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Hydrolysis of the methyl ester (±)- threo-methyl phenidate afforded the free acid in 40% yield, viz. (±)- threo-ritalinic acid, C13H17NO2. Hydrolysis and subsequent crystallization were accomplished at pH values between 5 and 7 to yield colourless prisms which were analysed by X-ray crystallography. Crystals of (±)- threo-ritalinic acid belong to the P21/ n space group and form intermolecular hydrogen bonds. An antiperiplanar disposition of the H atoms of the (HOOC-)CH-CHpy group (py is pyridine) was found in both the solid (diffraction analysis) and solution state (NMR analysis). It was also determined that (±)- threo-ritalinic acid conforms to the minimization of negative gauche+- gauche− interactions. [ABSTRACT FROM AUTHOR]

Abstract: Methylphenidate is widely used as a treatment option for attention deficit hyperactivity disorder. In animal models of attentional impairment, it is an important validation to determine whether this clinically effective treatment attenuates deficits. The purpose of the current study was to determine whether methylphenidate can diminish attentional impairment induced by three pharmacological agents with different mechanisms of action: scopolamine, mecamylamine, and dizocilpine. Female rats were trained on an operant visual signal detection task. Ten min before the test, the rats were injected subcutaneously with methylphenidate (0, 0.1, 0.3 mg/kg), scopolamine (0, 0.005, 0.01 mg/kg), mecamylamine (0, 2, 4 mg/kg), dizocilpine (0, 0.025, 0.05 mg/kg) or combinations of methylphenidate with these drugs. In each of the experiments, all rats received every treatment in a repeated measures counterbalanced order. Correction rejection accuracy was impaired by all three of the antagonists and these effects were attenuated by methylphenidate. Both scopolamine at 0.01 and dizocilpine at 0.05 mg/kg significantly impaired percent correct rejection choice accuracy, an effect that was ameliorated by methylphenidate. Mecamylamine (4 mg/kg) impaired attentional performance by reducing percent hit and percent correct rejection. Co-administration of methylphenidate failed to significantly affect the mecamylamine-induced attentional impairment. Methylphenidate alone at 0.3 mg/kg significantly improved percent hit choice accuracy only in low-performing rats in one experiment, an effect which was reversed by scopolamine. These data show that methylphenidate effectively reverses the attentional impairment caused by scopolamine and dizocilpine. These findings further validate the operant visual signal detection task for assessing attentional impairments and their reversal. [Copyright &y& Elsevier]

Abstract: The enduring effects of postweaning subchronic methylphenidate (MP) treatment and/or previous early preweaning methamphetamine (MA) application on dopamine (DA) fiber density were investigated in multiple cortical and subcortical areas of the gerbil brain. The study aimed to explore three questions: (1) is the development of DA fiber innervation in control animals sensitive to a clinically relevant subchronic treatment with MP? (2) Is the development of DA fiber innervation in the forebrain altered by a single early MA challenge? (3) If so, might the subsequent institution of a therapeutically relevant MP application scheme interfere with such early induced alternative developmental trajectories for DA fiber innervation? For this purpose, gerbils pretreated both with saline and MA (50 mg/kg, i.p.) on day 14 received either H2O or MP (5 mg/kg) orally on days 30 to 60. On day 90, DA fibers were immunohistochemically detected and quantified. As a result, MP on its own did not have any significant influence on the postnatal development of the DA fiber systems, whereas it prevented a previously MA triggered suppressive development of DA fiber innervation in the prefrontal cortex and amygdala complex (30% less fiber innervation in both areas). Thus, MP prevented previously initiated miswiring of DA fibers from actually being implemented in the gerbil forebrain. During earlier studies, rather complex miswiring has been documented in response to an early preweaning MA challenge. This miswiring was associated with functional deficits resembling some of the symptoms of patients with ADHD. Therefore, morphogenetic properties of MP need further attention. [Copyright &y& Elsevier]

Ritalin or methylphenidate (MPH) is prescribed for the treatment of attention deficit hyperactivity disorder (ADHD) and narcolepsy. The present report concerns the development and validation of an enantioselective reversed-phase liquid-chromatography/tandem mass spectrometry (LC/MS/MS) method, which was used in the determination of plasma concentrations of d- and l-antipodes of MPH in toxicokinetic (TK) studies in rats, rabbits, and dogs, following repeated daily oral dosing for up to 13 weeks. The sample processing involved the addition of sodium bicarbonate (1.0 M, pH 10) to plasma followed by liquid–liquid extraction using cyclohexane. Vancomycin, an amphoteric macrocyclic glycopeptide, produced by Streptomyces orientalis proved to be a rugged chiral selector for LC/MS/MS analysis of MPH. In all species, MPH appeared to be rapidly absorbed (Tmax=0.5–2 h). Generally, the plasma exposure (area under the plasma concentration–time curve (AUC) and Cmax)) of MPH was over-proportional to the dose. No differences in TK of MPH were observed between male and female dogs whereas in rats, females generally exhibited a slightly higher level of exposure than males. No unusual level of accumulation of MPH inconsistent with previously reported half-life (T1/2∼2.5 h) of this compound was observed. [Copyright &y& Elsevier]

Ritalin® (methylphenidate) is an amphetamine-like prescription stimulant commonly used in the treatment of attention deficit hyperactivity disorder in children and adults. Recently, the recreational use of Ritalin has increased, particularly among young adults. Well-known symptoms of intoxication include signs of sympathetic nervous stimulation, such as agitation, anxiety, tachycardia, hypertension, headache, tremor, and dizziness. This case report describes oral dyskinesia as a rare presentation of Ritalin intoxication, with the review of pathophysiology and some epidemiological data. [ABSTRACT FROM AUTHOR]