Isotope-dilution mass spectrometric quantification of the prodrug lisdexamfetamine in human urine in doping control analysis

RATIONALE

Therapeutic approaches concerning attention-deficit hyperactivity disorder (ADHD) commonly include the administration of drugs amplifying cerebral dopamine and norepinephrine signals. Among these, compounds belonging to the Prohibited List as established by the World Anti-Doping Agency (WADA) are present such as amfetamine or methylphenidate, and abuse of these can result in sanctions for athletes. The recently approved therapeutic lisdexamfetamine represents a slow-release prodrug of amfetamine for ADHD treatment. In order to support doping control laboratories in differentiating the abuse of amfetamine from a therapeutic administration of lisdexamfetamine, the determination of the prodrug from urine is desirable. Since approximately 2% of lisdexamfetamine are eliminated intact into urine, a liquid chromatography/high-resolution/high accuracy mass spectrometric method was developed, allowing the target analyte and one of its metabolites (4-hydroxyamfetamine sulfate) to be accurately quantified.

METHODS

Urine samples were fortified with fourfold deuterated lisdexamfetamine and analyzed directly using ultrahigh-performance liquid chromatography (UHPLC) interfaced via electrospray ionization to a second-generation quadrupole-orbitrap mass spectrometer. The assay was characterized concerning specificity, limits of quantification (0.15-5 ng/mL), intraday and interday imprecision (4-22%), accuracy (90-120%), linearity, and ion suppression/enhancement effects. A patient's urine samples were analyzed to provide proof-of-principle data demonstrating that the intact prodrug lisdexamfetamine is detectable in urine up to 11 h post-administration at concentrations up to 80 ng/mL. Moreover, amfetamine and sulfoconjugated 4-hydroxyamfetamine were measured, yielding up to 1146 and 56 ng/mL, respectively.

CONCLUSIONS

Considering the observed comparably low urinary concentrations of lisdexamfetamine and 4-hydroxyamfetamine sulfate, the preferred minimally labor-intense sample preparation, and the necessity of fast and robust result generation, the employed instrumental setup proved fit-for-purpose in sports drug testing.

Simultaneous determination of amphetamine and methamphetamine enantiomers in urine by simultaneous liquid–liquid extraction and diastereomeric derivatization followed by gas chromatographic–isotope dilution mass spectrometry

A simple, rapid, reliable, and economic analytical scheme starting with in situ liquid-liquid extraction and asymmetric (or diastereomeric) chemical derivatization (ChD) followed by gas chromatography (GC)-isotope dilution mass spectrometry (MS) is described for the simultaneous determination of D- and L-amphetamine (AP) and methamphetamine (MA) in urine which could have resulted from the administration of various forms of questioned amphetamines or amphetamines-generating drugs. By using L-N-trifluoroacetyl-1-prolyl chloride (L-TPC) as chiral derivatizing agent, resolutions of 2.2 and 2.0 were achieved for the separation of AP and MA enantiomeric pairs, respectively, on an ordinary HP-5MS capillary column. The GC-MS quantitation was carried out in the selected ion monitoring (SIM) mode using m/z 237 and 251 as the quantifier ions for the respective diastereomeric pairs of AP-L-TPC and MA-L-TPC. The calibration curves plotted for the two pairs of analytes stretch with good linearity down to 45 ng/mL, and the limits of detection and quantitation determined were as low as 40 and 45 ng/mL, respectively. Also, a comparative study using 10 real-case urine specimens previously screened as positive for MA administration showed mostly tolerable biases between the two sums (of concentration) of D- and L-MA obtained via an asymmetric L-TPC-ChD approach and via an ordinary pentafluoropropionylation (PFPA-ChD) approach, respectively, as well as between the two sums of D- and L-AP obtained thereupon, thus validating the proposed analytical scheme as a promising forensic protocol for the detailed analysis of enantiomeric amphetamines in urine.

Amphetamine Excretion Profile Following Multidose Administration of Mixed Salt Amphetamine Preparation

Interpretation of drug testing results requires detailed scientific information, particularly in those cases where the question of legitimate use versus illicit use arises. Amphetamine remains a widely abused drug throughout the world, although it is also used therapeutically for weight loss, narcolepsy, and attention-deficit disorder with hyperactivity (ADHD). Treatment of ADHD using stimulant drugs is much more common now than it was in even the recent past. Increasingly, older individuals are diagnosed and treated for ADHD, and treatment often continues into adulthood. Amphetamine is commonly used for the treatment of ADHD and is available by prescription as either the d-enantiomer or a mixture of enantiomers. Although used for many years, there are no data available to describe the excretion profile of amphetamine and its enantiomers following repeated use of the drug. As a result, medical review officers (MROs) and forensic toxicologists have no direct evidence to base their decisions on when it comes to evaluation of use of these drugs. The current study was designed to determine the concentration and enantiomer excretion profile following repeated daily administration of mixed enantiomers of amphetamine. Twenty milligrams of Adderall was administered daily to five healthy subjects with all subsequent ad lib urine samples collected for at least five days following administration of the five-dose regimen. Adderall is a 3:1 mixture of d- and l-enantiomers of amphetamine salts and represents the mixed enantiomer proportion of amphetamine available in the United States through pharmaceutical channels. Peak amphetamine concentrations ranged from 5739 to 19,172 ng/mL. Samples containing > or = 500 ng/mL amphetamine (the administrative cutoff for a positive result by gas chromatography-mass spectrometry) were seen up to 60:15 (h:min) following administration of the last dose. Enantiomer analysis showed the d-enantiomer to be in excess of the l-enantiomer for as long as the drug was administered. After administration of the last dose of drug, the proportion of l-enantiomer increased over time. Not all samples that contained > or = 500 ng/mL total amphetamine were positive when tested by immunoassay because of the differing cross-reactivity of the enantiomers. This study provides the first description of the excretion of amphetamine following repeated administration of Adderall. The presence of the l-enantiomer separates this drug from other formulations composed of only the d-enantiomer (i.e., Dexedrine and much illicit amphetamine), thus readily differentiating them from Adderall use. Some illicit and medicinal amphetamine is, however, a mixture of amphetamine enantiomers. Because the enantiomers are metabolized at different rates, their proportion offers the opportunity to describe excretion versus time. Coupling this data with drug concentration makes it possible for forensic toxicologists and MROs to come to an informed decision regarding the involvement of this drug in a positive drug test result.

Analytic Performance of Immunoassays for Drugs of Abuse Below Established Cutoff Values

Background: The analytic performance and accuracy of drug detection below Substance Abuse and Mental Health Services Administration (SAMHSA) cutoffs is not well known. In some patient populations, clinically significant concentrations of abused drugs in urine may not be detected when current SAMHSA cutoffs are used. Our objectives were to define the precision profiles of three immunoassay systems for drugs of abuse and to evaluate the accuracy of testing at concentrations at which the CV was <20%.

Methods: Drug-free urine was supplemented with analytes to assess the precision in three commercial drugs-of-abuse immunoassay systems below the SAMHSA-dictated cutoffs for amphetamines, opiates, benzoylecgonine, phencyclidine, and cannabinoids. Consecutive urine samples with signals associated with a CV <20% by Emit® immunoassay and below SAMHSA cutoffs were then subjected to confirmatory analysis.

Results: The CV of all immunoassay systems tested remained <20% to drug concentrations well below SAMHSA cutoffs. The accuracy of urine drug-screening results between the SAMHSA-specified cutoffs and the precision-based cutoffs was less than accuracy for specimens above the SAMHSA cutoffs, but the use of the precision-based cutoff produced a 15.6% increase in the number of screen-positive specimens and a 7.8% increase in the detection of specimens that yielded positive results on confirmatory testing.

Conclusion: The precision of three commercial immunoassay systems for drugs-of-abuse screening is adequate to detect drugs below SAMHSA cutoffs. Knowledge of the positive predictive values of screening immunoassays at lower cutoff concentrations could enable efficient use of confirmatory testing resources and improved detection of illicit drug use.

Dextroamphetamine for cocaine-dependence treatment: a double-blind randomized clinical trial

A properly implemented agonist treatment regimen should improve retention and reduce illicit drug use. Cocaine-dependent subjects (N = 128) were enrolled in a 12-week randomized, double-blind, placebo-controlled trial. In the multistage dosing design, subjects initially received placebo (PBO) or 15 to 30 mg of dextroamphetamine sulfate, sustained-release capsules. At week 5, the dose doubled to 30 mg or 60 mg for active groups. Subjects attended the clinic twice a week, provided urine samples, obtained medication, and had one behavioral therapy session a week. Retention was best for the 15- to 30-mg group, whereas the proportion of benzoylecgonine-positive urine screens was, from lowest to highest, 30 to 60 mg, 15 to 30 mg, and PBO at study end. Dosing must be refined. The results provide support for additional examination of the agonist model in psychostimulant-dependence treatment.

Using amphetamine isomer ratios to determine the compliance of amphetamine abusers prescribed dexedrine

The amphetamine isomer ratios (l-amphetamine/d-amphetamine) in 373 urine specimens submitted for analysis over a two-year period have been determined using a chiral derivatizing agent in conjunction with a gas chromatograph fitted with a nitrogen-specific detector. All of the specimens were collected from known or suspected amphetamine abusers, some of which were prescribed dexedrine for maintenance and detoxification. The mean (+/- 1 standard deviation [SD]) l/d-amphetamine isomer ratio for 147 specimens from compliant subjects prescribed dexedrine was 15.0% (+/- 4.9%). The mean (+/- 1 SD) l/d-amphetamine isomer ratio from 165 subjects abusing illicit amphetamine was 98.5 (+/- 27.5%). The calculation of l/d-amphetamine isomer ratios in urine has been found to be a rapid method for determining the compliance of subjects prescribed dexedrine and is therefore a useful technique for the continued management of amphetamine abusers. In addition, 17 specimens of illicit amphetamine powder (assumed to be a racemic mixture) were submitted to the laboratory for analysis. Using a combination of gas chromatography with and without chiral derivatization, the powders were found to have a mean l/d-amphetamine isomer ratio of 89.2% (range 72.2% to 98.3%) and mean purity (w/w) of 21.5% (range 3.4% to 71.0%) relative to pure dl-amphetamine substance.

Urinary excretion of d-amphetamine following oral doses in humans: implications for urine drug testing

Seven healthy male volunteers received a single oral dose of 5 mg, 10 mg, or 20 mg of d-amphetamine. Urine was collected at 2, 4, 8, 12, 18, and 24 h post-dose. Total urine volume was measured, and pH and creatinine were determined. All specimens were analyzed by TDx Amphetamine/Methamphetamine II (TDx), Emit-d.a.u. Monoclonal Amphetamine/Methamphetamine (EM), and Emit II Amphetamine/Methamphetamine (EII) immunoassays at a cutoff value of 1000-ng/mL amphetamine. Quantitation of urinary amphetamine in all specimens was performed by gas chromatography-mass spectrometry. All urine testing results by the three immunoassays, EM, EII, and TDx, were in agreement; there were no discordant findings. Of the 42 total urine specimens collected following a 5-mg dose of amphetamine, only 8 (19%) screened positive by immunoassay. Twenty-four of 36 (67%) urine specimens yielded positive responses following a 10-mg dose, and 37 of 42 (88%) were positive by immunoassay following a 20-mg dose. These data demonstrate the present guideline for regulated forensic urine drug testing (FUDT) for amphetamine with a screening cutoff of 1000 ng/mL is too high to consistently detect the administration of a single 5-mg oral dose of d-amphetamine. There was considerable overlap of amphetamine concentrations in individual specimens following the various doses. Peak urinary amphetamine ranged from 620 to 3160 ng/mL following 5-mg doses. The time to peak concentration also varied widely at each dose, occurring in urines collected 2 to 18 h post-administration. The mean percent of dose excreted as unchanged amphetamine over 24 h at each dose ranged from 35 to 44%. The data demonstrated that amphetamine excretion increases with increasing urine flow and decreasing urine pH. Thus, a positive FUDT result for amphetamine means only that the individual was administered or self-administered amphetamine at some time prior to collection of the specimen.

Time-lapse changes of d- and l-enantiomers of racemic (dl)-ethylamphetamine in human urine

The time-lapse changes of d- and i-forms in urine specimens collected in the 24 h after the oral dosing of two adult male subjects with 20 mg of racemic (dl)-ethylamphetamine (EAMP)-HCl were examined by high-performance liquid chromatography. The percentage of the excreted dose of nonmetabolized l-EAMP was larger than that of d-EAMP, and the percentage of the excreted dose of metabolized l-amphetamine (AMP) was smaller than that of d-AMP in both subjects, A and B. These differences were observed 4.5-24 h after administration of the drug. The changes in the l/d ratio of EAMP and AMP were not similar between subjects A and B, but the change in the total l/d ratio was nearly the same. The regression line for subject A was as follows: y = 0.021323x + 0.98399. The regression line for subject B was as follows: y = 0.020947x + 0.94893. These two regression lines suggested that the time lapsed after the administration to humans could be predicted. The total percent of the excreted doses of EAMP and AMP was 47.46% (the d-forms, 20.73%; the l-forms, 26.73%) for subject A and was 31.43% (the d-forms, 14.14%; the l-forms, 17.29%) for subject B. The l/d ratio was 1.29 for subject A and 1.22 for subject B, which was somewhat higher than that (1.01) of the dl-EAMP-HCl used.

Two-dimensional gas chromatography for the enantiomeric separation of ephedrine and phenaminum and their metabolites

Two-dimensional gas chromatography was used for enantiomeric separation of ephedrine, phenaminum and their metabolites in human urine. The main column was coated with a 2,6-di-O-pentyl-3-O-trifluoroacetylated-alpha-cyclodextrin and an SE-54 phase column was used as precolumn. The results showed that two-dimensional chromatography could greatly simplify the sample preparation, eliminate the interference of sample matrices, and improve the resolution of the enantiomers of interest.

Chirality of methamphetamine and amphetamine from workplace urine samples

Several positive methamphetamine/amphetamine urine samples were reexamined to determine the chirality of the detected drug or drugs. (S)-N-(Trifluoroacetyl)prolyl derivatives were prepared and analyzed using GC/MS. In one case, pure d-isomers of methamphetamine and amphetamine were detected. In the remainder of the samples involving both drugs, skewed racemates were detected, with the l-isomer of methamphetamine and the d-isomer of amphetamine predominating slightly over their enantiomers. In samples involving amphetamine only, 50:50 mixtures of d- and l-isomers were detected. In no instance was pure i-methamphetamine (from a Vicks inhaler) detected.

Pharmacokinetic consequences of spaceflight

Spaceflight induces a wide range of physiological and biochemical changes, including disruption of gastrointestinal (GI) function, fluid and electrolyte balance, circulatory dynamics, and organ blood flow, as well as hormonal and metabolic perturbations. Any of these changes can influence the pharmacokinetics and pharmacodynamics of in-flight medication. That spaceflight may alter bioavailability was proposed when drugs prescribed to alleviate space motion sickness (SMS) had little therapeutic effect. Characterization of the pharmacokinetic and/or pharmacodynamic behavior of operationally critical medications is crucial for their effective use in flight; as a first step, we sought to determine whether drugs administered in space actually reach the site of action at concentrations sufficient to elicit the therapeutic response.

Homogeneous, micelle quenching fluoroimmunoassay for detecting amphetamines in urine

We developed a homogeneous fluoroimmunoassay for detecting amphetamines in urine. Only fluorescence intensity need be measured because the emission of non-protein-bound fluorescein-labeled amphetamine is preferentially quenched by detergent micelles. In a previous reported prototype assay system for measuring gentamicin in serum we used fluorescein and dodecyl sulfate (Anal Chem 1985; 57:1928-30). We have found that favorable hydrophobic and (or) ionic character of the analyte and unfavorable polar and (or) ionic character of the fluor are important determinants of the desired interactions. An anionic detergent and fluorescein, therefore, should be appropriate for apolar of cationic analytes, such as gentamicin and amphetamines. A greater [H+] at the anionic micelle surface is important for quenching emission from the fluor moiety. Millimolar concentrations of dodecyl sulfate rapidly denature immunoglobulin unless hapten is bound with sufficiently high affinity. Affinity was sufficiently high for the antibody used in the prototype gentamicin assay but not for the amphetamine antibody. Thus for the amphetamine assay, we used a non-denaturing detergent, dodecyl(oxyethylene)12 sulfate. The assay requires 30 microL of specimen in 2 mL of total assay volume. Amphetamine(d-,dl-, and meth-), at a concentration of 1 mg per liter of urine, is readily detected.

Urinary phenethylamine response to d-amphetamine in 12 boys with attention deficit disorder

Urinary phenethylamine (PEA), an endogenous amine similar to amphetamine in both molecular structure and pharmacological properties, was studied in 12 boys with attention deficit disorder with hyperactivity. d-Amphetamine and placebo were given for 14 days each in a counterbalanced crossover design; double-blind teacher behavior ratings and motor activity measurements were also obtained. Excretion of PEA, phenylacetic acid, creatinine, and d-amphetamine were measured. PEA was significantly increased and phenylacetic acid was unchanged after d-amphetamine administration, and change in PEA excretion correlated significantly with d-amphetamine excretion. There was no significant relationship between either clinical response to drug and change in PEA or phenylacetic acid excretion.

Drug abuse proficiency testing

Concerning drugs in general, proficiency testing has undoubtedly been a major contributing factor to improved detection. Some of the improvement may be due to advances in technology, and this is possibly the case with improvement in the detection of morphine and methadone. The improvement in the determination of methamphetamine within three surveys over six months can clearly be attributed to proficiency testing. In drug screening for cocaine abuse, the poor results in proficiency testing for the detection of the primary metabolite, benzoylecgonine, has clearly demonstrated that laboratories are not proficient in this screening.

Subjective responses and excretion patterns of dextroamphetamine after the administration of therapeutic doses

Twelve male medical and graduate students received dextroamphetamine sulfate in doses of 0, 5, 10, and 15 mg/70 kg body weight. The study was conducted in a double-blind manner, and treatments were assigned according to randomized, complete block design. The drug was given orally and subjects were instructed not to eat 3 1/2 h prior to administration. After administration, total urine output was collected for 12 h; no attempt was made to control urinary pH to more realistically approach the general clinical usage of amphetamines. The urine was pooled into two 6-h segments and analyzed for amphetamine concentration. Subjective impressions of the treatments were also evaluated by means of the Cornell Medical Index Questionnaire. Results showed that approximately 30% of the total dose was excreted unchanged within 12 h after administration. The amount excreted agreed very closely with the doses given and paralleled the scores for subjective impressions by the subjects. None of the subjects felt that their driving would be impaired for any of the doses administered. This study indicates that under ordinary conditions (in which pH is not artificially controlled), therapeutic doses of dextroamphetamine can be detected in urine for up to 12 h after oral administration.

Amphetamine poisoning in dogs

Amphetamine intoxication in dogs referred to the Veterinary Diagnostic Laboratory or the Veterinary Hospital of the University of Minnesota was characterized by excitement, agitation, hyperthermia, and convulsive episodes that could be confused with other convulsant poisonings. Extraction procedures on stomach contents or urine enabled indentification of the drug, using ultraviolet spectrophotometry.

Effect of ethanol on toxicity and metabolism of amphetamine in the mouse

Ethanol, 3 g/kg i.p., did not significantly alter the acute toxicity of amphetamine in the mouse. However, the urinary metabolite pattern was changed, suggesting that ethanol suppressed metabolism of the stimulant during the initial 6 h period. After 24 h, the mouse metabolized the same fraction of a given dose of amphetamine, whether it was given as amphetamine alone or amphetamine mixed with 2,3 or 4 g/kg ethanol.

Levo(-) amphetamine and dextro(+) amphetamine in the treatment of narcolepsy

The narcoleptic syndrome is a life-long and sometimes familial disorder in which there is a disturbance of the rapid eye movement phase of sleep. Patients with periodic sleep in the daytime but no other symptoms seldom develop the narcoleptic syndrome and have a separate unrelated disorder. Twelve patients with the narcoleptic syndrome were treated separately with l(-) amphetamine and d(+) amphetamine. Both drugs abolished narcolepsy, d(+) amphetamine being slightly more potent than l(-) amphetamine. In equipotent doses, unwanted effects of nervousness and insomnia were equal in frequency. No tolerance to either preparation developed during a six month period. Cataplexy was not affected by amphetamine treatment, but was abolished in two patients when clomipramine was given together with either amphetamine.

A note on the influence of diet in West Africa on urinary pH and excretion of amphetamine in man

The urinary excretion of amphetamine was examined after the oral administration of (+)-amphetamine sulphate to two groups of subjects whose urinary pH fluctuated about mean acidic or alkaline values due to their different diets. The group with a balanced protein diet giving acidic urine, excreted much more drug unchanged than the group with a low protein diet giving alkaline urine. A small increase in protein intake in the group with alkaline urine made their urine pH acidic in a few days and increased their excretion of amphetamine to the same level as the group with acid urine.