Class of 2005 Abstract / Objective: The goal of this study was to determine the presence of erythro-methylphenidate (erythro-MPH) isomers contained within methylphenidate HCl (Metadate CD®) capsules. Methods: This experiment was conducted at a pharmaceutical manufacturing facility located in Tucson, Arizona. Methylphenidate HCl (MPH) capsules by Celltech Pharmaceuticals, Inc. were analyzed and compared to a reference standard. Thin-layer chromatography (TLC) was the technique used to qualitate the samples. The main outcome measure was the Rf values which were used to determine whether or not the MPH capsules contained erythro-MPH. Results: The study included ten, 20 mg MPH capsules and a reference standard (50 mg strength USP MPH related compound). The Rf value of the reference standard was 0.073 while the Rf value of the MPH samples ranged from 0.42 - 0.85. Conclusion: In this qualitative analysis of MPH capsules, there was no erythro-MPH isomers present in the MPH capsules.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 126-161).

No description available.

Spontaneously active frontal cortex and spinal cord networks grown on microelectrode arrays were used to study effects of D-methylphenidate. These central nervous system tissues have relatively low concentrations of dopaminergic and noradrenergic neurons compared to the richly populated loci, yet exhibit similar neurophysiological responses to methylphenidate. The spontaneous spike activity of both tissues was inhibited in a concentration-dependent manner by serial additions of 1-500 µM methylphenidate. Methylphenidate is non-toxic as spike inhibition was recovered following washes. The average concentrations for 50% spike rate inhibition (IC50 ± SD) were 118 ± 52 (n= 6) and 57 ± 43 (n = 11) for frontal cortex and spinal cord networks, respectively. A 3 hour exposure of a network to 1 mM methylphenidate was nontoxic. The effective concentrations described in this study are within the therapeutic dosage range. Therefore, the platform may be used for further investigations of drug mechanisms.

Thirty-one rats were trained on a differential reinforcement of low rate schedule. After responding had stabilized, animals were injected with methylphenidate, twice weekly, presession. Methylphenidate produced dose-dependent increases in response rates and decreases in reinforcements. Repetition of these doses produced a reduced drug effect, and a third administration of the 10 mg/kg dose further reduced the drug effect. Subsequently, the effects of daily and intermittent administration were determined for this dose. Daily methylphenidate, pre-session, produced tolerance to the behavioral effects of methylphenidate and cross-tolerance to the amphetamines. Twice-weekly methylphenidate, pre-session, produced partial tolerance to methylphenidate and partial cross-tolerance to the amphetamines. Thus, periodic exposure to the behaviorally disruptive effects of a drug of the amphetamine class reduces the effects of subsequent exposure.

This study analyzed methylphenidate (5 mg/kg; trade name: Ritalin) conditioned place preference (CPP) in adolescent male and female rats. Results showed MPH-induced CPP in males, but not in females. These results suggest rewarding properties of MPH may be more prominent in males as compared to females in adolescence.

Methylphenidate (MPH) is a psychostimulant drug that is commonly prescribed for Attention Deficit-Hyperactivity Disorder (ADHD), however, this drug is also abused. The primary pharmacological action of MPH is similar to that of cocaine, in that the drug blocks the dopamine transporter and enhances dopamine neurotransmission. The similarity to cocaine has brought to light legitimate concerns at the abuse liability of MPH. The focus of the present study was to analyze MPH conditioned place preference (CPP) in adolescent rats, with the focus on sex differences in this effect. CPP is a commonly used measure of drug reward in rats. Animals were also tested at two different time periods, from postnatal day (P)32-38 or P43-49, representing periods during adolescence both before and after the commencement of the estrous cycle in females, which begins on approximately P41. After an initial preference test on P32 or 43 revealed no significant preference for either context, an unbiased procedure was used. Beginning on P33 or P44, MPH (5 mg/kg) was paired with either context in animals in the drug condition, balanced across males and females. Controls were given saline in both contexts (N=8-9 in all groups). A preference test was given on P38 or P49 with dividers removed. Results revealed no sex or age difference, but MPH induced a robust increased preference for the paired context in both males and females on the post-conditioning preference test, which was significantly greater than male and female controls. Interestingly, males demonstrated significantly higher levels of activity and a higher number of entries made into the paired context when tested at the younger age, but there were no sex differences in these responses in older animals. Brain tissue is currently being analyzed for levels of the dopamine transporter (DAT), and this data will be presented. Past studies have shown that females have a higher number of DAT in the striatum compared to males in adulthood, but this has never been established in adolescence. In conclusion, it appears that a 5 mg/kg dose of MPH is capable of inducing drug reward in adolescent rats, and unlike recent results from our laboratory regarding behavioral sensitization, there are no sex differences in this response.

Thesis--PlanB (M.S.)--University of Wisconsin--Stout, 1999. / Includes bibliographical references.

abstract: The failure to withhold inappropriate behavior is a central component of most impulse control disorders, including Attention Deficit Hyperactivity Disorder (ADHD). The present study examined the effects of housing environment and methylphenidate (a drug often prescribed for ADHD) on the performance of rats in two response inhibition tasks: differential reinforcement of low rate (DRL) and fixed minimum interval (FMI). Both tasks required rats to wait a fixed amount of time (6 s) before emitting a reinforced response. The capacity to withhold the target response (volitional inhibition) and timing precision were estimated on the basis of performance in each of the tasks. Paradoxically, rats housed in a mildly enriched environment that included a conspecific displayed less volitional inhibition in both tasks compared to rats housed in an isolated environment. Enriched housing, however, increased timing precision. Acute administration of methylphenidate partially reversed the effects of enriched housing. Implications of these results in the assessment and treatment of ADHD-related impulsivity are discussed. / Dissertation/Thesis / M.A. Psychology 2011

Emerging evidence supports the use of methylphenidate (MPH) for the treatment of apathy in Alzheimer’s disease (AD). This study aimed to investigate the additional effects of MPH on attention in an AD sample and the relationship between apathy and attention. AD patients enrolled in a randomized, double-blind placebo-controlled study to examine the safety and efficacy of MPH (10mg PO twice daily) for the treatment of apathetic symptoms were tested on attention and apathy every 2 weeks for 6 weeks. A mixed effects linear regression revealed attention change scores (endpoint - baseline) over time favouring MPH (δ=1.01, p=0.03), though there were no significant associations between apathy and attention change scores (r=-0.08, p=0.54). These results suggest that while MPH can improve both apathy and attention, the effects appear independent in this patient population. This study provides insight into the different effects MPH can produce in a heterogeneous disease such as AD.