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Muscarinic m4 receptor activation by some atypical antipsychotic drugs.

To clarify the findings that clozapine is both a muscarinic receptor agonist and antagonist, we examined the effects of neuroleptics on forskolin-stimulated cAMP accumulation in Chinese hamster ovary cells expressing human muscarinic m4 receptors (CHO-hm4) and in rat striatum. With CHO-hm4 cells, clozapine induced a concentration-dependent and atropine-sensitive inhibition on cAMP formation, with EC50 = 60 nM and Emax = 74% of carbachol maximum. Other atypical neuroleptics, fluperlapine, tenilapine and olanzapine, were similar but less potent, while risperidone, rilapine, quetiapine (ICI 204,636), sertindole, and ziprasidone had almost no effect. Typical neuroleptics, haloperidol, chlorpromazine, fluphenazine, thiothixene, thioridazine, and molindone, showed either no effect or an atropine-resistant inhibition of cAMP formation. However, in rat striatal tissues, clozapine, up to 10 microM, did not show a significant inhibition of cAMP formation, probably due to a relatively low abundance of muscarinic m4 receptors and the presence of multiple types of muscarinic and other receptors, with which clozapine interacts. Nevertheless, muscarinic m4 receptor agonism, to some extent, may be a relevant mechanism for the therapeutic efficacy and side effects of clozapine and some atypical neuroleptics.

Animals↗

Effects of neuroleptics on phencyclidine (PCP)-induced locomotor stimulation in mice.

A variety of neuroleptics were compared for their ability to block phencyclidine (PCP)-induced behavioral stimulation in mice. Methiothepin, fluphenazine, trifluoperazine, and chlorpromazine were highly effective in blocking phencyclidine-induced stimulation at doses that did not decrease spontaneous behavioral activity. Clozapine, thioridazine and haloperidol were moderately effective, while sulpiride, molindone, and pimozide were completely ineffective. The effectiveness of the drugs was found to be correlated with their ability to block tryptamine-induced seizures and with several other measures of antidopaminergic and antiserotonergic potency. it is concluded that a combination of antidopaminergic and antiserotonergic activity is important for blocking the stimulating effects of phencyclidine.

Animals↗

A dopamine receptor model and its application in the design of a new class of rigid pyrrolo[2,3-g]isoquinoline antipsychotics.

A hypothetical model of the interaction of antipsychotic drugs with the dopamine receptor is described. This three-dimensional molecular model has been developed on the basis of plausible intermolecular interactions between pharmacophoric groups of diverse types of antipsychotic drugs and postulated amino acid side chain substituents of the receptor protein. Three essential binding sites (one possibly required for antagonism) and one lipophilic auxiliary binding site are identified. The geometry is defined via the three-dimensional structures of drugs exhibiting receptor activity, including (R)-apomorphine, (+)-dexclamol, and molindone (whose crystal structure has been determined). A new conformationally rigid pyrrolo[2,3-g]isoquinoline derivative has been designed to conform to the receptor model. The compound (+/-)-1 (2,6-dimethyl-3-ethyl-4,4a,5,6,7,8,8a,9-octahydro-4a,8a-trans-1H-pyrrolo[2,3-g] isoquinolin-4-one; Ro 22-1319) exhibits potent antipsychotic-like activity. The activity is stereospecific, residing in the (-) enantiomer, predicted and confirmed by X-ray crystal structure analysis of (-)-1.HCl to have the 4aR,8aR absolute configuration.

Animals↗

Antipsychotic drugs which elicit little or no parkinsonism bind more loosely than dopamine to brain D2 receptors, yet occupy high levels of these receptors.

This review addresses two questions. First, why does clozapine apparently occupy low levels of dopamine D2 receptors in patients, in contrast to all other antipsychotic drugs which occupy 70-80% of brain dopamine D2 receptors? Second, what is the receptor basis of action of antipsychotic drugs which elicit low levels of Parkinsonism? Antipsychotic doses of clozapine occupy between 0% and 50% of D2 receptors, as measured in patients by a variety of radioligands. It has recently been found, however, that the percent occupancy of a receptor by a drug depends on the radioligand used to measure that receptor. Based on this new finding, this review concludes that clozapine clinically occupies high levels of D2 receptors in the absence of any radioligand. This occupancy is estimated to be of the order of 70-80% in the dopamine-rich region of the human striatum, and even higher in the limbic D2-containing regions which are low in endogenous synaptic dopamine. This conclusion arises from two different approaches. One approach is to relate the reported clozapine occupancies in the human striatum with the dissociation constants of the various radioligands at the D2 receptor. This relation extrapolates to approximately 70-80% occupancy by clozapine when clozapine competes with endogenous dopamine at the D2 receptor. The second approach is to calculate the D2 occupancy of each antipsychotic drug, using the average spinal fluid concentration and the correct dissociation constant of the antipsychotic, thereby revealing that all antipsychotic drugs, including clozapine, occupy approximately 70-80% of dopamine D2 receptors in the human striatum, and possibly higher in the limbic regions. As determined by the new dissociation constants, antipsychotic drugs which elicit Parkinsonism (trifluperazine, chlorpromazine, raclopride, haloperidol, fluphenazine, risperidone) bind more tightly than dopamine to D2, while those antipsychotic drugs which elicit little or no Parkinsonism (melperone, seroquel, perlapine, clozapine, remoxipride, molindone, sulpiride, olanzapine, sertindole) bind more loosely than dopamine to D2 receptors. Compared to the tightly bound antipsychotic drugs, the more loosely bound antipsychotics generally require higher clinical doses, require fewer days for clinical adjustment, but may dissociate from the D2 receptor more rapidly and could lead to clinical relapse somewhat earlier than that found with the traditional tightly bound antipsychotic drugs.

Antipsychotic Agents↗

Obesity and related metabolic abnormalities during antipsychotic drug administration: mechanisms, management and research perspectives.

Excessive body weight gain (BWG) is a common side effect of some typical and atypical antipsychotic drugs (APs). Convergent evidence suggests a hierarchy in the magnitude of BWG that may be induced by diverse agents, being very high for clozapine and olanzapine; high for quetiapine, zotepin, chlorpromazine, and thioridazine; moderate for risperidone and sertindole; and low for ziprazidone, amisulpiride, haloperidol, fluphenazine, pimozide, and molindone. BWG may be related to increased appetite that is due to drug interaction with the brain monoaminergic and cholinergic systems and to the metabolic/endocrine effects of hyperprolactinemia. Subjects with schizophrenia and bipolar disorders manifested a significantly high prevalence of diabetes, even before the introduction of atypical APs. However, clozapine and olanzapine appear to display a high propensity to induce glucose dysregulation and dyslipidemia. Sudden BWG, insulin resistance, increased appetite, and related endocrine changes also may be involved in the development of glucose intolerance and dyslipidemia in predisposed individuals. Patients should be informed of these side effects in order to prevent excessive BWG, and their blood glucose and lipids should be monitored before treatment and then at regular intervals. Nutritional advice must be given and regular physical exercise recommended. An appropriate selection of APs ought to be based on drug efficacy for specific patients and assessment of relevant risk factors such as propensity to gain weight; family or personal history of diabetes or hyperlipidemia; and elevated fasting serum glucose, lipid, or insulin levels. At present, there is no standardized pharmacological treatment for AP-induced BWG. Some studies have assessed the effects of agents such as amantadine, orlistat, metformin, nizatidine, and topiramate on AP-induced BWG. Further studies will provide tools to identify patients at high risk for obesity and metabolic abnormalities during AP administration. Excessive body weight gain (BWG), glucose intolerance, and dyslipidemia during treatment with antipsychotic drugs (APs) were reported in the late 1950s [14,101]. However, after 1990, interest in these problems increased noticeably, mainly because of the high propensity of some new atypical APs to induce these side effects (Fig.1). The APs are currently used in diverse mental disorders. Hence, excessive BWG and metabolic dysfunction are not exclusive of subjects with schizophrenia. In the case of bipolar disorders, AP-induced BWG may be additive to that induced by mood stabilizers [14,48,101]. The clinical features [2,14,24,133,139,140] and mechanisms [14,34,68,87,93,101,130] of BWG and metabolic dysfunction have been previously reviewed. In this article, we focus on a unified theory to explain these side effects, based on the interaction of APs with brain neurotransmitters involved in appetite regulation. This review comprises the following sections: 1) the clinical features of AP-induced BWG; 2) the effects of APs on carbohydrate and lipid metabolism in humans and experimental animals; 3) mechanisms involved in BWG, glucose, and lipid dysregulation; 4) strategies for prevention and treatment of these side effects; and 5) research perspectives in the field. The following sources were consulted: MEDLINE, Cochrane database system, and PsychINFO. Numerous articles referred to in leading articles also were consulted. The literature on this subject has increased so rapidly that it was impossible to include all the data recently published. For the first two sections, references that illustrate current controversies in the field were selected.

Animals↗

Sodium ion modulates D2 receptor characteristics of dopamine agonist and antagonist binding sites in striatum and retina.

Sodium ion (Na(+)) influences binding of both dopamine agonists and antagonists to D(2) receptors in striatum and retina. Also, Na(+) markedly potentiates the loss of high-affinity agonist binding due to the GTP analogue p[NH]ppG. 2-Amino-6, 7-dihydroxy-1,2,3,4-tetrahydro[5,8-(3)H]naphthalene ([(3)H]ADTN) binds exclusively to an agonist conformation of D(2) receptor in both striatum and retina, distinct from the antagonist conformation labeled by [(3)H]spiroperidol or [(3)H]domperidone in striatum or by [(3)H]spiroperidol in retina. Na(+) is not required for interaction of [(3)H]ADTN or antagonist radioligand sites with the selective D(2) agonist LY-141865, the D(2) antagonist domperidone, or nonselective dopamine agonists or antagonists; however, Na(+) is necessary for high affinity interaction of those radioligand sites with the D(2) antagonists molindone and metoclopramide. With Na(+) present, striatal sites for [(3)H]ADTN, [(3)H]spiroperidol, and [(3)H]domperidone have similar affinities for antagonists but only [(3)H]ADTN sites have high affinity for agonists. Na(+) further decreases the low affinity of dopamine agonists for [(3)H]spiroperidol binding sites. Also, Na(+) enhances [(3)H]spiroperidol and decreases [(3)H]ADTN binding. Na(+) alone causes bound [(3)H]ADTN to dissociate from at least 30% of striatal and 50% of retinal sites, and with Na(+) present [(3)H]ADTN rapidly dissociates from the remaining sites upon addition of p[NH]ppG. It is proposed that D(2) receptors in striatum and retina exist in distinct but interconvertible conformational states, with different properties depending on the presence or absence of Na(+) and of guanine nucleotide.

Animals↗

Sigma opiates and certain antipsychotic drugs mutually inhibit (+)-[3H] SKF 10,047 and [3H]haloperidol binding in guinea pig brain membranes.

The relationship between binding of antipsychotic drugs and sigma psychotomimetic opiates to binding sites for the sigma agonist (+)-[3H]SKF 10,047 (N-allylnormetazocine) and to dopamine D2 sites was investigated. In guinea pig brain membranes, (+)-[3H]SKF 10,047 bound to a single class of sites with a Kd of 4 X 10(-8) M and a Bmax of 333 fmol/mg of protein. This binding was different from mu, kappa, or delta opiate receptor binding. It was inhibited by opiates that produce psychotomimetic activities but not by opiates that lack such activities. Some antipsychotic drugs inhibited (+)-[3H]SKF 10,047 binding with high to moderate affinities in the following order of potency: haloperidol greater than perphenazine greater than fluphenazine greater than acetophenazine greater than trifluoperazine greater than molindone greater than or equal to pimozide greater than or equal to thioridazine greater than or equal to chlorpromazine greater than or equal to triflupromazine. However, there were other antipsychotic drugs such as spiperone and clozapine that showed low affinity for the (+)-[3H]SKF 10,047 binding sites. Affinities of antipsychotic drugs for (+)-[3H]SKF 10,047 binding sites did not correlate with those for [3H]spiperone (dopamine D2) sites. [3H]-Haloperidol binding in whole brain membranes was also inhibited by the sigma opiates pentazocine, cyclazocine, and (+)-SKF 10,047. In the striatum, about half of the saturable [3H]haloperidol binding was to [3H]spiperone (D2) sites and the other half was to sites similar to (+)-[3H]SKF 10,047 binding sites.

Animals↗

Weight gain associated with neuroleptic medication: a review.

In this article we review the empirical literature on weight gain associated with neuroleptic drug use. Weight gain, which appears to be associated with an increase in appetite, is variable but likely to be larger initially and then plateau. Clozapine and low-potency phenothiazines are associated with the largest gains and molindone with weight loss, but the mechanism is not known. Amantadine and fenfluramine may reverse weight gain to some degree. Dietary fat seems to play an important role in obesity, and research is needed to increase the data base and elucidate possible mechanisms. Studies are also needed to evaluate preventive strategies and to determine which drugs are least likely to produce weight gain as well as which drugs could be added to a neuroleptic regimen to control weight.

Antipsychotic Agents↗

Which atypical antipsychotics are identified by screening tests?

Only two tests were specific for antipsychotic potential. All effective antipsychotics blocked pharmacologically induced locomotion and affected firing in the mesolimbic DA neurons. The remaining single- (Table 1) and repeated- (Table 2) dose tests identified the atypical antipsychotics. Clozapine, thioridazine, sulpiride, tiospirone, and molindone were atypical in both types of study. Pimozide, pipamperone, aceperon, methylperon, and clotiapine were atypical in single-dose studies, clopenthixol in repeated-dose studies. Since the biochemical abnormality causing psychoses is unknown, it may be that current methods of screening for new antipsychotics are inadequate and possibly inappropriate. If a neurotransmitter other than DA is the primary cause, then totally new tests may be needed. Present tests, especially those involving behavioral paradigms, may continue to select out compounds that cause EPS side-effects. New methods such as positron emission tomography scanning and other brain-imaging techniques hold the promise of studying specific types and subtypes of receptors in the living human brain. The recent discovery of chromosomal abnormalities in psychotic illness may provide new insights into the biochemical causes of such disorders and lead to completely new compounds that will be both safer and more effective. In the meantime we plan to review the literature on the clinical use of the compounds identified as atypical in this article and to develop research protocols to assess their efficacy in treatment-resistant psychoses and intractable conditions such as tardive dyskinesia.

Animals↗

[3H]Spiperone labels non-cyclase-linked dopamine receptors in the ventral tegmental area of rat brain.

The binding of [3H]spiperone, a neuroleptic/dopamine receptor ligand, to membranes of the ventral tegmental area of the rat was studied in vitro and found to be rapid, saturable, reversible, and of high affinity. Specific binding was displaced by the dopaminergic agonists dopamine, apomorphine, and 2-amino-6,7-dihydroxytetralin, and stereospecifically by the neuroleptic drugs butaclamol and flupenthixol. Bromocryptine and other ergots displaced the binding, as did the D-2 antagonists domperidone, molindone, metoclopramide, and sulpiride. Noradrenergic, histaminergic, and serotonergic components of the binding were not detected in displacement studies with various agonists and antagonists. These data are consistent with the hypothesis that [3H]spiperone labels dopamine receptors in the ventral tegmental area that are not linked to adenylate cyclase and are therefore likely to be of the D-2 type.

Adenylyl Cyclases↗

Neurochemical studies of the mesolimbic dopaminergic pathway: [3H]spiperone labels two bindings sites in homogenates of the nucleus accumbens of rat brain.

The binding of [3H]spiperone to membranes of the nucleus accumbens of the rat brain was studied in vitro and found to be of high affinity, rapid, saturable, reversible and stereospecific. Dissociation and saturation experiments indicated the presence of two specific binding sites with apparent dissociation constants of 70 pM and greater than 1 nM. Specific binding with 25 pM [3H]spiperone represented greater than 90% of total binding and was displaced by dopaminergic agonists, neuroleptic drugs and ergot derivatives. The rank order of potency for the ergot derivatives was bromocryptine greater than pergolide greater than lergotrile, and that for D-2 antagonists was domperidone greater than sulpiride greater than molindone greater than metoclopramide. Noradrenergic, histaminergic and serotonergic components of the binding were not detected. [3H]Spiperone binds to high-affinity sites in homogenates of nucleus accumbens, which are likely to be D-2 receptors.

Animals↗

The clinical impact of reported variance in potency of antipsychotic agents.

There is significant disagreement on the clinical equivalence (or potency) of antipsychotic agents, with up to 500% variance reported in texts. To address the extent and consequences of these discrepancies, we took a random sample of 18 common psychiatry, psychopharmacology and pharmacology texts for antipsychotic equivalence tables. We found a marked variation in stated equivalences for the majority of antipsychotics. Most affected were the high potency (haloperidol, fluphenazine) and newer (molindone) drugs, which had a 500% variance. This variation inadvertently contributes to the misuse of these agents. For instance, high-potency antipsychotics are prescribed in far larger doses than necessary, leading to decreased efficacy and increased side effects. Steps to simplify and rationalize the use of these agents are recommended.

Antipsychotic Agents↗

In vitro human plasma leucine(5)-enkephalin degradation is inhibited by a select number of drugs with the phenothiazine molecule in their chemical structure.

A number of drugs with the phenothiazine molecule in their chemical structure inhibit in a dose-dependent manner human plasmatic aminopeptidase leucine(5)-enkephalin (LEU) metabolism. Half-life peptide degradation was significantly increased by thioridazine > fluphenazine > As-1397 [10-(alpha-diethylaminopropionyl)phenothiazine] >/= promethazine >/= chlorpromazine (final drug conc. 10(-4) M); t1/2 (+/- SD) 21.2 +/- 1.1, 19.6 +/- 1.0, 17.2 +/- 0.9, 17.1 +/- 1.0, and 17.1 +/- 1.1 min, respectively. Control and bacitracin (known aminopeptidase inhibitor) values were 11.8 +/- 1.0 and 31.3 +/- 1.7 min, respectively. These drugs significantly decreased (listed in the same order) LEU degradation initial velocity; Iv (+/- SD) 0.77 +/- 0.2, 0.82 +/- 0.2, 0.92 +/- 0.3, 0.93 +/- 0.2, 0.94 +/- 0.3 pg LEU/min, respectively. Control and bacitracin 1.10 +/- 0.3 and 0.20 +/- 0.1 pg LEU/min, respectively. Values represent results from 5 samples, each obtained by pooling 6 individual plasmas (4 male and 2 female; n = 30 healthy, drug-free volunteers). However, neither the phenothiazines ethopropazine, methotrimeprazine, prochlorperazine and trifluoperazine nor the various commonly used heterocyclic antipsychotics tested, e.g., molindone, loxapine, clozapine, haloperidol, sulpiride and thiothixene inhibited plasma LEU degradation kinetics. Our results failed to show correlations between chemical structure, antipsychotic properties and ability to inhibit plasmatic aminopeptidase LEU degradation. Whereas, presence of the phenothiazine molecule appears to be necessary for enzyme inhibition, only five out of nine substituted phenothiazines tested exhibited this effect. Furthermore, there was a lack of correlation between phenothiazines antipsychotic properties and their capacity to inhibit aminopeptidase activity, a property shown by promethazine (antihistaminic) and As-1397 (selective butyrylcholinesterase inhibitor) but lacking in prochlorperazine and trifluoperazine. Our results provide information which could lead to the rational design of agents capable to modulate the bioavailability of enkephalin and other endogenous aminopeptidase-degraded peptides believed to be involved in the etiology and/or pathophysiology associated with various disease conditions. Whether their development could find useful pharmacological applications remains to be explored.

Adult↗

Clinical state and serum neuroleptic levels measured by radioreceptor assay in schizophrenia.

The authors measured serum neuroleptic levels by radioreceptor assay in 30 schizophrenic patients receiving haloperidol, fluphenazine, chlorpromazine, molindone, thiothixene, or trifluoperazine. Neuroleptic levels were significantly correlated with clinical state, monitored by an abbreviated version of the Present State Examination (the mini-PSE). Poor therapeutic responses were associated with serum levels under 50 ng/ml chlorpromazine equivalents. There was no correlation between neuroleptic dosage and mini-PSE score or between neuroleptic dose and serum neuroleptic levels.

Adolescent↗

Successful use of clozapine in a patient with a history of neuroleptic malignant syndrome.

Reinstitution of antipsychotic medication is problematic in patients with a history of neuroleptic malignant syndrome (NMS). In this case, a patient with a history of probable neuroleptic malignant syndrome caused by administration, as single agents, of haloperidol, molindone, and lithium was later treated successfully with the novel antipsychotic clozapine. The propensity of various antipsychotic agents to cause NMS is discussed.

Activities of Daily Living↗

Systematic review of antipsychotics for the treatment of hospital-associated delirium in medically or surgically ill patients.

OBJECTIVE: To determine which antipsychotic is associated with the greatest efficacy and safety when used for the pharmacotherapeutic management of delirium in medically or surgically ill patients. DATA SOURCES: MEDLINE, Current Contents, Cumulative Index of Nursing and Allied Health Literature, PsycINFO, Biological Abstracts, Cochrane Central Register of Controlled Trials, and EMBASE databases (all to July 2006) were searched for trials evaluating the pharmacologic treatment of delirium in medically or surgically ill patients. The key terms used included delirium, agitation, or acute confusion, and antipsychotics, phenothiazine, butyrophenone, perphenazine, fluphenazine, clozapine, trifluorophenazine, loxapine, thioridazine, pimozide, molindone, haloperidol, methotrimeprazine, chlorpromazine, prochlorperazine, droperidol, risperidone, quetiapine, ziprasidone, amisulpride, or olanzapine. STUDY SELECTION AND DATA EXTRACTION: Prospective, randomized, controlled trials comparing the clinical effects of antipsychotic therapy with placebo or comparing 2 antipsychotic treatments in an acute care setting were selected. Studies involving dementia-associated delirium, Alzheimer's disease-associated delirium, emergency department-associated acute agitation, acute brain trauma-associated agitation, or agitation secondary to underlying psychiatric afflictions such as depression or schizophrenia were excluded. All studies were evaluated independently by the 3 authors using a validated evaluation tool. Outcomes related to both efficacy and safety were collected. Four prospective trials were included in this systematic review. DATA SYNTHESIS: Antipsychotic agents, either atypical or typical, were effective compared with baseline for the treatment of delirium in medically or surgically ill patients without underlying cognitive disorders. Oral haloperidol was associated with more frequent extrapyramidal side effects, but overall, all agents were well tolerated. Interpretation of the published evidence is limited by the small sample sizes, varied patient populations, and comparative agents of the studies reviewed. CONCLUSIONS: The comparative studies evaluated here suggest that antipsychotic drugs are efficacious, when compared with baseline, and safe for the treatment of delirium. Haloperidol remains the most studied agent. Recommendation of one antipsychotic over another as a first-line pharmacologic intervention in the treatment of hospital-associated delirium is limited by the quality and quantity of data available. Better designed and larger studies evaluating the addition of antipsychotic agents to nonpharmacologic treatments are needed to measure the true effect of pharmacologic treatment.

Antipsychotic Agents↗

Antipsychotic medication and seizures: a review.

Both first-generation and second-generation antipsychotic medications can lower the seizure threshold, increasing the chances of seizure induction. This article reviews the published literature concerning the seizure-lowering effects of first- and second-generation antipsychotic medication. Unfortunately, rigorously controlled studies are relatively infrequent, and case reports form a large part of the available literature, limiting the confidence with which firm conclusions can be drawn. Of the first-generation antipsychotic medications, chlorpromazine appears to be associated with the greatest risk of seizure provocation, although other first-generation antipsychotics also lower seizure threshold. Conversely, molindone, haloperidol, fluphenazine, pimozide and trifluoperazine are associated with a lower risk of seizure induction. Clozapine is the second-generation antipsychotic most frequently associated with seizures, with risperidone appearing to confer a relatively low risk. Other factors such as history of seizure activity, concurrent use of other drugs that lower seizure threshold, rapid dose titration, slow drug metabolism, metabolic factors and drug-drug interactions appear to increase the chances of an antipsychotic medication inducing seizure activity.

Antipsychotic Agents↗

Bodyweight change as an adverse effect of drug treatment. Mechanisms and management.

A number of drugs are capable of changing bodyweight as an adverse effect of their therapeutic action. Bodyweight gain is more of a problem than bodyweight loss. As bodyweight gain during drug treatment for any kind of disease may be the reflection of improvement of the disease itself, we will try to separate these effects from those due to drug-induced alterations of the mechanisms regulating bodyweight. Bodyweight gain may jeopardise patient compliance to the prescribed regimen and it may pose health risks. The body mass index (BMI) is determined by dividing bodyweight in kilograms by height in metres squared. A BMI of > or = 27 kg/m2 warrants therapeutic action; nutritional counselling and programmed physical exercise can be used as a basis. In general, if basic therapeutic measures are unsuccessful at controlling bodyweight gain then a change of drug might help. Finally, an anoretic drug may serve to support dietary measures. However, safety and efficacy has been demonstrated for only a few anorectic drugs when used as an adjunct to caloric restriction in the treatment of drug-induced obesity. Bodyweight is determined by complex mechanisms regulating energy balance. A number of neurotransmitter systems acting in several hypothalamic nuclei are pivotal to the regulation of body fat stores. Most drugs that are capable of changing bodyweight interfere with these neurotransmitter systems. The increment is dependent on the type and dose of the drug concerned. Some antidepressant drugs induce bodyweight gain, which may amount to 20 kg over several months of treatment. Monoamine oxidase inhibitors appear to cause less bodyweight change than tricyclic antidepressants. Selective serotonin (5-hydroxytryptamine; 5-HT) reuptake inhibitors cause bodyweight loss instead of bodyweight gain. Lithium may cause large increases in bodyweight. Generally speaking, the bodyweight change induced by antipsychotics is more often of clinical significance than the bodyweight change associated with the use of antidepressants. Again, the changes of bodyweight are dependent upon the type and dose of the antipsychotic drug involved. Although almost all antipsychotics induce bodyweight gain, molindone and loxapine appear to induce bodyweight loss. Anticonvulsants, especially valproic acid (sodium valproate) and carbamazepine, induce bodyweight gain in a considerable percentage of patients. Treatment with corticosteroids is associated with dose-dependent bodyweight gain in many patients. Corticosteroid-induced obesity aggravates other corticosteroid-associated health risks. Insulin therapy in diabetic patients usually increases bodyweight. Finally, sulphonurea derivatives, antineoplastic agents used for the treatment of breast cancer and several drugs used in migraine prophylaxis may cause bodyweight gain as well.

Antineoplastic Agents↗