but produced similar qualitative changes. Desipramine 10 microM and lofepramine 100 microM showed local anaesthetic properties: a decreased overshoot without a decreased resting potential, a decreased and rate-dependent Vmax, and a decrease in propagation velocity. After the addition of either drug in a lower concentration, a transient increase in force development and a concomitant increase in repolarization phase height (atrial trabeculum) or plateau length (papillary muscle) were recorded. The steady state effect on the force development was a decrease accompanied by a shortening of the action potential duration (papillary muscle). It is suggested that the action of lofepramine 100 microM and desipramine 10 microM on phase 0 of the action potential are produced by blockage of the fast sodium channel. The transient increase in developed force and the increase in repolarization phase height (atrial trabeculum) or plateau length (papillary muscle) could be caused by inhibition of the membrane re-uptake system for released noradrenaline. The steady state shortening and flattening of the plateau (papillary muscle) and the decrease in force development could be the cause of a block in the slow channel system.

[Lofepramine: a comparative clinical study with amitriptyline]

Lofepramine, a new tricycle antidepressant, is compared with amitriptyline in a double-blind study. A brief pharmacological description of the drug is made emphasizing its low toxicity and anticholinergic peripheral effects, high plasmatic concentration levels and good tolerance and elimination in comparison with some other known tricycle antidepressants. Sixty depressive outpatients of a Mental Health Service in Lima, 5 male and 55 female, aging 16 to 65, 29 endogenous and 31 neurotic were studied with both drugs in a equimolar dosage. Through the chi square test, no statistical significance was found in maximal therapeutic response, Hamilton Depression Rating Scale scores, type of depression, and side-effects xerostomy which is lesser with lofepramine. A discussion of these results is made and it is concluded that in the present study lofepramine compared with amitriptyline has a similar therapeutic effect. Though not statistically significant, lofepramine seems to be better for neurotic depression and patients sensitive to anticholinergic side-effects.