INFLUENCE OF URINARY PH ON EXCRETION OF AMPHETAMINE

The Pharmacokinetics and Pharmacogenomics of Psychostimulants

The psychostimulants-amphetamine and methylphenidate-have been in clinical use for well more than 60 years. In general, both stimulants are rapidly absorbed with relatively poor bioavailability and short half-lives. The pharmacokinetics of both stimulants are generally linear and dose proportional although substantial interindividual variability in pharmacokinetics is in evidence. Amphetamine (AMP) is highly metabolized by several oxidative enzymes forming multiple metabolites while methylphenidate (MPH) is primarily metabolized by hydrolysis to the inactive metabolite ritalinic acid. At present, pharmacogenomic testing as an aid to guide dosing and personalized treatment cannot be recommended for either agent. Few pharmacokinetically based drug-drug interactions (DDIs) have been documented for either stimulant.

What the lab can and cannot do: clinical interpretation of drug testing results

Urine drug testing is one of the objective tools available to assess adherence. To monitor adherence, quantitative urinary results can assist in differentiating "new" drug use from "previous" (historical) drug use. "Spikes" in urinary concentration can assist in identifying patterns of drug use. Coupled chromatographic-mass spectrometric methods are capable of identifying very small amounts of analyte and can make clinical interpretation rather challenging, specifically for drugs that have a longer half-life. Polypharmacy is common in treatment and rehabilitation programs because of co-morbidities. Medications prescribed for comorbidities can cause drug-drug interaction and phenoconversion of genotypic extensive metabolizers into phenotypic poor metabolizers of the treatment drug. This can have significant impact on both pharmacokinetic (PK) and pharmacodynamic properties of the treatment drug. Therapeutic drug monitoring (TDM) coupled with PKs can assist in interpreting the effects of phenoconversion. TDM-PKs reflects the cumulative effects of pathophysiological changes in the patient as well as drug-drug interactions and should be considered for treatment medications/drugs used to manage pain and treat substance abuse. Since only a few enzyme immunoassays for TDM are available, this is a unique opportunity for clinical laboratory scientists to develop TDM-PK protocols that can have a significant impact on patient care and personalized medicine. Interpretation of drug screening results should be done with caution while considering pharmacological properties and the presence or absence of the parent drug and its metabolites. The objective of this manuscript is to review and address the variables that influence interpretation of different drugs analyzed from a rehabilitation and treatment programs perspective.

DARK Classics in Chemical Neuroscience: Methamphetamine

Methamphetamine has the second highest prevalence of drug abuse after cannabis, with estimates of 35 million users worldwide. The ( S)-(+)-enantiomer is the illicit drug, active neurostimulant, and eutomer, while the ( R)-(-)-enantiomer is contained in over the counter decongestants. While designated a schedule II drug in 1970, ( S)-(+)-methamphetamine is available by prescription for the treatment of attention-deficit disorder and obesity. The illicit use of ( S)-(+)-methamphetamine results in the sudden "rush" of stimulation to the motivation, movement, pleasure, and reward centers in the brain, caused by rapid release of dopamine. In this review, we will provide an overview of the synthesis, pharmacology, adverse effects, and drug metabolism of this widely abused psychostimulant that distinguish it as a DARK classic in Chemical Neuroscience.

The Clinical Pharmacokinetics of Amphetamines Utilized in the Treatment of Attention-Deficit/Hyperactivity Disorder

Amphetamine (AMP), an indirectly acting psychostimulant approved for the treatment of attention-deficit/hyperactivity disorder (ADHD) in children, adolescents, and adults, is among the most long-standing therapeutic agents in all of clinical psychopharmacology. This review focuses on AMP absorption, metabolism, and elimination brought to bear on comparative pharmacokinetics in its various formulations. A comprehensive search of the published literature was conducted using MEDLINE (PubMed) and Google Scholar databases through April 2017 to retrieve all pertinent in vitro and human studies for review and synthesis. Additionally, Food and Drug Administration (FDA) databases were accessed for otherwise unavailable data when possible. Initially available as racemic (dl)-AMP, this drug was later supplanted by enantiopure (d)-AMPH or enantioenriched (75:25 dl)-AMP formulations; although racemic AMP returned as an approved drug to treat ADHD in 2014. Presently, there are several immediate-release (IR) formulations available, including d-AMP, dl-AMP, and mixed amphetamine salts, which are neither racemic nor the pure d-enantiomer (i.e., a 3:1 mixture of d-AMP and l-AMP). Furthermore, new modified-release AMP formulations, including an oral suspension and an orally disintegrating tablet, are now available. A lysine-bonded prodrug form of d-AMP also serves as a treatment option. Oral AMP is rapidly absorbed, with high absolute bioavailability, followed by extensive metabolism involving multiple enzymes. Some metabolic pathways exhibit stereoselective biotransformations favoring the l-isomer substrate. Drug exposure exhibits dose-proportional pharmacokinetics. Body weight is a fundamental determinant of differences in observed AMP plasma concentrations. IR formulations typically provide a T_max from 2 to 3 hours. In replicated studies, children exhibit a shorter plasma T_1/2 (∼7 hours) relative to adults (∼10 to 12 hours). There are few documented pharmacokinetic drug interactions of clinical significance beyond influences of drug-induced alteration of urinary pH. The array of AMP formulations addressed in this review offer flexibility in dosing, drug onset, and offset to assist in individualized pharmacotherapy of ADHD.

The influence of urinary pH on the elimination of mexiletine

1 The plasma elimination half-life of mexiletine was measured in four subjects when the urine was rendered (a) acidic and (b) alkaline. 2 Urinary acidification (pH 5.0) was associated with a plasma elimination half-life of 2.8 h and 57.5% of the intravenous dose was excreted in the urine within 48 hours. When the urine was alkaline (pH 8.0) the half-life increased to 8.6 h with negligible amounts of drug appearing in the urine. 3 Urinary pH varies widely in cardiac patients and should be controlled or monitored to provide better therapeutic precision with mexiletine.

Sewer epidemiology mass balances for assessing the illicit use of methamphetamine, amphetamine and tetrahydrocannabinol

In sewer epidemiology, mass balances are used to back-extrapolate measurements of wastewater influent concentrations of appropriate drug residues to assess the parent illicit drug's level of use in upstream populations. This study focussed on developing and refining mass balances for the use of illicit methamphetamine, amphetamine and tetrahydrocannabinol. As a first step, a multi-criteria evaluation was used to select unchanged methamphetamine, unchanged amphetamine and 11-nor-9-carboxy-tetrahydrocannabinol as the most appropriate drug residues to track a selected population's use of illicit methamphetamine, amphetamine and tetrahydrocannabinol, respectively. For each of these selected drug residues, mass balances were developed by utilizing all disposition data available for their release from all their respective sources, incorporating route-of-administration considerations where relevant, and accounting for variations in the metabolic capacity of users of the various relevant licit and illicit sources. Further, since the selected drug residues for the use of methamphetamine and amphetamine cannot only result from their use but numerous other licit and illicit sources, comprehensive general source models were developed for their enantiomeric-specific release to sewers. The relative importance of the sources identified in the general source model was evaluated by performing national substance flow analyses for a number of countries. Results suggested that licit sources of methamphetamine are expected to be only of significance in populations where its illicit use is minor. Similarly, in populations where the use of illicitly produced amphetamine is currently of relevance, licit contributions to the sewer loads of amphetamine are likely to be of negligible importance. Lastly, the study of tetrahydrocannabinol back-extrapolation mass balances suggested that further research is required to assess the importance of fecal elimination of 11-nor-9-carboxy-tetrahydrocannabinol.

Urinary excretion kinetics of methylamphetamine in man

The urinary excretion of methylamphetamine and its metabolite, amphetamine, was studied after oral administration of (+)- and (–)-methylamphetamine hydrochloride to three male subjects. Fluctuations in the excretion rate of both amines occurred and were associated with changes in urinary pH. The fluctuations were abolished when the urine was maintained either acid or alkaline, by administration of ammonium chloride and sodium bicarbonate respectively. The total amount of both amines excreted was lower under alkaline than acid urine conditions. N-Demethylation of methylamphetamine was small, but greater for the (+)- than the (–)-isomer.

Urinary MDMA, MDA, HMMA, and HMA excretion following controlled MDMA administration to humans

3,4-Methylenedioxymethamphetamine (MDMA), or ecstasy, is excreted as unchanged drug, 3,4-methylenedioxyamphetamine (MDA), and free and glucuronidated/sulfated 4-hydroxy-3-methoxymethamphetamine (HMMA), and 4-hydroxy-3-methoxyamphetamine (HMA) metabolites. The aim of this paper is to describe the pattern and timeframe of excretion of MDMA and its metabolites in urine. Placebo, 1.0 mg/kg, and 1.6 mg/kg oral MDMA doses were administered double-blind to healthy adult MDMA users on a monitored research unit. All urine was collected, aliquots were hydrolyzed, and analytes quantified by gas chromatography-mass spectrometry. Median C(max), T(max), ratios, first and last detection times, and detection rates were determined. Sixteen participants provided 916 urine specimens. After 1.6 mg/kg, median C(max) were 21,470 (MDMA), 2229 (MDA), 20,793 (HMMA), and 876 ng/mL (HMA) at median T(max) of 13.9, 23.0, 9.2 and 23.3 h. In the first 24 h, 30.2-34.3% total urinary excretion occurred. HMMA last detection exceeded MDMA's by more than 33 h after both doses. Identification of HMMA as well as MDMA increased the ability to identify positive specimens but required hydrolysis. These MDMA, MDA, HMMA, and HMA pharmacokinetic data may be useful for interpreting workplace, drug treatment, criminal justice, and military urine drug tests. Measurement of urinary HMMA provides the longest detection of MDMA exposure yet is not included in routine monitoring procedures.

Influences of urinary pH on the pharmacokinetics of three amphetamine-type stimulants using a new high-performance liquid chromatographic method

A simple and sensitive high-performance liquid chromatographic (HPLC) method after precolumn derivatization with 9,10-anthraquinone-2-sulfonyl chloride (ASC) has been developed and validated for the analysis of amphetamine-type stimulants (ATS) in biological samples. Based on this method, we investigated the impact of urinary pH on the pharmacokinetics of phenylpropanolamine (PPA), pseudoephedrine (PSE), and fenfluramine (FEN) in rats. The drugs were orally administrated to rats, which had been induced, by repeated oral doses of ammonium chloride or sodium bicarbonate, to excrete urine at lower or higher pH than the normal value, respectively. Results revealed that as the increase of urinary pH, the mean elimination half-life (t(1/2)), the mean residence time (MRT) and the area under the plasma concentration-time curve (AUC) of PPA, PSE, and FEN were greatly raised, while the total plasma clearance (CL/F) decreased considerably. These findings have important clinical implications.

Treatment for amphetamine psychosis

BACKGROUND

Chronic amphetamine users may have experience of paranoia and hallucination. It has long been believed that dopamine antagonists, such as chlorpromazine, haloperidol, and thioridazine, are effective for the treatment of amphetamine psychosis.

OBJECTIVES

To evaluate risks, benefits, costs of treatments for amphetamine psychosis.

SEARCH STRATEGY

MEDLINE (1966-2007), EMBASE (1980-2007), CINAHL (1982-2007), PsychINFO (1806-2007), CENTRAL (Cochrane Library 2008 issue 1), references of obtained articles.

SELECTION CRITERIA

All randomised controlled and clinical trials (RCTs, CCTs) evaluating treatments (alone or combined) for people with amphetamine psychosis

DATA COLLECTION AND ANALYSIS

Two authors evaluated and extracted the data independently. Dichotomous data were extracted on an intention-to-treat basis in which the dropouts were assigned as participants with the worst outcomes. The Relative Risk (RR) with the 95% confidence interval (95% CI) was used to assess the dichotomous data. The Weighted Mean Difference (WMD) with 95% CI was used to assess the continuous data.

MAIN RESULTS

The comprehensive searches found one randomised controlled trial of treatment for amphetamine psychosis meeting the criteria for considering studies. The study involved 58 participants and compared the efficacy and tolerability of two antipsychotic drugs, olanzapine (a newer antipsychotic) and haloperidol (a commonly used antipsychotic medication used as a control condition), in treating amphetamine-induced psychosis. The results show that both olanzapine and haloperidol at clinically relevant doses were efficacious in resolving psychotic symptoms, with the olanzapine condition showing significantly greater safety and tolerability than the haloperidol control as measured by frequency and severity of extrapyramidal symptoms.

AUTHORS' CONCLUSIONS

Only one RCT of treatment for amphetamine psychosis has been published. Outcomes from this trial indicate that antipsychotic medications effectively reduce symptoms of amphetamine psychosis, the newer generation and more expensive antipsychotic medication, olanzapine, demonstrates significantly better tolerability than the more affordable and commonly used medication, haloperidol.There are other two studies that did not meet the inclusion criteria for this review. The results of these two studies show that agitation and some psychotic symptoms may be abated within an hour after antipsychotic injection.Whether this limited evidence can be applied for amphetamine psychotic patients is not yet known.The medications that should be further investigate are conventional antipsychotics, newer antipsychotics and benzodiazepines. However, naturalistic studies of amphetamine psychotic symptoms and the prevalence of relapse to psychosis in the presence of amphetamine, are also crucial for advising the development of study designs appropriate for further treatment studies of amphetamine psychosis.

Treatment for amphetamine psychosis

BACKGROUND

Chronic amphetamine users may have experience of paranoia and hallucination. It has long been believed that dopamine antagonists, such as chlorpromazine, haloperidol, and thioridazine, are effective for the treatment of amphetamine psychosis.

OBJECTIVES

To evaluate risks, benefits, costs of treatments for amphetamine psychosis.

SEARCH STRATEGY

MEDLINE (1966-2007), EMBASE (1980-2007), CINAHL (1982-2007), PsychINFO (1806-2007), CENTRAL (Cochrane Library 2008 issue 1), references of obtained articles.

SELECTION CRITERIA

All randomised controlled and clinical trials (RCTs, CCTs) evaluating treatments (alone or combined) for people with amphetamine psychosis

DATA COLLECTION AND ANALYSIS

Two authors evaluated and extracted the data independently. Dichotomous data were extracted on an intention-to-treat basis in which the dropouts were assigned as participants with the worst outcomes. The Relative Risk (RR) with the 95% confidence interval (95% CI) was used to assess the dichotomous data. The Weighted Mean Difference (WMD) with 95% CI was used to assess the continuous data.

MAIN RESULTS

The comprehensive searches found one randomised controlled trial of treatment for amphetamine psychosis meeting the criteria for considering studies. The study involved 58 participants and compared the efficacy and tolerability of two antipsychotic drugs, olanzapine (a newer antipsychotic) and haloperidol (a commonly used antipsychotic medication used as a control condition), in treating amphetamine-induced psychosis. The results show that both olanzapine and haloperidol at clinically relevant doses were efficacious in resolving psychotic symptoms, with the olanzapine condition showing significantly greater safety and tolerability than the haloperidol control as measured by frequency and severity of extrapyramidal symptoms.

AUTHORS' CONCLUSIONS

Only one RCT of treatment for amphetamine psychosis has been published. Outcomes from this trial indicate that antipsychotic medications effectively reduce symptoms of amphetamine psychosis, the newer generation and more expensive antipsychotic medication, olanzapine, demonstrates significantly better tolerability than the more affordable and commonly used medication, haloperidol.There are other two studies that did not meet the inclusion criteria for this review. The results of these two studies show that agitation and some psychotic symptoms may be abated within an hour after antipsychotic injection. Whether this limited evidence can be applied for amphetamine psychotic patients is not yet known.The medications that should be further investigate are conventional antipsychotics, newer antipsychotics and benzodiazepines. However, naturalistic studies of amphetamine psychotic symptoms and the prevalence of relapse to psychosis in the presence of amphetamine, are also crucial for advising the development of study designs appropriate for further treatment studies of amphetamine psychosis.

Clinical pharmacokinetics of amfetamine and related substances: monitoring in conventional and non-conventional matrices

Consumption of amfetamine-type stimulants, including classical amfetamines and 'designer drugs', has been recognised as one of the most significant trends in drug abuse at the end of the past century and at the beginning of the current one. The first cause is the increasing consumption amongst youth of methylenedioxy- and methoxy-substituted amfetamines, of which the pharmacology in humans is currently under investigation. Secondly, the abuse of more classical amfetamines, such as amfetamine itself and metamfetamine, continues to be highly prevalent in some geographical regions. Amfetamines are powerful psychostimulants, producing increased alertness, wakefulness, insomnia, energy and self-confidence in association with decreased fatigue and appetite as well as enhanced mood, well-being and euphoria. From a clinical pharmacokinetic perspective, amfetamine-type stimulants are rather homogeneous. Their oral bioavailability is good, with a high distribution volume (4 L/kg) and low binding to plasma proteins (less than 20%). The elimination half-life is 6-12 hours. Both hepatic and renal clearance contribute to their elimination from the body. Hepatic metabolism is extensive in most cases, but a significant percentage of the drug always remains unaltered. Amfetamine and related compounds are weak bases, with a pKa around 9.9, and a relatively low molecular weight. These characteristics allow amfetamine-type stimulants to diffuse easily across cell membranes and lipid layers and to those tissues or biological substrates with a more acidic pH than blood, facilitating their detection in alternative matrices at relatively high concentrations. In most cases, the concentrations found are higher than expected from the Henderson-Hasselbach equation. Drug monitoring in non-conventional biological matrices (e.g. saliva, hair, nails, sweat) has recently gained much attention because of its possible applications in clinical and forensic toxicology. An individual's past history of medication, compliance or drug abuse can be obtained from testing of hair and nails, whereas data on current status of drug use can be provided by analysis of sweat and saliva. Because of the physicochemical properties of amfetamine-type stimulants, this group of drugs is one of the most suitable for drug testing in non-conventional matrices.

Malaria and amphetamine 'horse tablets' in Thailand

During recent clinical malaria research in Thailand we found a high frequency of amphetamine misuse and withdrawal amongst patients admitted to hospital with Plasmodium falciparum malaria. This comorbidity may cause diagnostic confusion, alter malaria pathophysiology and lead to drug interactions.

Pharmacokinetic and pharmacodynamic drug interactions in the treatment of attention-deficit hyperactivity disorder

The psychostimulants methylphenidate, amphetamine and pemoline are among the most common medications used today in child and adolescent psychiatry for the treatment of patients with attention-deficit hyperactivity disorder. Frequently, these medications are used in combination with other medications on a short or long term basis. The present review examines psychostimulant pharmacology, summarises reported drug-drug interactions and explores underlying pharmacokinetic and pharmacodynamic considerations for interactions. A computerised search was undertaken using Medline (1966 to 2000) and Current Contents to provide the literature base for reports of drug-drug interactions involving psychostimulants. These leads were further cross-referenced for completeness of the survey. Methylphenidate appears to be more often implicated in pharmacokinetic interactions suggestive of possible metabolic inhibition, although the mechanisms still remain unclear. Amphetamine was more often involved in apparent pharmacodynamic interactions and could potentially be influenced by medications affecting cytochrome P450 (CYP) 2D6. No published reports of drug interactions involving pemoline were found. The alpha2-adrenergic agonists clonidine and guanfacine have been implicated in several interactions. Perhaps best documented is their antagonism by tricyclic antidepressants and phenothiazines. In additional, concurrent beta-blocker use, or abrupt discontinuation, can lead to hypertensive response. Although there are few published well-controlled interaction studies with psychostimulants and alpha2-adrenergic agonists, it appears that these agents may be safely coadministered. The interactions of monoamine oxidase inhibitors with psychostimulants represent one of the few strict contraindications.

Effect of gender, sex hormones, time variables and physiological urinary pH on apparent CYP2D6 activity as assessed by metabolic ratios of marker substrates

The effects of gender, time variables, menstrual cycle phases, plasma sex hormone concentrations and physiologic urinary pH on CYP2D6 phenotyping were studied using two widely employed CYP2D6 probe drugs, namely dextromethorphan and metoprolol. Phenotyping on a single occasion of 150 young, healthy, drug-free women and men revealed that the dextromethorphan: dextrorphan metabolic ratio (MR) was significantly lower (P < 0.0001) in 56 female extensive metabolizers (0.008+/-0.021) compared to 86 male extensive metabolizers (0.020 +/-0.040). Urinary pH was a significant predictor of dextromethorphan: dextrorphan MRs in men and women (P < 0.001). Once-a-month phenotyping with dextromethorphan of 12 healthy young men (eight extensive metabolizers and four poor metabolizers) over a 1-year period, as well as every-other-day phenotyping with dextromethorphan of healthy, pre-menopausal women (10 extensive metabolizers and 2 poor metabolizers) during a complete menstrual cycle, did not follow a particular pattern and showed similar intrasubject variability ranging from 24.1% to 74.5% (mean 50.9%) in men and from 20.5% to 96.2% (mean 52.0%) in women, independent of the CYP2D6 phenotype (P = 0.342). Using metoprolol as a probe drug, considerable intrasubject variability (38.6+/- 12.0%) but no correlation between metoprolol: alpha-hydroxymetoprolol MRs and pre-ovulatory, ovulatory and luteal phases (mean +/- SD metoprolol: a-hydroxymetoprolol MRs: 1.086+/- 1.137 pre-ovulatory; 1.159+/-1.158 ovulatory and 1.002+/-1.405 luteal phase; P> 0.9) or 17beta-oestradiol, progesterone or testosterone plasma concentrations was observed. There was a significant inverse relationship between physiologic urinary pH and sequential dextromethorphan: dextrorphan MRs as well as metoprolol: alpha-hydroxymetoprolol MRs in men and women, with metabolic ratios varying up to six-fold with metoprolol and up to 20-fold with dextromethorphan (ANCOVA P < 0.001). We conclude that apparent CYP2D6 activity is highly variable, independent of menstrual cycle phases, sex hormones, time variables or phenotype. Up to 80% of the observed variability can be explained by variations of urinary pH within the physiological range. An apparent phenotype shift as a result of variations in urinary pH may be observed in individuals who have metabolic ratios close to the population antimode.

Illegal or legitimate use? Precursor compounds to amphetamine and methamphetamine

The interpretation of methamphetamine and amphetamine positive test results in biological samples is a challenge to clinical and forensic toxicology for several reasons. The effects of pH and dilution of urine samples and the knowledge about legitimate and illicit sources have to be taken into account. Besides a potentially legal prescription of amphetamines, many substances metabolize to methamphetamine or amphetamine in the body: amphetaminil, benzphetamine, clobenzorex, deprenyl, dimethylamphetamine, ethylamphetamine, famprofazone, fencamine, fenethylline, fenproporex, furfenorex, mefenorex, mesocarb, and prenylamine. Especially the knowledge of potential origins of methamphetamine and amphetamine turns out to be very important to prevent a misinterpretation of the surrounding circumstances and to prove illegal drug abuse. In this review, potential precursor compounds are described, including their medical use and major clinical effects and their metabolic profiles, as well as some clues which help to identify the sources.

Testing for drugs of abuse in saliva and sweat

The detection of marijuana, cocaine, opiates, amphetamines, benzodiazepines, barbiturates, PCP, alcohol and nicotine in saliva and sweat is reviewed, with emphasis on forensic applications. The short window of detection and lower levels of drugs present compared to levels found in urine limits the applications of sweat and saliva screening for drug use determination. However, these matrices may be applicable for use in driving while intoxicated and surveying populations for illicit drug use. Although not an illicit drug, the detection of ethanol is reviewed because of its importance in driving under the influence. Only with alcohol may saliva be used to estimate blood levels and the degree of impairment because of the problems with oral contamination and drug concentrations varying depending upon how the saliva is obtained. The detection of nicotine and cotinine (from smoking tobacco) is also covered because of its use in life insurance screening and surveying for passive exposure.

Salt intake determines the renal response to L-arginine infusion in normal human subjects

Studies in experimental animals have shown that nitric oxide (NO) generation in the kidney from L-arginine participates in adapting renal function to changes in salt intake, but similar studies in human subjects are lacking. Therefore, we compared the infusion of 30 g of L-arginine to 30 g of branched chain amino acids (control), in eight normal human subjects after 5 to 7 days of equilibration to a low salt (LS; 20 mumol.24 hr-1) or high salt (HS; 200 mumol.24 hr-1) intake. Lithium clearance was used as a marker of proximal tubular reabsorption. Compared to the control infusion, L-arginine did not significantly alter blood pressure, inulin or paraaminohippurate clearance, but significantly increased (P < 0.05) the excretion of NO2 + NO3 (NOx) (LS, 157 +/- 46 to 210 +/- 48 mumol.min-1; HS, 138 +/- 30 to 182 +/- 70) and cGMP (LS, 253 +/- 63 to 337 +/- 76 pmol.min-1; HS, 311 +/- 68 to 563 +/- 52). Renal sodium excretion was decreased by L-arginine infusion during the low salt intake (45 +/- 5 to 21 +/- 3 mumol.min-1; P < 0.05) but was increased by L-arginine during the high salt intake (298 +/- 56 to 537 +/- 84 mumol.min-1; P < 0.05). The calculated fractional reabsorption of sodium in the proximal and distal nephrons, as assessed from lithium and sodium clearances, was increased by L-arginine during the low salt intake but was decreased by L-arginine during the high salt intake. L-arginine increased plasma insulin concentration significantly (P < 0.05). This effect was independent of salt intake (LS, 67 +/- 7 to 92 +/- 13 ng.ml-1; HS, 66 +/- 7 to 76 +/- 9 ng.ml-1). L-arginine did not significantly after plasma renin activity. In conclusion, L-arginine increases the excretion of NOx and cGMP and increases plasma insulin, but the effect on sodium excretion depends upon salt intake. L-arginine enhances Na reabsorption in the proximal and distal nephrons during the low salt intake, but inhibits it during the high salt intake. Effects of L-arginine on NO and cGMP may contribute to its effects on Na reabsorption.

Stimulants, narcotics and beta-blockers: 25 years of development in analytical techniques for doping control

More than 25 years of developing doping control methods have led to comprehensive screening and confirmation procedures for stimulants, narcotics and beta-blockers. Much of this work has been initiated and/or improved by the late Prof. Dr. Manfred Donike. The methodological approach covered in this overview was applied to doping control procedures during the XXV Summer Olympics in Barcelona, Spain, in 1992 and the XVII Winter Olympics in Lillehammer, Norway, in 1994. Urine samples are screened through a combination of two analytical methods that are complementary: (a) gas chromatographic analysis of the parent compound and unconjugated metabolites, following single-step sample extraction and detection by a nitrogen-specific detector based on a retention index identification system and (b) gas chromatographic analysis including also conjugated drugs and metabolites after hydrolysis, solid-phase extraction, derivatisation and mass spectrometric detection. Confirmation and identification is always performed by gas chromatographic separation and full scan mass spectrometric detection. These methods facilitate the rapid screening and confirmation of more than 100 stimulants, narcotic analgesics and beta-blockers in urine for at least 24 h after the intake of a pharmaceutical dose. Application of the methods ensures high quality standards for the unequivocal identification of doping agents as well as a rapid turnaround time for sample analyses.

Chronopharmacokinetics and chronopharmacodynamics of dextromethamphetamine in man

Stimulants, in particular the amphetamines, have been studied as countermeasures to fatigue induced by circadian desynchronosis and extended flight operations. To make recommendations concerning the use of dextromethamphetamine for operational tasks, its chronopharmacokinetic and chronopharmacodynamic profiles and influence on circadian rhythms as a countermeasure to performance deficits and fatigue were studied. Ten male volunteers, divided into two groups of five each, were given 30 mg/70 kg of oral dextromethamphetamine during two test sessions one week apart and were evaluated with cognitive (dichotic listening, pattern recognition, and compensatory tracking), subjective (fatigue scale), and physiologic (blood pressure) testing. Session order was counterbalanced with dextromethamphetamine administration at either 8:40 AM or 8:40 PM during session one and a crossover to the other time during session two. Subjective and cognitive testing was begun 1.5 hours before dextromethamphetamine administration and continued every half hour until 12.5 hours after administration. Blood pressure was measured immediately before behavioral testing. Serum and urine were collected at regular intervals for gas chromatography/mass spectrometer analysis of methamphetamine and one of its metabolites, amphetamine. No differences were found in the day-versus-night pharmacokinetic profile of dextromethamphetamine. Cognitive performance and subjective fatigue improved after daytime administration of dextromethamphetamine in comparison to performance before drug administration. This effect was suppressed during the circadian trough, which occurred approximately 8 hours into the night sessions (4:30 AM). No correlations were seen between serum concentration of methamphetamine and measured behavioral parameters.

Urinary excretion of p-hydroxylated methamphetamine metabolites in man. II. Effect of alcohol intake on methamphetamine metabolism

The effect of drinking alcoholic beverages on methamphetamine metabolism was investigated in man. The subjects, 97 males and 9 females, were divided into three groups by evaluation of their urinary pH; i.e., acidic, subacidic and neutral groups. The subjects in each group were further divided into ethanol-positive subjects and ethanol-negative subjects, depending on the presence or absence of ethanol in their urine. Gas chromatographic analysis showed the urinary concentrations of methamphetamine in the ethanol-positive subjects to be higher than those in the ethanol-negative subjects in both the acidic and subacidic urinary pH groups. Liquid chromatography, on the other hand, showed the urinary concentrations of p-hydroxymethamphetamine and p-hydroxyamphetamine for the ethanol-positive subjects to be lower than those for the ethanol-negative subjects in all three groups. The relative proportions of p-hydroxylated metabolites to unchanged methamphetamine in urine, therefore, were severely reduced in the ethanol-positive subjects. These results suggest that drinking alcoholic beverages probably results in a suppression of methamphetamine metabolism in man.

Amphetamine, mazindol, and fencamfamin in narcolepsy

Twenty patients with the narcoleptic syndrome were treated separately with dexamphetamine sulphate tablets 10 and 30 mg, Dexedrine Spansules 10 mg, mazindol 4 mg, and fencamfamin hydrochloride 60 mg daily. Each drug was given for four weeks and the effects compared. In these dosages the reported frequency of attacks of narcolepsy was roughly halved with each treatment, dexamphetamine 30 mg daily being only slightly more potent than 10 mg. The subjective effects of Dexedrine tablets and Spansules could not be distinguished by most patients. Effects on mood, alertness, and sympathomimetic side effects were largely inseparable with all these drugs, but a decrease in appetite was not reported by patients with narcolepsy.

Circadian rhythm of urinary pH in man with and without chronic antacid administration

In normal human volunteers, when urinary pH was plotted versus time, the circadian sine-wave type curve was not altered by chronic administration of a commercially available suspension containing a mixture of magnesium and aluminum hydroxides, although the antacid perturbed the entire curve in a more alkaline direction. A single dose of the antacid had little effect on urinary pH. There was a highly significant linear relationship between the change in hydrogen ion concentration during chronic antacid treatment and the initial control urinary hydrogen ion concentration, but there was no significant correlation between change in urinary pH and initial control urinary pH as has been previously reported. The above results were based on the evaluation of the hydrogen ion concentrations of 1562 separate urine samples collected from 24 normal subjects in a three treatment crossover study. It is recommended that: (1) research studies involving drug-drug interactions with antacids be designed to consider the effect of the antacid on the circadian rhythm of urinary pH, and (2) pH values not be averaged as commonly reported in the literature, but rather the pH values be converted to hydrogen ion concentrations before statistical analysis.

Amphetamines, growth hormone and narcolepsy

1 Plasma amphetamine and growth hormone levels have been measured in eight normal and twenty-six narcoleptic subjects following a single dose of (+)-amphetamine (20 mg) or (-)-amphetamine (20 mg) by mouth. 2 Peak plasma levels and the shape of the plasma amphetamine-time curve were similar with both isomers in normal and narcoleptic subjects. 3 In most normal subjects both (+)-and (-)-amphetamine (20 mg) caused an increase in the plasma concentration of growth hormone. The two isomers were approximately equipotent in this respect. Neither (+)- nor (-)-amphetamine (20 mg) caused an increase in plasma growth hormone concentration in narcoleptics. 4 Following amphetamine (30 mg), two of six narcoleptic subjects had an increase in plasma growth hormone concentration. 5 Levodopa (250 mg) with (-)-alpha-methyldopa hydrazine 25 mg (Sinemet) by mouth, caused a rise in plasma growth hormone concentration in most normal subjects. The magnitude of the Sinemet-induced rise in plasma growth hormone concentration in narcoleptics was less than in normal subjects.

The biochemistry of affective disorders

The title of this review would be regarded by some psychiatrists as provocative; they would relegate the biochemical concomitants of depression and mania to a secondary position and deny that biochemical changes have any place in the aetiology of these conditions. However, in my view, the weight of evidence, although it is by no means conclusive, suggests that biochemical changes are most important in the aetiology of affective disorders. A biochemical aetiology implies that there are certain biochemical changes in the brain which need to be restored to normal before the patient's clinical condition will improve. This does not deny that psychological and environmental events may precipitate and maintain the biochemical events which in turn lead to the affective disorder. The study of these biochemical events is clearly at too early a stage for speculations about the interrelationship between environmental and endogenous elements to be fruitful; this study must wait until the biochemical aetiology is clearer than at present.