DEXAMPHETAMINE and METHYLPHENIDATE are medications used to treat Attention-deficit Hyperactivity Disorder (ADHD).
Consultant psychiatrist today i’ll be touching on methylphenidate this was a request from one of our viewers and i thought this was a really really great question so i’ll be covering the psychopharmacology of these two agents now both dexamphetamine and methylphenidate are used in adhd attention deficit hyperactivity
Disorder on adhd the evaluation of that condition now when we think about the amphetamine versus methylphenidate the main thing that both of these agents are doing to assist in adhd is this focus here on the prefrontal cortex because the prefrontal cortex is really the seat of cognition all of those things that can
Be affected in adhd organization etc so in the prefrontal cortex dopamine receptors noradrenaline and the alpha-2 presynaptic and post-synaptic receptors are the main ones that we’re looking to target in the treatment so today what i’m going to be focusing on is dopamine and noradrenaline because those are
The main neurotransmitters that these two agents increase in the extracellular space so that they those benefits to treat adhd so let’s firstly comes in many trade names um there is the immediate version ritalin there is a long acting version ritalin long acting and there’s also concerta so there are different
Formulations and the different formulations are there’s immediate release that only lasts for a short period of time you know uh onset of action is about 20 to 60 minutes and might last for maybe three four hours um about that much whilst when we look at concerto that’s pushing further lasting for much longer about
12 13 14 hours somewhere and then is basically a non-competitive inhibitor of and dopamine transporter by inhibiting it it prevents the uptake of noradrenaline into the presynaptic neuron it prevents the uptake of dopamine into the presynaptic neuron therefore there’s lots of noradrenaline and lots of dopamine
Available in this synaptic cleft to act on those receptors uh in the postsynaptic aspect to provide those benefits so that’s what methylphenidate does there’s some evidence that it also acts on the alpha-2 receptors providing that further benefit on clonidine and prazosin so you can have a are that’s sort of the
Main aspect block that blocked that increased levels of both enter amphetamine of course we’re going to talk about dexamphetamine but we know there’s methamphetamine so and there’s less dexamphetamine which we’ll be talking about as well but essentially what this agent does is it also blocks nat and that
Additional benefits that come beyond that so by blocking nat and dat there’s increase in orange adrenaline and dopamine just like methylphenidate second it is a competitive inhibitor of the vesicular monomine transporter is situated dopamine into vesicles so what amphetamine does will actually fall out of those
Vesicles so it will basically remain in this cytosolic space remember there’s already lots of dopamine here right but it’s doing extra it’s competitively inhibiting vmat and then what it’s doing function of that is to uptake dopamine this one does the reverse so what amphetamine will do it will actually act
As a reverse dat inhibitor which means it will push instead of taking it up as a data inhibitor it’s a reverse that inhibitor which means it will push dopamine out further so you can see there are these triple whammy effects not only blocking that and nats so you get non-adrenal and dopamine but then compete with vmat
Push it under the cytosolic space displace it and then further through reverse dopamine transporter inhibition you push it out further lots more dopamine into the synaptic cleft what does that tell us it tells us that this that’s why the euphoric effect is there as well because of this super extra release
Amphetamine or amphetamines are much more potent think about dexamphetamine we have the short dexamphetamine again onset very very quick and lasts maybe three to four hours but there is the longer acting version such as lisdexamphetamine uh which is known as vivants um and what that does is when you when it’s taken they it’s
Cleaved into cleaved and that’s when the absorption um is it this way so therefore it’s a long-acting is that we need optimal doses so we think about using a short acting or a long acting whatever it preferred in a sec but essentially the aim is to provide an optimal level of dopamine or adrenaline because
Too little results in symptoms of adhd too much can actually result in not only side effects but actually rigidity inflexibility of the prefrontal lobe so we need a real optimum level of these agents and generally we want to consider long-acting agents because you see short-acting agents provide sort of pulsatile dopamine
Release longer-acting so think about it this way right which mimics more substance use or using say amphetamines tonic firing of dopamine that’s nice and rhythmic because that is more adaptive hence why longer acting agents may be considered beneficial so non-competitive inhibitor you get dopamine you
Get noradrenaline with amphetamines you get these three-pronged effect that nat one two competitive v-mat inhibitor so release of dopamine into this cytosol and then reverse dopamine um inhibition uh dopamine transporter inhibition so release all of that dopamine from the cytosol into so i hope that this gives you an
Idea about it useful if you liked the video leave us a like and i hope to see you in another edition of you
Transcribed from video
Difference between DEXAMPHETAMINE & METHYLPHENIDATE in ADHD | ADDERALL | RITALIN | DR REGE EXPLAINS By Dr Sanil Rege’s Hub – Psychiatry Simplified
