Difference between DEXAMPHETAMINE & METHYLPHENIDATE in ADHD | ADDERALL | RITALIN | DR REGE EXPLAINS

hi everyone welcome to hub bytes i'm sanil rege consultant psychiatrist today I'll be touching on   the difference between dexamphetamine versus  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  so check out the video that we've done   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   attention concentration focus set shifting  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   can go and act on these receptors to provide  those benefits to treat adhd so let's firstly   cover methylphenidates now methylphenidate  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   so when we think about methylphenidates it  is basically a non-competitive inhibitor of   nat and that what that means is it will  inhibit nat nor adrenaline transporter   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   for alpha-2 receptors i've covered a video  on clonidine and prazosin so you can have a   viewing of that to go into more detail  there so that's methylphenidate those   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   there is dexamphetamine there's amphetamines  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   but what's really crucial here is these  additional benefits that come beyond that so   by blocking nat and dat there's increase in orange  adrenaline and dopamine just like methylphenidate   but it also does something else the  second it is a competitive inhibitor of   the vesicular monomine transporter you see  the vesicular monomine transporter is situated   in the presynaptic neuron basically packages  dopamine into vesicles so what amphetamine does   it will compete for that and take  up space therefore this dopamine   will actually fall out of those vesicles so it  will basically remain in this cytosolic space   then there is a third thing that happens so  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   it is a reverse it has so normally the  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   of dopamine so what it tells us is that dex  amphetamine or amphetamines are much more potent   medications or substances compared to  methylphenidate now of course when we   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   the stomach the lysine um sort of tail it's  cleaved and that's when the absorption um is   it sort of delays the absorption let's put  it this way so therefore it's a long-acting   agent right now the basic principle  with any of these agents and doses etc   is that we need optimal doses so we think about  using a short acting or a long acting whatever it   is and we'll see why long-acting agents are  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   pulsatile release what we want is more a  tonic firing of dopamine that's nice and rhythmic   because that is more adaptive hence why longer  acting agents may be considered beneficial so   in summary methylphenidate that not  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   the synaptic cleft for that euphoric effect  so i hope that this gives you an idea about   the differences and i hope that you found  it useful if you liked the video leave us a   like and i hope to see you in another edition of  hub bytes until then take care and stay safe bye you

Channel: Psychiatry Simplified - Dr Sanil Rege

Views: 129,203

Keywords: adhd, dexamphetamine, ritalin, methylphenidate, adderall, vyvanse, stimulants for adhd

Id: w44BXLATt5w

Length: 8min 43sec (523 seconds)

Published: Sun Apr 03 2022