Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “AMPHETAMINE”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 343 records · Page 19Linked to original sources
PubMed1988

Amphetamine-induced increase in motor activity is correlated with higher firing rates of non-dopamine neurons in substantia nigra and ventral tegmental area.

The responses of non-dopamine neurons in substantia nigra and ventral tegmental area to systemic amphetamine were investigated in the behaving rat chronically implanted with multiple fine-wire electrodes. The neurons were identified with electrophysiological criteria requiring that the signals be of biphasic shape, short duration (less than 2.0 ms), and show high and regular rates of discharge (greater than 20 spikes/s). In recording sessions lasting 240 min, single and multiple unit activity was recorded from seven electrodes, and motor activity was measured automatically with the open-ended wire technique. The movement counts provided an index of gross motor activity, not of the specific movements occurring during DA behaviors. D-Amphetamine, 5.0 mg/kg, given by the intraperitoneal route at 90 min into the session, induced an increase in motor activity and in the firing rate of some non-dopamine neurons. The behavioral and neural responses were correlated for magnitude, latencies and duration. But not all non-dopamine neurons in ventral tegmental area, and substantia nigra showed responses to amphetamine. When unit responses were obtained, they were obtained in subjects which showed large motor responses. In substantia nigra, responsive and non-responsive units were interdigitated and found mainly in the pars reticulata subdivision. In the ventral tegmental area, responsive and non-responsive neurons were interdigitated throughout this structure. The effects of amphetamine were dose-responsive, doses of 1.0, 2.0 and 3.0 mg/kg inducing smaller behavioral and unit responses than 5.0 mg/kg. D-Amphetamine, 5.0 mg/kg, was more effective than L-amphetamine, given at the same dose, in inducing these changes. In rats pretreated with systemic haloperidol, 1.5 mg/kg, the behavioral and neural responses to D-amphetamine, 5.0 mg/kg, were greatly attenuated. In rats pretreated with a subanesthetic dose of urethan, 600 mg/kg, to prevent changes in gross motor activity, the response to D-amphetamine in ventral tegmental area was attenuated, but it was of normal magnitude in substantia nigra. In rats with bilateral electrolytic lesions of nucleus accumbens, D-amphetamine induced a smaller motor response than in controls, but the neural responses in ventral tegmental area and substantia nigra were the same as in controls. These findings support the notion that non-dopamine neurons in ventral tegmental area and substantia nigra, pars reticulata, play a role in the motor function of the A9 and A10 dopamine neurons, and in the behavioral effects of amphetamine.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1995

Role of vesicular dopamine in the in vivo stimulation of striatal dopamine transmission by amphetamine: evidence from microdialysis and Fos immunohistochemistry.

The role of vesicular and newly synthesized dopamine in the action of amphetamine was investigated by studying the effect of reserpine and alpha-methyl-p-tyrosine pretreatment on amphetamine-induced changes in extracellular dopamine and acetylcholine, estimated by brain microdialysis, and on c-fos expression, estimated by quantitative immunohistochemistry of the Fos antigene, in the dorsal caudate-putamen of rats. Blockade of dopamine synthesis by alpha-methyl-p-tyrosine pretreatment (1 or 2 h) only partially prevented the increase in extracellular dopamine concentrations elicited by 0.5 and 2 mg/kg s.c. of amphetamine. Inactivation of vesicular amine uptake by reserpine pretreatment (3 h) reduced the increase in extracellular dopamine by 2 mg/kg but not by 0.5 mg/kg of amphetamine. Combined pretreatment with reserpine (3 h) and alpha-methyl-p-tyrosine (1 h) drastically reduced the increase in extracellular dopamine by both doses of amphetamine (0.5 and 2 mg/kg s.c.). alpha-Methyl-p-tyrosine pretreatment reduced c-fos expression stimulated by amphetamine (2 mg/kg) in the dorsomedial and dorsolateral caudate-putamen while reserpine pretreatment reduced it only in the dorsolateral caudate-putamen. Amphetamine (2 mg/kg s.c.) stimulated acetylcholine release but this effect was not modified by reserpine or alpha-methyl-p-tyrosine pretreatment. The results indicate that blockade of dopamine synthesis, by itself, is insufficient to prevent the stimulation of dopamine transmission by amphetamine and, conversely, that inactivation of vesicular dopamine significantly reduces amphetamine effects at pre- and postsynaptic levels. Therefore, vesicular dopamine appears to contribute to the stimulation of dopamine transmission elicited by amphetamine in the dorsal caudate-putamen.

Acetylcholine↗
PubMed1988

The influence of brain catecholamines on 'drug taking behaviour' relative to oral self-administration of d-amphetamine by rats.

Oral administration of 5 mg/kg of d-amphetamine to adult Wistar rats caused brain NE to decrease to approx. 80% of the control level during 4-24 h after acute treatment and slowly further to 65% after 24 days of self-administration via drinking water. The norepinephrine (NE)-reducing effect was first recognized at 1 mg/kg and appeared to peak at 5 mg/kg of d-amphetamine. Brain dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) were only shortly affected. Neither iprindole nor desipramine altered the effect of amphetamine on brain NE. DA was decreased by both inhibitors depending on the duration of pre-treatment. Iproniazid and alpha-methyl-p-tyrosine antagonized and potentiated respectively the amphetamine effect on NE- and DA-concentration after 4 days of simultaneous treatment. In the free choice experiment (water vs. 0.005% d-amphetamine solution) rats developed an aversion to amphetamine. The number of rats taking the drug and the consumption by rats still drinking it declined gradually from 100% and approx. 3 mg/kg/day to 50% and approx. 1.5 mg/kg/day, respectively, during 18 days. The time course of the developing aversive reaction to oral amphetamine ran approximately parallel to that of NE-depletion. Iprindole and desipramine intensified, iproniazid and propranolol weakened, while alpha-methyl-p-tyrosine and haloperidol hardly influenced the aversive effect of amphetamine. It is concluded that the development of aversive behaviour in response to oral d-amphetamine is mediated not only through the depleting effect of amphetamine on NE stores but also by its direct stimulation at beta-adrenergic receptors in the CNS.

Administration, Oral↗
PubMed1998

A comparison of the effects of risperidone, raclopride, and ritanserin on intravenous self-administration of d-amphetamine.

These experiments were conducted to examine the effects of simultaneous blockade of dopamine D2 and 5-hydroxytryptamine2 (5-HT) receptor function on responding for intravenous infusions of d-amphetamine. Rats were trained to self-administer d-amphetamine intravenously according to a progressive ratio schedule of reinforcement, in which response requirements increased for successive infusions until responding extinguished. In the first experiment it was shown that increases in the unit infusion dose of d-amphetamine resulted in an increase in the number of amphetamine infusions earned. Thus, the strength of responding for d-amphetamine was linked to the dose of drug received. The mixed D2 and 5-HT2 receptor antagonist risperidone (0.1, 0.2, and 0.4 mg/kg) reduced responding for d-amphetamine (60 microg/kg infusion). The selective D2 antagonist raclopride (0.1, 0.2, and 0.4 mg/kg) also reduced responding for d-amphetamine. In contrast, the selective 5-HT2 antagonist ritanserin (0.63, 1.25, and 2.5 mg/kg) failed to alter amphetamine self-administration. Combined injections of raclopride (0.05 or 0.1 mg/kg) and ritanserin (2.5 mg/kg) were no more effective than injections of raclopride alone in reducing responding for d-amphetamine. Overall, these results suggest that 5-HT2 receptor blockade plays a negligible role in the rewarding effects of d-amphetamine measured by intravenous self-administration, and does not contribute to the suppressant effects of risperidone on this behavior.

Animals↗
PubMed1999

Sensitization of stereotyped behavior to amphetamine is context and response dependent.

The present study was designed to determine whether the environmental context in which amphetamine is administered plays a role in the development of sensitization to the stereotyped behavioral effects of amphetamine in mice. In male CF-1 mice, the dose-response curve for stereotyped behavior elicited by amphetamine was shifted 1.9-fold to the left 48 h after pretreatment with 14 mg/kg amphetamine. Behavioral sensitization only developed in mice that were pretreated in the same or a similar environment as that of the test environment. In addition, when mice were placed in an environment that attenuated the acute expression of stereotyped behavior elicited by the pretreatment dose of amphetamine, sensitization never developed. A further experiment showed that 96% of the mice that expressed stereotypy after the ED50 pretreatment dose of 10 mg/kg amphetamine showed a stereotyped behavioral response to the lesser dose of 7 mg/kg 48 h later, indicating sensitization. In contrast, mice that did not express stereotypy after the ED50 dose of amphetamine failed to show a significant stereotyped behavioral response to amphetamine challenge compared to vehicle-pretreated controls. Therefore, the results indicate that preexposure to a single high dose of amphetamine produces context- and response-dependent sensitization to amphetamine-induced stereotyped behavior.

Animals↗
PubMed1979

The effect of pargyline and desmethylimipramine on monoamine concentrations and amphetamine-induced glycogenolysis in the mouse brain.

1. Pargyline (100 mg/kg) increased the concentration of cerebral noradrenaline dopamine and 5-hydroxytryptamine in the mouse. Amphetamine (5 mg/kg) reduced the concentration of noradrenaline and increased the concentrations of 5-hydroxytryptamine and dopamine. 2. When amphetamine was administered 4 h after an injection of pargyline, the effect of the sympathomimetic drug on the concentrations of noradrenaline and 5-hydroxytryptamine was not altered. The effect on the dopamine content was reversed, amphetamine causing a decrease instead of an increase. 3. Pargyline increased the concentration of cerebral glycogen, whereas amphetamine caused a decrease. 4. The administration of amphetamine 4 h after pargyline resulted in a decrease in brain glycogen similar to that seen after amphetamine alone. 5. These results suggest that the potentiation of the effect of amphetamine on animal behaviour by pretreatment with an inhibitor of monoamine oxidase is not mediated through a central action on noradrenaline release. 6. Amphetamine-induced glycogenolysis was antagonized by 71% by desmethylimipramine (10 mg/kg). 7. The change in glycogen concentration as a function of time after an injection of amphetamine was not modified when 2 consecutive doses of amphetamine were given with an interval between doses of 30 minutes.

Animals↗
PubMed2005

cAMP and extracellular signal-regulated kinase signaling in response to d-amphetamine and methylphenidate in the prefrontal cortex in vivo: role of beta 1-adrenoceptors.

d-Amphetamine and methylphenidate are widely used in the treatment of attention-deficit/hyperactivity disorder. Both drugs increase extracellular norepinephrine and dopamine in the prefrontal cortex, where they are believed to exert their therapeutic effects. However, the molecular mechanisms underlying their action are poorly understood. To investigate the intracellular signaling pathways activated by d-amphetamine and methylphenidate in the prefrontal cortex in vivo in mice, we measured the cAMP-dependent Ser845 phosphorylation of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor GluR1 subunit and the active form of extracellular signal-regulated kinase (ERK). Administration of d-amphetamine (5-10 mg/kg) or methylphenidate (10-20 mg/kg) increased phosphorylation of GluR1. Basal and d-amphetamine-induced GluR1 phosphorylation was reduced by propranolol, a general beta-adrenoceptor antagonist, and betaxolol, a beta1-antagonist, but not by (+/-)-1-[2,3-(dihydro-7-methyl-1H-inden-4-yl)oxy]-3-[(1-methylethyl)amino]-2-butanol (ICI-118,515), a beta2-antagonist. The effect of methylphenidate was also blocked by propranolol and betaxolol. The d-amphetamine effect was slightly potentiated by prazosin, an alpha1-adrenoceptor antagonist, and mimicked by yohimbine, an alpha2 antagonist. Blockade of dopamine or N-methyl-d-aspartate (NMDA) receptors or serotonin depletion had no effect on d-amphetamine-induced GluR1 phosphorylation. d-amphetamine but not methylphenidate increased ERK phosphorylation. This effect required multiple signaling pathways because it was blocked by beta1- and alpha1-adrenoceptor antagonists, by dizocilpine maleate (MK801), an NMDA antagonist, and by serotonin depletion. In contrast, blockade of dopamine receptors had no effect on d-amphetamine-induced ERK phosphorylation. Propranolol and betaxolol increased the hyperlocomotion produced by d-amphetamine and methylphenidate. Thus, both d-amphetamine and methylphenidate potently activate the cAMP pathway in the prefrontal cortex through beta1-adrenergic receptors. This activation could have behavioral consequences and contribute to the treatment of attention-deficit/hyperactivity disorder.

Animals↗
PubMed2002

Spatial and temporal profile of haloperidol-induced immediate-early gene expression and phosphoCREB binding in the dorsal and ventral striatum of amphetamine-sensitized rats.

To determine if D(2) dopamine receptor-mediated nuclear signaling is altered during the development of amphetamine sensitization, we examined the expression of immediate-early gene (IEG) products, Fos, Jun, and Fos-related antigen (FRA), in both controls and amphetamine-sensitized rats after a challenge with the D(2) antagonist haloperidol. When chronic saline- or amphetamine (5 mg/kg, i.p. for 14 days)-treated rats were challenged with 2 mg/kg haloperidol at withdrawal day 3 (w3), more 35-kDa FRA was induced in the ventral striatum of the control group than in the amphetamine-treated rats. In contrast, more Jun and 35-kDa FRA were expressed in the ventral striatum of the amphetamine-treated group than in the controls when haloperidol was given at w10. Topographical analyses indicate that the decrease in FRA immunoreactive neuronal density in amphetamine-treated rats at w3 were located in the dorsolateral caudate/putamen and the nucleus accumbens shell and core subregions. Conversely, the increase in Jun-immunoreactive neurons in amphetamine-treated rats at w10 was observed in the dorsolateral caudate/putamen; in the case of the FRAs, the increase was observed in the nucleus accumbens shell. In addition, the time-dependent profile of IEG expression paralleled the activation of an upstream regulator, cAMP-response element binding protein, in the ventral striatum after haloperidol treatment. These neurochemical changes may be associated with behavioral plasticity, since amphetamine-treated rats displayed a lower amount of locomotor activity when exposed to a novel environment at w3, but had recovered at w10. Overall, the current study reveals that there is a distinct temporal and spatial profile of haloperidol-induced IEG expression and/or CREB phosphorylation in amphetamine-treated rats, suggesting that there is a critical transition between the early and late withdrawal periods.

Amphetamine↗
PubMed2006

Differences in behavioural effects of amphetamine and dopamine-related gene expression in wild-type and homozygous CCK2 receptor deficient mice.

Neuropeptide cholecystokinin (CCK) interacts with dopamine in the regulation of motor activity and motivations. Therefore, in CCK(2) receptor deficient mice the behavioural effects of repeated amphetamine administration and changes in dopamine-related gene expression were studied. Four-day amphetamine (1 mg/kg) treatment induced a significantly stronger motor sensitization in homozygous mice compared to their wild-type littermates. However, in the conditioned place preference test the action of amphetamine was more pronounced in wild-type animals. As opposed to wild-type mice, amphetamine (1-3 mg/kg) did not cause a significant conditioned place preference in homozygous mice. The expression of Tyhy gene was elevated in the mesolimbic structures and Drd2 gene was down-regulated in the mesencephalon of saline-treated homozygous mice in comparison with respective wild-type group. Four-day treatment with amphetamine induced a significant increase in the expression of Tyhy in the mesencephalon, striatum and mesolimbic structures of wild-type mice, whereas in homozygous mice a similar change was evident only in the mesencephalon. Also, the expression of Drd1 gene in the striatum and Drd2 gene in the mesolimbic structures of wild-type mice were up-regulated under the influence of amphetamine. In conclusion, the present study established differences in the behavioural effects of amphetamine in wild-type and homozygous mice. The increased tone of dopaminergic projections from the mesencephalon to mesolimbic structures is probably related to increased amphetamine-induced motor sensitization in homozygous mice. The lack of development of up-regulation of Drd1 and Drd2 genes after repeated treatment with amphetamine probably explains the reduced place conditioning in CCK(2) receptor deficient mice.

Amphetamine↗
PubMed2003

Withdrawal from chronic amphetamine induces depressive-like behavioral effects in rodents.

BACKGROUND: Amphetamine withdrawal and major depression share many behavioral commonalities in humans. Therefore, the examination of the behavioral effects of amphetamine withdrawal in rodents may provide insights into the neurobiological mechanisms underlying both disorders and aid in the development of animal models of depression that are sensitive to antidepressant agents. METHODS: We examined the behavioral effects of withdrawal from chronic continuous infusion of amphetamine (via minipump) in three behavioral paradigms: the intracranial self-stimulation (ICSS) procedure in rats, the modified forced swim test in rats, and the tail suspension test in mice. RESULTS: Amphetamine withdrawal resulted in a prolonged (5 day) deficit in brain reward function as assessed by elevations in ICSS thresholds. Using a similar regimen of amphetamine administration, we examined the behavioral effects of withdrawal in a modified rat forced swim test. Animals that were treated with the highest dose of amphetamine (10 mg/kg/day) exhibited increased climbing behavior and decreased immobility 24 hours after withdrawal; by the 48-hour testing time point, this effect had dissipated. In contrast, animals that had been pretreated with 5 mg/kg/day amphetamine exhibited a pronounced increase in immobility indicative of an increase in "depressive-like" behavior, coupled with decreases in swimming and climbing. In the mouse tail suspension test, both regimens of amphetamine pretreatment induced increases in immobility scores, also indicative of "depressive-like" behavior, 24 hours following withdrawal. CONCLUSIONS: Withdrawal from chronic amphetamine administration results in behavioral changes that may be analogous to some aspects of depression in humans, such as reward deficits (i.e., elevations in brain reward thresholds) and behaviors opposite to those seen after treatment with antidepressant drugs, such as decreased immobility in the forced swim test and the tail suspension test.

Amphetamine↗
PubMed2000

Changes in astrocytic basic fibroblast growth factor expression during and after prolonged exposure to escalating doses of amphetamine.

We have shown that brief exposure to amphetamine leads to sustained glutamate-dependent increases in expression of the neurotrophic, neuroprotective factor, basic fibroblast growth factor, in astrocytes in dopaminergic cell body regions and that blockade of basic fibroblast growth factor in this region prevents the development of behavioral sensitization to amphetamine. Here we examine the effects of prolonged exposure to an escalating-dose regimen of amphetamine known to induce long-lasting sensitization to amphetamine and leading to increases in neuronal dendritic length and spine density in nucleus accumbens and prefrontal cortex and to decreases in spine density in occipital cortex. Astrocytic basic fibroblast growth factor immunoreactivity was increased in both dopaminergic cell body and terminal regions one week after termination of a two-week amphetamine treatment (1-4mg/kg). These effects were not evident one week after a five-week treatment (1-9mg/kg) and, in fact, one month later basic fibroblast growth factor levels in cell body regions were decreased. In the occipital cortex, basic fibroblast growth factor immunoreactivity was decreased one week after the two-week amphetamine treatment, but was not different from that seen in saline-treated animals after the five-week treatment. Increased astrocytic basic fibroblast growth factor expression appears to be an early, but relatively prolonged, response to amphetamine exposure and seems to parallel structural changes induced by repeated drug exposure.These findings suggest that basic fibroblast growth factor may participate in the development of structural changes brought about by amphetamine. The fact that the basic fibroblast growth factor response is not maintained after prolonged intense exposure to amphetamine suggests that the factors that initially induce basic fibroblast growth factor expression are self-regulating.

Amphetamine↗
PubMed2002

Consequences of amygdala kindling and repeated withdrawal from ethanol on amphetamine-induced behaviours.

It has been shown previously that chronic ethanol treatment in mice leads to accelerated behavioural sensitization to psychomotor stimulants [Manley & Little (1997) J. Pharmacol. Exp. Ther., 281, 1330-1339], whilst repeated experience of ethanol withdrawal sensitizes pathways underlying seizure activity (Becker & Hale (1993) Alcohol Clin. Exp. Res., 17, 94-98]. The aim of the current experiment was to investigate the consequences of repeated withdrawal from ethanol on amphetamine-induced behaviours in the rat and compare this with animals with electrical kindling of the amygdala, a procedure that has been shown to enhance alcohol withdrawal seizures [Pinel et al. (1975) Can. J. Neurol. Sci., 2, 467-475]. For the kindling experiments, electrodes were surgically implanted in the left basolateral amygdala and were stimulated daily at the afterdischarge threshold until a criterion of three consecutive stage 5 seizures was reached. Fully kindled rats showed a marginally significant reduction in sensitivity to the locomotor stimulant effects of acute amphetamine compared with sham and partially kindled rats which had experienced subthreshold stimulation of the amygdala. Sham and partially kindled rats sensitized readily to the locomotor activating effects of amphetamine (0.125 mg/kg) following repeated treatments, but the fully kindled rats did not. Fully kindled rats also failed to show place preference conditioning to amphetamine (0.5 mg/kg). Rats, withdrawn three times from chronic ethanol (liquid-diet), kindled more quickly to PTZ (30 mg/kg, i.p.) than rats with the same overall exposure to ethanol (24 days) followed by a single withdrawal or control animals. However, there was no difference in the locomotor stimulating effects of acute amphetamine (0.25-1 mg/kg, i.p.), the rate of sensitization to amphetamine (0.125 mg/kg, i.p.) or amphetamine induced conditioned place preference (1 mg/kg, i.p.). These observations suggest that, in rats, repeated withdrawal from a relatively mild chronic ethanol treatment modulates neuronal systems that may also be involved in PTZ-induced kindling but not those involved in either the acute stimulant effects of amphetamine or behavioural sensitization or appetitive conditioning following repeated amphetamine administration. Behavioural changes following amygdala kindling differed from those following repeated ethanol withdrawal, suggesting that withdrawal kindling from a mild ethanol treatment differs in its effects from amygdala kindling.

Action Potentials↗
PubMed1999

Metabolic production of amphetamine following multidose administration of clobenzorex.

The interpretation of urine drug-testing results can have important forensic and legal implications. In particular, drugs that are metabolized to amphetamine or methamphetamine or both pose significant concerns. In this study, clobenzorex, an anorectic drug that is metabolized to d-amphetamine, was administered to five subjects. Each subject took 30 mg daily for seven days, and individual urine samples were collected ad lib for 14 days beginning on the first day the drug was administered. Urine pH, specific gravity, and creatinine values were determined for each sample. Gas chromatography-mass spectrometry (GC-MS) was used to determine the excretion profile of amphetamine and clobenzorex using a standard procedure for amphetamines with additional monitoring of ions at m/z 118, 125, and 364 for the detection of clobenzorex. Peak concentrations of amphetamine were found at 82 to 168 h after the first dose and ranged from approximately 2900 to 4700 ng/mL amphetamine. The use of a regioisomer (3-Cl-benzylamphetamine) as internal standard allowed for accurate quantitation of the parent drug. Peak concentrations of clobenzorex were found at 50 to 120 h after the first dose and ranged from approximately 8 to 47 ng/mL clobenzorex. However, in many samples, clobenzorex was not detected at all. This analysis revealed that the metabolite, (amphetamine) is present in much higher concentrations than the parent compound, clobenzorex. Yet even at peak amphetamine concentrations, the parent was not always detected (limit of detection 1 ng/mL). Thus, in the interpretation of amphetamine-positive drug-testing results, the absence of clobenzorex in the urine sample does not exclude the possibility of its use.

Amphetamine↗
PubMed2000

Differentiation of clobenzorex use from amphetamine abuse using the metabolite 4-hydroxyclobenzorex.

Clobenzorex (Asenlix) is an anorectic drug metabolized by the body to amphetamine, thus causing difficulty in the interpretation of amphetamine-positive drug tests. Previous studies have shown the parent drug and several metabolites are excreted in urine. Clobenzorex itself has been detected for as long as 29 h postdose using a detection limit of 1 ng/mL. Despite this fact, several amphetamine-positive samples (> or = 500 ng/mL) contained no detectable clobenzorex. Thus, the absence of clobenzorex in the urine does not exclude the possibility of its use. To more definitively assess the possibility of clobenzorex use, evaluation of another metabolite was considered. One study reported the presence of unidentified hydroxy metabolites of clobenzorex for as long as amphetamine was detected in some subjects. To assess the viability of using a hydroxy metabolite to confirm the use of clobenzorex in samples containing amphetamine, 4-hydroxyclobenzorex was synthesized for this study. This metabolite proved to be easily detected and was typically found at levels higher than amphetamine in amphetamine-positive urines, long after clobenzorex itself was no longer detected. Samples obtained from a controlled single-dose study involving the administration of clobenzorex (30 mg) were analyzed for the presence of the 4-hydroxy metabolite. The analytical procedure used acid hydrolysis followed by liquid-liquid extraction and analysis with gas chromatography-mass spectrometry by monitoring ions at m/z 125, 330, and 364. 4-Hydroxyclobenzorex and its 3-Cl regioisomer were used in the identification and quantitation of the metabolite. Peak concentrations of 4-hydroxyclobenzorex were found at approximately 1:30-5:00 h postdose and ranged from approximately 5705 to 88,410 ng/mL. Most importantly, however, all samples that contained amphetamine at > or = 500 ng/mL also contained detectable amounts of this hydroxy metabolite (LOD 10 ng/mL), making it a valuable tool in differentiating use of clobenzorex from illicit amphetamine use.

Administration, Oral↗
PubMed2001

Amphetamine, clobenzorex, and 4-hydroxyclobenzorex levels following multidose administration of clobenzorex.

Clobenzorex (Asenlix) is an anorectic drug used as part of a weight-management program. The drug is metabolized by the body to amphetamine, which is then excreted in the urine, thus causing difficulty in interpretation of amphetamine-positive drug tests. Previous studies have shown that the parent drug and several metabolites are excreted in urine. Clobenzorex itself has been detected for as long as 29 h following administration of a single dose. However, the parent drug was not always detected in samples that contained amphetamine at > or =500 ng/mL, the administrative cutoff for a positive result. Consequently, the parent compound clobenzorex is not ideal for ascertaining whether the drug was the origin of the amphetamine. Several metabolites of clobenzorex have been shown to be detected for a longer period of time than the parent. One of these, a hydroxy metabolite, was shown to be detected for an extended period of time. In a study of urine samples provided following administration of a single 30-mg dose of this drug, 4-hydroxyclobenzorex could be detected for up to 91.5 h. More significantly, that study showed all samples that were positive for amphetamine also contained detectable amounts of 4-hydroxyclobenzorex. This metabolite proved to be easily detected and was typically found at higher levels than amphetamine in urine samples positive for amphetamine long after clobenzorex itself could no longer be detected. The present study analyzed samples from a controlled multidose administration (30 mg of clobenzorex daily for seven days) for the presence of 4-hydroxyclobenzorex. The analytical procedure used acid hydrolysis followed by liquid-liquid extraction and gas chromatographic-mass spectrometric analysis with monitoring of ions at m/z 125, 330, and 364 for 4-hydroxyclobenzorex and its 3-Cl regioisomer, which was used as an internal standard. Peak concentrations of 4-hydroxyclobenzorex ranged from 17,786 to 99,044 ng/mL. Most importantly, this study also found that all samples that contained amphetamine at > or =500 ng/mL also contained detectable amounts of this hydroxy metabolite (LOD 10 ng/mL), making it a valuable tool in differentiating use of clobenzorex from illicit amphetamine use.

Amphetamine↗
PubMed2005

Relation between blood- and urine-amphetamine concentrations in impaired drivers as influenced by urinary pH and creatinine.

Amphetamine undergoes extensive renal excretion and significant amounts are present in urine as the unchanged parent drug. This prompted us to investigate whether a quantitative relationship existed between blood and urine concentrations of amphetamine in the body fluids of drug-impaired drivers apprehended in Sweden, where this stimulant is the major drug of abuse. The relationship between blood and urine concentrations of amphetamine was determined by multivariate analysis with urinary pH and creatinine as predictor variables. Amphetamine was determined in blood and urine by gas chromatography-mass spectrometry with deuterium-labelled internal standards. The concentration of amphetamine in urine was about 200 times greater than the concentration in blood; the mean and median urine/blood ratios were 214 and 160, respectively, with large individual variations. The Pearson correlation coefficient between urine (y) and blood (x) amphetamine was r = 0.53, n = 48, which was statistically highly significant (P < 0.001), although the residual standard deviation (SD) was large (+/- 181 mg/L). The correlation coefficient increased (r = 0.60) when the concentration of amphetamine in urine was normalized for dilution by dividing with the creatinine content. When urinary pH and creatinine were both included as predictor variables, the correlation coefficient was even higher (r = 0.69), now explaining 48% (r2 = 0.48) of the variation in urine-amphetamine concentration. However, the partial regression coefficient for creatinine (53 +/- 28.7) was not statistically significant (t = 1.85, P > 0.05), whereas the corresponding regression coefficient for pH was highly significant and had a negative sign (-102 +/- 32.6, t= -3.12, P < 0.005). Other factors could impact on the urine-blood amphetamine relationship, such as route of administration, pattern of voiding and time elapsed after use of the drug.

Adult↗
PubMed1999

N-oxygenation of amphetamine and methamphetamine by the human flavin-containing monooxygenase (form 3): role in bioactivation and detoxication.

(+)- And (-)-amphetamine and methamphetamine were N-oxygenated by the cDNA expressed adult human flavin-containing monooxygenase form 3 (FMO3), their corresponding hydroxylamines. Two major polymorphic forms of human FMO3 were studied, and the results suggested preferential N-oxygenation by only one of the two enzymes. Chemically synthesized (+/-)-amphetamine hydroxylamine was also a substrate for the human FMO3 and it was converted to phenylpropanone oxime with a stereoselectivity ratio of trans/cis of 5:1. Human FMO3 also N-oxygenated methamphetamine to produce methamphetamine hydroxylamine. Methamphetamine hydroxylamine was also N-oxygenated by human FMO3, and the ultimate product observed was phenylpropanone. For amphetamine hydroxylamine, studies of the biochemical mechanism of product formation were consistent with the production of an N, N-dioxygenated intermediate that lead to phenylpropanone oxime. This was supported by the observation that alpha-deutero (+/-)-amphetamine hydroxylamine gave an inverse kinetic isotope effect on product formation in the presence of human FMO3. For methamphetamine, the data were consistent with a mechanism of human FMO3-mediated N,N-dioxygenation but the immediate product, a nitrone, rapidly hydrolyzed to phenylpropanone. The pharmacological activity of amphetamine hydroxylamine, phenylpropanone oxime, and methamphetamine hydroxylamine were examined for effects at the human dopamine, serotonin, and norepinephrine transporters. Amphetamine hydroxylamine and methamphetamine hydroxylamine were apparent substrates for the human biogenic amine transporters but phenylpropanone oxime was not. Presumably, phenylpropanone oxime or nitrone formation from amphetamine and methamphetamine, respectively, represents a detoxication process. Because of the potential toxic nature of amphetamine hydroxylamine and methamphetamine hydroxylamine metabolites and the polymorphic nature of N-oxygenation, human FMO3-mediated metabolism of amphetamine or methamphetamine may have clinical consequences.

Amphetamine↗
PubMed1999

Stability of [123I]IBZM SPECT measurement of amphetamine-induced striatal dopamine release in humans.

Binding competition between endogenous dopamine (DA) and the D2 receptor radiotracer [123I]IBZM allows measurement of the change in synaptic DA following amphetamine challenge with SPECT in the living human brain. Previous investigations using this technique in healthy subjects have shown that the magnitude of amphetamine effect on [123I]IBZM binding potential (BP) is small (range between 5 to 15% decrease), and that a large between-subject variability in this effect is observed. Therefore, it was unclear how much of the apparent between-subject variability was due to a low signal-to-noise ratio in the measurement, vs. true between-subject differences in the magnitude of the response. The goals of this investigation were to test the within-subject reproducibility and reliability of amphetamine-induced decrease in [123I]IBZM BP with a test/retest paradigm, and to establish the presence or absence of tolerance or sensitization to single administration ofi.v. amphetamine. Six healthy male subjects, never previously exposed to psychostimulants, twice underwent measurement of striatal amphetamine-induced DA release (between-measurement interval 16 +/- 10 days) using SPECT and the [123I]IBZM constant infusion technique. Results demonstrated an excellent within-subject reproducibility of amphetamine-induced DA release: amphetamine-induced decreases in [123I]IBZM BP were significant on each day, and had an intraclass correlation coefficient (ICC) of 0.89. Moreover, values from the second experiment were not significantly different from first experiment, suggesting the absence of either sensitization or tolerance to the effect of amphetamine on DA release in these experimental conditions. The subjective activation, as rated by the subjects on analog scales, was also highly reproducible. In conclusion, this scanning technique provides a reliable measurement of amphetamine-induced reduction of [123I]IBZM BP and enables detection of between-subject differences that appear stable over time.

Adult↗