Interindividual and Intraindividual Variation of Methylphenidate Concentrations in Serum and Saliva of Patients With Attention-Deficit/Hyperactivity Disorder.

BACKGROUND: Therapeutic drug monitoring is becoming increasingly important in psychiatric therapy, especially in children. However, for several reasons, it cannot yet be implemented as a daily routine in clinical or outpatient settings. To evaluate new, noninvasive procedures, blood and saliva (oral fluid) samples were collected from patients with attention-deficit/hyperactivity disorder (ADHD) who were also being administered methylphenidate (MPH). The study's main purposes were to correlate MPH concentrations in serum and saliva between subjects and to analyze intraindividual variation of serum concentration. METHODS: Thirty-six patients with ADHD (27 children and 9 adults) on MPH medication were included for drug analysis. MPH and its major metabolite ritalinic acid were quantified using liquid chromatography-tandem mass spectrometry measurements. The following correlations were investigated: (1) between drug concentrations in serum and saliva, and (2) between pH value and saliva to serum concentration ratio. Furthermore, the mean intraindividual MPH-concentration fluctuation in saliva under constant frame conditions was analyzed. RESULTS: After quantification, MPH concentrations were approximately 5 times higher in the saliva than in the serum, whereas the concentrations of ritalinic acid were much lower in saliva. We found significant correlations between concentrations of MPH in serum and saliva (r = 0.51, P < 0.05). Saliva MPH measures, compared with serum, were pH-dependent (r = -0.56, P < 0.01). Daily coefficient of variance of saliva concentration in children taking constant medication was 27.3% (11%-42%), whereas the coefficient of variance for the ratio of saliva to serum was 122% (2%-2060%). CONCLUSIONS: Our data indicate that the interindividual variation in saliva to serum concentrations is rather high, whereas the intraindividual variation is fairly low, as already shown in the literature for repeated citalopram serum measurements. Saliva may well serve as an alternative matrix for therapeutic drug monitoring of MPH in patients with ADHD, especially for follow-up examinations. Future research should focus on analyzing the relationship between drug levels in saliva and clinical effects as well as on understanding the mechanisms that generate saliva drug concentrations. These are essential steps before potential clinical use.

Ethanol Interactions With Dexmethylphenidate and dl-Methylphenidate Spheroidal Oral Drug Absorption Systems in Healthy Volunteers.

BACKGROUND/PURPOSE: Ethanol coadministered with immediate-release dl-methylphenidate (dl-MPH) or dexmethylphenidate (d-MPH) significantly increases the geomean maximum plasma concentration (Cmax) of d-MPH 22% and 15%, respectively, and elevates overall drug exposure and psychostimulant effects. We asked the question: Are these ethanol-MPH interactions based more fundamentally on (1) inhibition of postabsorption d-MPH metabolism or (2) acceleration of MPH formulation gastric dissolution by ethanol in the stomach? This was investigated using the pulsatile, distinctly biphasic, spheroidal oral drug absorption systems of dl-MPH and d-MPH. METHODS: In a randomized, 4-way crossover study, 14 healthy subjects received pulsatile dl-MPH (40 mg) or d-MPH (20 mg), with or without ethanol (0.6 g/kg), dosed 4 hours later. These 4 hours allowed the delayed-release second MPH pulse to reach a more distal region of the gut to preclude gastric biopharmaceutical influences. Plasma was analyzed using a highly sensitive chiral method. Subjective/physiological effects were recorded. FINDINGS/RESULTS: Ethanol increased the second pulse of d-MPH Cmax for dl-MPH by 35% (P < 0.01) and the partial area under the plasma concentration curve from 4 to 8 hours by 25% (P < 0.05). The respective values for enantiopure d-MPH were 27% (P = 0.001) and 20% (P < 0.01). The carboxylesterase 1-mediated transesterification metabolite ethylphenidate served as a biomarker for coexposure. Ethanol significantly potentiated stimulant responses to either formulation. IMPLICATIONS/CONCLUSIONS: These findings support drug dispositional interactions between ethanol and MPH as dominant over potential biopharmaceutical considerations. Understanding the pharmacology underlying the frequent coabuse of MPH-ethanol provides rational guidance in the selection of first-line pharmacotherapy for comorbid attention-deficit/hyperactivity disorder-alcohol use disorder.

Plasma Methylphenidate Levels in Youths With Attention Deficit Hyperactivity Disorder Treated With OROS Formulation.

BACKGROUND: There are limited studies investigating the relationship between oral release osmotic system-methylphenidate (OROS-MPH) doses and plasma methylphenidate (MPH) concentrations in children and adolescents. The aim of this study was to investigate the relationship between the doses of OROS-MPH and the plasma levels of the drug. We also examined the effects of the other drugs including aripiprazole, risperidone, fluoxetine, and sertraline on the levels of the MPH in the plasma. METHODS: The files of 100 attention deficit hyperactivity disorder (ADHD) subjects (76 male, 24 female) who were diagnosed as ADHD according to the Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition criteria, were screened. The ages of subjects were between 6 and 18 years (mean = 11.5 ± 3.8 years). Plasma MPH levels were determined by high-performance liquid chromatography-tandem mass spectrometry assay. RESULTS: Daily mean OROS-MPH dose used in ADHD children was 0.7 ± 0.2 mg/kg (range: 0.3-1.3 mg/kg). The mean plasma OROS-MPH was 11.6 ± 7.3 ng/mL (range: 0.5-43.4 ng/mL). There was no group difference in the mean plasma MPH and dose-related MPH levels between the groups that used any additional drug including aripiprazole (n = 25), risperidone (n = 10), fluoxetine (n = 16), sertraline (n = 10), and did not use these drugs (P > 0.05). There was a positive correlation between the OROS-MPH doses (mg/kg) and the blood MPH levels (Pearson correlation = 0.40; P < 0.001). The plasma levels of MPH were found to be less than 13 ng/mL in 65% of the subjects. CONCLUSIONS: Our findings point to the fact that plasma levels of MPH show a wide range of changes at similar doses, correlate positively with the doses and, as expected, are not affected by using risperidone, sertraline, fluoxetine, and aripiprazole. Therapeutic drug monitoring may help to optimize MPH dose in patients not responding to treatment or in those experiencing serious side effects, but not in routine clinical practice. The presence of intermediate dose formulations such as 45-mg tablets for OROS-MPH may contribute to the optimization.

Predominance of D2 receptors in mediating dopamine's effects in brain metabolism: effects of alcoholism.

Dopamine signals through D1-like and D2-like receptors, which can stimulate or inhibit, respectively, neuronal activity. Here we assessed the balance between D1 or D2 receptor signaling in the human brain and how it is affected in alcoholism. Using PET, we measured the relationship between changes in dopamine and brain glucose metabolism induced by methylphenidate in controls and alcoholics. We show that methylphenidate induced significant DA increases in striatum, amygdala, and medial orbitofrontal cortex, whereas it decreased metabolism in these brain regions. Methylphenidate-induced dopamine increases were greater in controls than in alcoholics, whereas methylphenidate-induced metabolic decreases were greater in alcoholics. For both groups, methylphenidate-induced dopamine increases were associated with decreases in regional brain metabolism, and the correlations were strongest in subthalamic nuclei, anterior cingulate, and medial orbitofrontal cortex. These correlations were more extensive and robust and the slopes steeper in alcoholics than in controls despite their attenuated dopamine responses to methylphenidate, which suggests an impaired modulation of dopamine signals in the brain of alcoholic subjects. These findings are consistent with a predominant inhibitory effect of dopamine in the human brain that is likely mediated by the prominence of dopamine D2/D3 receptors.

Pharmacokinetic and pharmacodynamic effects of methylphenidate and MDMA administered alone or in combination.

Methylphenidate and 3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy') are widely misused psychoactive drugs. Methylphenidate increases brain dopamine and norepinephrine levels by blocking the presynaptic reuptake transporters. MDMA releases serotonin, dopamine and norepinephrine through the same transporters. Pharmacodynamic interactions of methylphenidate and MDMA are likely. This study compared the pharmacodynamic and pharmacokinetic effects of methylphenidate and MDMA administered alone or in combination in healthy subjects using a double-blind, placebo-controlled, crossover design. Methylphenidate did not enhance the psychotropic effects of MDMA, although it produced psychostimulant effects on its own. The haemodynamic and adverse effects of co-administration of methylphenidate and MDMA were significantly higher compared with MDMA or methylphenidate alone. Methylphenidate did not change the pharmacokinetics of MDMA and vice versa. Methylphenidate and MDMA shared some subjective amphetamine-type effects; however, 125 mg of MDMA increased positive mood more than 60 mg of methylphenidate, and methylphenidate enhanced activity and concentration more than MDMA. Methylphenidate and MDMA differentially altered facial emotion recognition. Methylphenidate enhanced the recognition of sad and fearful faces, whereas MDMA reduced the recognition of negative emotions. Additionally, the present study found acute pharmacodynamic tolerance to MDMA but not methylphenidate. In conclusion, the combined use of methylphenidate and MDMA does not produce more psychoactive effects compared with either drug alone, but potentially enhances cardiovascular and adverse effects. The findings may be of clinical importance for assessing the risks of combined psychostimulant misuse. Trial registration identification number: NCT01465685 (http://clinicaltrials.gov/ct2/show/NCT01465685).

Methylphenidate intoxication: somnolence as an uncommon clinical symptom and proof of overdosing by increased serum levels of ritalinic acid.

There is considerable evidence for an increase of methylphenidate (MPH) abuse; thus, physicians might be confronted more frequently with MPH intoxications. Possible symptoms of intoxications with MPH are orofacial, stereotypic movements and tics as well as tachycardia, cardiac arrhythmias, arterial hypertension, hyperthermia, hallucinations and epileptic seizures. Here we report a patient who demonstrated somnolence as an uncommon clinical feature of MPH intoxication. The patient exhibited subnormal MPH serum levels (3 µg/l), however markedly increased serum levels of ritalinic acid (821 µg/l; inactive metabolite of MPH), that finally confirmed the initially suspected MPH intoxication. Due to the short half-life of orally administered MPH (t1/2~3 h) the sole measurement of MPH serum levels might be misleading concerning the proof of MPH overdosing in some cases. Parallel measurement of MPH and ritalinic acid is recommended in cases with suspected MPH intoxication and insufficient anamnestic data.

[LC-MS/MS assay of methylphenidate: stability and pharmacokinetics in human].

The study aims to solve the instability problem of methylphenidate (MPH) in plasma, and establish a LC-MS/MS method for simultaneous determining of MPH in human plasma. The stabilities of MPH in different media were studied, and the degradation characteristics of MPH in these media were also investigated by HPLC and LC-MS/MS. To a 200 microL aliquot of freshly collected plasma sample, 10 microL 2% formic acid was added immediately to prevent the hydrolysis of MPH in human plasma samples. Chromatographic separation was performed on a Sapphire C18 column using the mobile phase of methanol - 5 mmol.L-1 ammonium acetate buffer solution containing 0.1% formic acid (46 : 54). MPH was quantified by tandem mass spectrometry operating in positive electrospray ionization mode with multiple reaction monitoring. The detection used the transitions of protonated molecules at m/z 234.2-->84.1 for MPH and m/z 260.3-->183.1 for propranolol (IS), separately. The intra- and inter-assay precisions were all below 5.0%. The accuracies were all in standard ranges. The linear calibration curve was obtained in the concentration range of 0.035-40 ng.mL-1. The methods fulfilled the demand. The method was used to determine the concentration of MPH in human plasma after a single dose of 36 mg MPH tablet to 6 healthy Chinese volunteers. The method is suitable for the precisely determination of MPH and for pharmacokinetic study of MPH in human plasma.

Methylphenidate-elicited dopamine increases in ventral striatum are associated with long-term symptom improvement in adults with attention deficit hyperactivity disorder.

Stimulant medications, such as methylphenidate, which are effective treatments for attention deficit hyperactivity disorder (ADHD), enhance brain dopamine signaling. However, the relationship between regional brain dopamine enhancement and treatment response has not been evaluated. Here, we assessed whether the dopamine increases elicited by methylphenidate are associated with long-term clinical response. We used a prospective design to study 20 treatment-naive adults with ADHD who were evaluated before treatment initiation and after 12 months of clinical treatment with a titrated regimen of oral methylphenidate. Methylphenidate-induced dopamine changes were evaluated with positron emission tomography and [(11)C]raclopride (D(2)/D(3) receptor radioligand sensitive to competition with endogenous dopamine). Clinical responses were assessed using the Conners' Adult ADHD Rating Scale and revealed a significant reduction in symptoms of inattention and hyperactivity with long-term methylphenidate treatment. A challenge dose of 0.5 mg/kg intravenous methylphenidate significantly increased dopamine in striatum (assessed as decreases in D(2)/D(3) receptor availability). In the ventral striatum, these dopamine increases were associated with the reductions in ratings of symptoms of inattention with clinical treatment. Statistical parametric mapping additionally showed dopamine increases in prefrontal and temporal cortices with intravenous methylphenidate that were also associated with decreases in symptoms of inattention. Our findings indicate that dopamine enhancement in ventral striatum (the brain region involved with reward and motivation) was associated with therapeutic response to methylphenidate, further corroborating the relevance of the dopamine reward/motivation circuitry in ADHD. It also provides preliminary evidence that methylphenidate-elicited dopamine increases in prefrontal and temporal cortices may also contribute to the clinical response.

Use of partial AUC (PAUC) to evaluate bioequivalence--a case study with complex absorption: methylphenidate.

PURPOSE: Methylphenidate modified-release products produce early and late peak concentrations critical for treatment of morning and afternoon symptoms of attention deficit hyperactivity disorder (ADHD). Standard bioequivalence (BE) criteria cannot be applied to these products. The performance of partial area under the drug concentration-time curve (PAUC), Cmax and AUCINF to assess BE were independently evaluated for two products. METHODS: A two-stage analysis was performed on plasma data for two methylphenidate modified-release products (Product 1 and 2). Simulations using the fitted parameters determined how changes in fast absorption rate constant (K0Fast) and fraction available (F1) affected curve shape and BE determination using Cmax, AUCINF and PAUC. RESULTS: The sensitivity of the mean PAUC(test)/PAUC(reference) ratios to changes in K0Fast(test) are product dependent. Product 1 mean PAUC(test)/PAUC(reference) ratios for PAUC0-4h are more responsive to both decreases and increases in K0Fast(test) than Product 2. Product 2 showed a greater response in the mean PAUC(test)/PAUC(reference) ratio for PAUC0-4h when the K0Fast(test) is decreased and less response as the value is increased. CONCLUSIONS: PAUC estimated curve shape is sensitive to changes in absorption and are product specific, and may require a new PAUC metric for each drug. A non-product specific metric to assess curve shape is warranted.

Long-term safety of OROS methylphenidate in adults with attention-deficit/hyperactivity disorder: an open-label, dose-titration, 1-year study.

OBJECTIVE: To evaluate the long-term safety of OROS methylphenidate in the management of attention-deficit/hyperactivity disorder (ADHD) in adults. METHODS: This multicenter, open-label, dose-titration, flexible dose study enrolled adults with ADHD for 6 or 12 months of treatment with OROS methylphenidate. Dosing began at 36 mg/d, with titration in 18-mg increments every 7 days until a predefined outcome (efficacy threshold, maximum dosage of 108 mg/d, or limiting adverse event). Dose reduction occurred for prespecified reasons, and the subjects discontinued if unable to tolerate 36 mg/d. Assessments included ADHD symptoms, adverse events, vital signs, and laboratory results. RESULTS: A total of 550 subjects received treatment (52% were men; mean age, 39 years; range, 18-65 years), and 57% (146/258) and 44% (129/292) completed their 6 or 12 months of treatment with mean durations of 128 and 213 days, respectively. The final prescribed dosages were 36 mg/d (22.4%), 54 mg/d (25.1%), 72 mg/d (22.0%), 90 mg/d (17.1%), and 108 mg/d (13.5%). Modest increases from baseline to final visit were observed in mean systolic (2.6 mm Hg) and diastolic (1.9 mm Hg) blood pressure and pulse (4.1 beats per minute). The mean weight decreased by 2.3 kg. No clinically meaningful changes in laboratory values or electrocardiogram parameters were observed other than increased heart rate. Most common adverse events included decreased appetite (26.7%), headache (24.0%), and insomnia (20.7%). No serious adverse event was considered related to study medication. Several measures of efficacy indicated improvement during the study. CONCLUSIONS: OROS methylphenidate, in the flexible dosage range from 36 to 108 mg/d, was well tolerated for up to 1 year in adults with ADHD.

Quantitative determination of methylphenidate in plasma by gas chromatography negative ion chemical ionisation mass spectrometry using o-(pentafluorobenzyloxycarbonyl)-benzoyl derivatives.

The use of a novel electrophoric derivatisation reagent, o-(pentafluorobenzyloxycarbonyl)-benzoyl chloride, for the quantitative determination of methylphenidate in plasma is described. The drug can be quantitatively measured down to 72 pg/mL plasma using only 250 µL of sample due to the extraordinary sensitivity of the derivatives under negative ion chemical ionisation mass spectrometry. Plasma samples were made alkaline with carbonate buffer and treated with extraction solvent n-hexane and reagent solution for 30 min, which, after concentration, was measured by GC-NICI-MS. The method is rapid as extraction and derivatisation occur in one single step. A stable isotope-labelled internal standard was used and its synthesis described. Full validation data are given to demonstrate the usefulness of the assay, including specificity, linearity, accuracy and precision, long-term stability, short-term stability, freeze-thaw stability, stock solution stability, autosampler stability, aliquot analysis, robustness, matrix effect, and prospective analytical batch size accuracy. The method has been successfully applied to pharmacokinetic profiling of the drug after oral application.

HPLC determination of methylphenidate and its metabolite, ritalinic acid, by high-performance liquid chromatography with peroxyoxalate chemiluminescence detection.

An HPLC-peroxyoxalate chemiluminescence (PO-CL) method for simultaneous determination of methylphenidate (MPH) and ritalinic acid (RA) was developed. The method was used to monitor MPH and RA after administration of MPH to rats. Deproteinized plasma spiked with 1-(3-trifluoromethylphenyl)piperazine (IS) was dried and labeled with 4-(N,N-dimethylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (DBD-F). The labeled sample was cleaned with two kinds of solid-phase extraction cartridge, and the DBD-labels were separated on an ODS column with gradient elution using a mixture of CH(3)CN and imidazole-HNO(3) buffer. Separation of MPH and RA can be achieved within 33 min. The LODs of MPH and RA at a signal-to-noise ratio of 3 were 2.2 and 0.4 ng mL(-1), respectively. Moreover, monitoring of MPH and RA after MPH administration (10 mg kg(-1)) to rat could be performed. The concentration of RA 480 min after administration was eight times higher than that of MPH. The proposed HPLC-PO-CL method was useful for determination of MPH and RA in rat plasma and was successfully used to monitor these substances after MPH administration.

Correlation between methylphenidate and ritalinic acid concentrations in oral fluid and plasma.

BACKGROUND: We studied the excretion profile of methylphenidate (MPH) and its metabolite ritalinic acid (RA) in oral fluid and plasma, the oral fluid-to-plasma (OF/P) drug ratio, and the variations of oral fluid pH after drug administration. METHODS: We analyzed oral fluid and plasma samples, obtained from 8 healthy volunteers after ingestion of a single dose of 20 mg fast-release or extended-release MPH, for MPH and RA by LC-MS. We estimated the apparent pharmacokinetic parameters of MPH in plasma and oral fluid and calculated the OF/P ratio for each time interval. RESULTS: MPH and RA were detected in oral fluid. Whereas parent drug concentrations in oral fluid were an order of magnitude higher than those in plasma, the opposite was observed for RA. Oral fluid concentrations of MPH ranged between 0.5 and 466.7 microg/L and peaked at 0.5 h after administration of the fast-release formulation; they ranged between 0.7 and 89.5 microg/L and peaked at 2 h after administration of the extended-release formulation. Both formulations presented bimodal time-course curves for the OF/P ratio, ranging between 1.8 and 242.1 for the fast-release formulation and between 2.6 and 27.0 for extended-release. Oral fluid pH did not appear to be modified by the administration of the drug, and its influence on OF/P ratio did not affect the correlation of MPH between the 2 body fluids. CONCLUSIONS: The results obtained support the measurement of MPH in oral fluid as an alternative to plasma if the extended-release formulation is used.

Single- and multiple-dose pharmacokinetics of methylphenidate administered as methylphenidate transdermal system or osmotic-release oral system methylphenidate to children and adolescents with attention deficit hyperactivity disorder.

This was a 1-month, multicenter, open-label, randomized study to determine single- and multiple-dose pharmacokinetics of d,l-methylphenidate (MPH) after MPH transdermal system (MTS) and osmotic-release oral system MPH (OROS MPH) dosing in children (6-12 years) and adolescents (13-17 years) who had a diagnosis of attention deficit hyperactivity disorder. The pharmacokinetic population consisted of 33 children and 31 adolescents. Accumulation of d-MPH was 34% in children and 57% in adolescents after multiple fixed doses of MTS for 7 days and 76% and 94%, respectively, after 28 days of dosing. After 7 days of OROS MPH dosing, accumulation was 16% in children and 19% in adolescents; fixed doses of OROS MPH were not studied beyond 7 days. After escalating the doses to 30 mg per 9 hours for MTS, accumulation was 73% in children and 83% in adolescents after allowing for dose escalation. Corresponding values for OROS MPH after dose escalation to 54 mg were 33% in both age groups. Plasma l-MPH concentrations were approximately half those of d-MPH for MTS and negligible for OROS MPH. Overall, MTS accumulation was above that expected for single-dose pharmacokinetics of MTS and OROS MPH in both age groups. As a result of accumulation, systemic exposure to d-MPH in children after multiple escalating doses was 1.4- to 1.6-fold higher for MTS compared with OROS MPH, but similar in adolescents for both formulations. After all dosing, systemic exposure was greater in children compared with adolescents, consistent with lower body weight in children. Adverse events were mild to moderate for both formulations, and MTS dermal responses were mild.

Modulation of motorcortical excitability by methylphenidate in adult voluntary test persons performing a go/nogo task.

This study investigated the interaction between motorcortical excitability (short interval cortical inhibition, intracortical facilitation and long interval cortical inhibition), different requirement conditions [choice reaction test (CRT), attention/go/nogo], and their pharmacological modulation by methylphenidate (MPH) in normal healthy adults (n = 31) using a transcranial magnetic stimulation paradigm. MPH was administered in a dosage of 1 mg/kg body weight, maximum 60 mg. Additionally, serum level and clearance of MPH were controlled. The statistical analysis of variance revealed a significant three-way interaction of 2 (MPH) x 3 (CRT) x 6 (ISI) predicting motor evoked potential amplitudes (P = 0.032, MPH none and full dose, n = 31). In order to compare effects of dosage an additional between-subjects factor (half vs. full MPH dose) was introduced. None of the interactions involving this between-subject factor reached statistical significance. Exploring interactions with MPH only, a 3 (MPH none, half and full dose) x 3 (CRT) x 6 (ISI) analysis of variance revealed significant two-way interactions for MPH x ISI (P = 0.040) and condition x ISI (P < 0.001, n = 18). Effects observed for MPH were strongest on facilitatory processes, weaker for intracortical inhibition. In sum, MPH seems to interact via striato-thalamo-cortical pathways with original motorcortical processes (ISI), to a lesser extent with task-dependent or behavioral parameters (CRT).

o-(Pentafluorobenzyloxycarbonyl)benzoyl chloride: a novel electrophoric derivatisation reagent for amino compounds designed for negative ion chemical ionisation mass spectrometry.

The synthesis of a novel electrophoric derivatisation reagent, o-(pentafluorobenzyloxycarbonyl)benzoyl chloride, is described. The reagent was tested against selected primary and secondary amino compounds as analytical targets. The derivatives exhibit excellent mass spectral properties under negative ion chemical ionisation (NICI), i.e. reduced fragmentation and thus high ion current for the targeted m/z during analysis. Since the reagent bears a pentafluorobenzyl ester group, resulting mass NICI mass spectra were expectedly dominated by dissociative resonance electron capture typically observed with these compounds. The reagent is suitable for detecting volatile primary and secondary amines with high sensitivity. Background is reduced by a shift in detected m/z and retention time, as demonstrated for the analysis of the drug methylphenidate from human plasma.

HPLC enantioseparation of α,α-diphenyl-2-pyrrolidinemethanol and methylphenidate using a chiral fluorescent derivatization reagent and its application to the analysis of rat plasma.

Enantioseparation of α,α-diphenyl-2-pyrrolidinemethanol (D2PM) and methylphenidate (MPH; Ritalin(®)) using (R)-(-)-4-(N,N-dimethylaminosulfonyl)-7-(3-isothiocyanatopyrrolidin-1-yl)-2,1,3-benzoxadiazole as the chiral derivatization reagent has been achieved for the first time, and a simple, reliable detection method using HPLC with fluorescence detection has been developed. D2PM and MPH have been derivatized with (R)-(-)-4-(N,N-dimethylaminosulfonyl)-7-(3-isothiocyanatopyrrolidin-1-yl)-2,1,3-benzoxadiazole at 55°C for 15 min. The derivatives of D2PM and MPH have been separated, completely and rapidly, using a reversed-phase system within 16 min (resolution factor (R(s))=1.60 and 2.53, respectively). The detection limits of (R)- and (S)-D2PM were found to be 6.8 and 13 ng/mL, respectively, and those of D- and L-threo-MPH were 61 and 66 ng/mL, respectively (S/N=3). The proposed method was successfully applied to the analysis of rat plasma, where the rats were separately dosed with D2PM and MPH (Ritalin).

A Pharmacokinetic Study of Methylphenidate Hydrochloride Multilayer Extended-Release Capsules (Aptensio XR®) in Preschool-Aged Children with Attention-Deficit/Hyperactivity Disorder.

OBJECTIVE: This was a single-dose, one-period, multicenter, pharmacokinetic (PK) study to evaluate the PK of methylphenidate (MPH) hydrochloride multilayer extended-release capsules (MPH-MLR) in preschool children aged 4 to < 6 years, previously diagnosed with attention-deficit/hyperactivity disorder (ADHD), and on a stable dose of MPH. METHODS: Preschool-aged children (N = 10) received a single oral dose of MPH-MLR (10, 15, or 20 mg) sprinkled over applesauce; a dose equivalent to their pre-enrollment daily dose of MPH. Blood samples for the measurement of MPH concentrations were obtained pre-dose and at 0.5, 1, 2, 3, 4, 6, 8, 10, 12, and 24 h post-dose. No structural model was assumed in the derivation of PK values for analysis. Maximum plasma concentration (Cmax), area under the concentration-time curve (AUC), elimination half-life, clearance (CL), and volume of distribution (Vd) data were compared with a historical group of older children aged 6-11 years (N = 11) and analyzed by bodyweight. Safety (adverse event monitoring, vital signs, electrocardiogram, clinical laboratory testing, physical examination) was assessed. RESULTS: Mean dose-normalized Cmax and area under the curve to the last measurable observation (AUC0-t) values were similar across dose groups, ranging from 0.67 ng/mL/mg (MPH 15 mg) to 0.81 ng/mL/mg (MPH 10 mg) for Cmax/dose, and from 7.80 h × ng/mL/mg (MPH 20 mg) to 8.92 h × ng/mL/mg (MPH 10 mg) for AUC0-t/dose. PK results were integrated into a previously described pharmacostatistical population PK model. Visual predictive check plots showed greater variability in the 6- to 11-year-old group than the 4- to < 6-year-old group, and CL increased with increasing body weight in a greater than dose-proportional manner. Mean CL, normalized for body weight, was constant for all dose groups, ranging from 4.88 L/h/kg to 5.80 L/h/kg. Median time to Cmax ranged from 2.00 to 3.00 h post-dose, and overall, dose-normalized Cmax concentrations indicated greater systemic exposures of MPH-MLR in preschool children aged 4 to < 6 years compared with children aged 6-11 years. Children aged 4 to < 6 years had a lower Vd than children aged 6-11 years. There were no unexpected safety signals. CONCLUSION: The PK of MPH-MLR in preschool children demonstrated the biphasic absorption profile described earlier in older children, and the PK profile in children with ADHD aged 4 to < 6 years was similar to the profile in those aged 6-11 years, apart from a lower Vd and relatively higher systemic MPH levels for children in the preschool group. TRIAL REGISTRATION: Clinicaltrials.gov Identifier: NCT02470234.

Dopaminergic modulation of brain systems subserving decision making under uncertainty: a study with fMRI and methylphenidate challenge.

There is evidence that the dopaminergic system is involved in probabilistic reinforcement learning and reward-related decision-making. However, little is known about the effects of external dopaminergic challenges on processing of uncertainty in decision-making tasks. Therefore, the present study examined changes in fMRI activation patterns in a natural sampling paradigm. Decision making under uncertainty was examined before and after administration of a single dose of 40 mg methylphenidate as an acute dopaminergic pharmacological challenge. We found that the level of uncertainty was positively correlated with activations in the prefrontal cortex. Conversely, negative correlations with uncertainty were found in the left hippocampus, right amygdale, and right middle temporal gyrus. The drug intervention with methylphenidate revealed a differential picture. Uncertain information processing was associated with higher activation in the parietal association cortex and posterior cingulate cortex after placebo relative to methylphenidate. The methylphenidate challenge relative to placebo was associated with higher left and right parahippocampal as well as cerebellar activation under uncertainty. Apparently, the pro-dopaminergic pharmacological influence induces a relative shift towards recruitment of hippocampal areas under uncertainty, whereas under placebo conditions, higher levels of parietal cortex activations are involved in the task. The findings suggest a role of dopamine in uncertainty processing and shed light on the pharmacological mechanisms of methylphenidate.

Liquid chromatography-electrospray ionization mass spectrometry determination of methylphenidate and ritalinic acid in conventional and non-conventional biological matrices.

A procedure based on liquid chromatography-electrospray ionization mass spectrometry is described for determination of methylphenidate (MPH) and its principal metabolite ritalinic acid (RA) in plasma, urine, oral fluid and sweat using 3,4-methylendioxypropylamphetamine (MDPA) as internal standard. Aliquots of 100microL biological fluids and sweat patch were initially treated with acetonitrile, centrifuged, and clear supernatants evaporated and redissolved in 10mM ammonium acetate. Chromatography was performed on a reversed-phase column using a gradient of 10mM ammonium acetate and acetonitrile as a mobile phase at a flow rate of 1mL/min. Separated analytes were confirmed and quantified by positive electrospray ionization mass spectrometry and selected ion monitoring acquisition mode. Limits of quantifications were 1ng/mL plasma, 1ng/sweat patch, 0.5ng/mL oral fluid and urine for MHF; 1ng/mL plasma and oral fluid, 1ng/sweat patch, 0.5ng/mL urine for RA using 100microL biological fluids or one sweat-patch per assay. Calibration curves were linear over the calibration ranges for both MPH and RA, with r(2)>0.99. At three concentrations spanning the linear dynamic range of the assay, mean recoveries ranged between 67.9-90.3% for MPH and 36.3-92.4% for RA in the different biological matrices. This method was applied to therapeutic monitoring of MHP and RA in conventional and non-conventional biological matrices from individuals in drug treatment.