Executive function, including working memory, attention and inhibitory control, is crucial for decision making, thinking and planning. Lisdexamfetamine, the prodrug of d-amphetamine, has been approved for treating attention-deficit hyperactivity disorder and binge eating disorder, but whether it improves executive function under non-disease condition, as well as the underlying pharmacokinetic and neurochemical properties, remains unclear. Here, using trial unique non-matching to location task and five-choice serial reaction time task of rats, we found lisdexamfetamine (p.o) enhanced spatial working memory and sustained attention under various cognitive load conditions, while d-amphetamine (i.p) only improved these cognitive performances under certain high cognitive load condition. Additionally, lisdexamfetamine evoked less impulsivity than d-amphetamine, indicating lower adverse effect on inhibitory control. In vivo pharmacokinetics showed lisdexamfetamine produced a relative stable and lasting release of amphetamine base both in plasma and in brain tissue, whereas d-amphetamine injection elicited rapid increase and dramatical decrease in amphetamine base levels. Microdialysis revealed lisdexamfetamine caused lasting release of dopamine within the medial prefrontal cortex (mPFC), whereas d-amphetamine produced rapid increase followed by decline to dopamine level. Moreover, lisdexamfetamine elicited more obvious efflux of noradrenaline than that of d-amphetamine. The distinct neurochemical profiles may be partly attributed to the different action of two drugs to membranous catecholamine transporters level within mPFC, detecting by Western Blotting. Taken together, due to its certain pharmacokinetic and catecholamine releasing profiles, lisdexamfetamine produced better pharmacological action to improving executive function. Our finding provided valuable evidence on the ideal pharmacokinetic and neurochemical characteristics of amphetamine-type psychostimulants in cognition enhancement.

Taste masking is critical to improving the compliance of pediatric oral dosage forms. However, it is challenging for extremely bitter lisdexamfetamine dimesylate (LDX) with a long half-life and given in large dose. The present study aims to develop an immediate-release, taste-masked lisdexamfetamine chewable tablet. Lisdexamfetamine-resin complexes (LRCs) were prepared using the batch method. The molecular mechanism of taste masking was explored by PXRD, PLM, STA, and FT-IR. The results showed that taste masking was attributed to the ionic interaction between drug and the resin. The ion exchange process conformed to first-order kinetics. The rate-limiting step of drug release was the diffusion of ions inside the particles, and the concentration of H+ was the key factor for immediate release. The masking efficiency of the prepared LRCs in saliva exceeded 96%, and the drug could be completely released within 15 min in aqueous HCl (pH 1.2). Furthermore, the SeDeM expert system was used for the first time to comprehensively study the powder properties of LRCs and to quickly visualize their defects (compressibility, lubricity/stability, and lubricity/dosage). The selection of excipients was targeted rather than traditional screening, thus obtaining a robust chewable tablet formulation suitable for direct compression. Finally, the difference between chewable tablets containing LRCs and chewable tablets containing lisdexamfetamine dimesylate was compared by in vitro dissolution test, electronic tongue, and disintegration test. In conclusion, an immediate-released, child-friendly lisdexamfetamine chewable tablets without bitterness was successfully developed by the QbD approach, using the SeDeM system, which may help in further development of chewable tablets.

Twelve impurities (process-related and degradation) in lisdexamfetamine dimesylate (LDX), a central nervous system (CNS) stimulant drug, were first separated and quantified by high-performance liquid chromatography (HPLC) and then identified by liquid chromatography mass spectrometry (LC-MS). The structures of the twelve impurities were further confirmed and characterized by IR, HRMS and NMR analyses. Based on the characterization data, two previously unknown impurities formed during the process development and forced degradation were proposed to be (2S)-2,6-di-(lysyl)-amino-N-[(1S)-1-methyl-2-phenyl ethyl]hexanamide (Imp-H) and (2S)-2,6-diamino-N-[(1S)-1-methyl-2-(2-hydroxyphenyl)ethyl] hexanamide (Imp-M). Furthermore, these two compounds are new. Probable mechanisms for the formation of the twelve impurities were discussed based on the synthesis route of LDX. Superior separation was achieved on a YMC-Pack ODS-AQ S5 120A silica column (250 × 4.6 mm × 5 μm) using a gradient of a mixture of acetonitrile and 0.1% aqueous methanesulfonic acid solution. The HPLC method was optimized in order to separate, selectively detect, and quantify all the impurities. The full identification and characterization of these impurities should prove useful for quality control in the manufacture of lisdexamfetamine dimesylate.

Attention deficit hyperactivity disorder (ADHD) is one of the most common neurobehavioral disorders. We carried out this comparison of multiple treatments based on sufficient data in attempt to evaluate the efficacy and safety of ADHD medication for children and adolescents. PubMed, Embase and the Cochrane Database were used to search for relevant articles. Changes in the ADHD Rating Scale (ADHD-RS) scores and the Conners\' Parent Rating Scale-Revised (CPRS) scores were used as outcomes for efficacy. Withdrawals due to all-cause, adverse effects and lack of efficacy were defined as primary outcomes evaluating the safety of such medications. Both pair-wise and network meta-analyses were performed. Efficacy and safety of atomoxetine (ATX), bupropion (BUP), clonidine hydrochloride (CLON), guanfacine extended release (GXR), lisdexamfetamine dimesylate (LDX), and methylphenidate (MPH) were evaluated. LDX has the highest efficacy and a relatively lower rate of adverse effects compared to BUP, CLON and GXR. MPH has the lowest incidence rate of adverse effects and takes second place concerning ADHD-RS scores and third place concerning CPRS scores. ATX has the lowest incidence rate of all-cause withdrawals. The efficacy of ATX seems, however, to be lower than CLON, GXR, LDX and MPH. Adversely, BUP has the highest incidence rate of withdrawals and the second highest probability of causing adverse effects as well as lack of efficacy; therefore it should not be recommended as a treatment for ADHD.