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4. CNS depressants.docx

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Kristin Hillman

CNS Depressants – Week 4 8/23/2013 2:23:00 PM Quiz next week – starts 9am 20mins test Why use a CNS depressant? (class brainstorm)  E.g. valium, Xanax, ambien, rohypnol, GHB  Counter stress  Reduce anxiety  Sedative (sleepy/drowsiness)  Recreational (e.g. Xanax = happiness effects)  [Weaning for addiction] = valium  there are more specific drugs for this  Insomnia  Date rape (e.g. rohypnol)  Unintentional consumption  [Schizophrenia] = valium  there are more specific drugs for this Primary uses:  4 primary uses for CNS depressants: o 1. To reduce anxiety o 2. To facilitate sleep (i.e. sedative/counter insomnia) o 3. To reduce awareness/consciousness  therapeutic = anesthesia  malicious intent  4. To reduce muscle spasms or associated pain o Talked about last week  Oral muscle relaxers (also CNS depressants) 1. To reduce stress: What is anxiety?  Defined by dictionary = o 1. Distress or uneasiness of mind o 2. State of apprehension and psychic tension  It is essentially “nervous energy” o Everyone experiences it…  What causes it? o Anxiety is a natural response to certain situations o Acuity it is ok to be anxious  Some argue beneficial (when you are anxious it cognitively primes you to do things such as study for exam or something…it drives performance)  Can help memory…but when it goes on a long time it can impair it o Chronic anxiety becomes problematic  Get mood changes  Impairs memory (not good)  Get sick more  Irritability, pessimism, dysphoria, lack of concentration, physiological effects  Drug that reduces it?  Anxiolytic History of CNS depressants/anxiolytics:  CNS depressants have been used throughout civilization…  Can we think of any drugs that people have used to chill out and reduce tension? o Apiates o Alcohol o Cannabis o Psychedelics (e.g. scopolamine) o Tobacco (e.g. nicotine) o All of these give some contented euphoria  People have been using drugs for a long time to reduce stress  1850s – 2000s What is a CNS depressant?  It‟s a drug that depressed your CNS activity  CNS functions to: o 1. Receive info from PNS (the outside world) o 2. Integrate and understand info o 3. Initiate appropriate response  When you take a CNS depressant you start to decrease all of these functions.  CNS and PNS systems work but talking to each other, neurons need to be excitable  these  Pharmacology angles for depressants:  Decrease excitation – how? o By dercrasing glutamatergic tone  Glutamate (Glu)  Increase inhibition – how? o By increasing GABAergic tone o Main approach – CNS depressants by and large increase GABAergic tone in the CNS  (GABA) Glu and GABA:  You don‟t want too much inhibition or hyperexcitation o It‟s a very fine balance that your brain has to try and keep – use Glu and GABA to do that  These are primary neurotransmitters  For many years, these chemicals were not accepted as neurotransimtters  Neurotransmitter system criteria: o They were figured out later that they do fit the criteria o They are amino acids and derivatives Glutamate (Glu)  Synthesis: o Derived from glucose or glutamine  change that to glutamate  Storage and release: o Loaded via vesicular glutamate transporters  Postsynaptic Glutamate receptors: o 4 different subtypes:  NMDA – ionotropic (i.e. excite the cell)  Kainate – ionotropic  AMPA – ionotropic  mGlu – metabotropic (i.e. inhibit the cell)  Note: mGluRs (of Gi variety) can be presynaptic  Need to get rid of it so it doesn‟t excite the cell constantly, Clearance:  Reuptake via high-affinity glucose transporter (which is called GLUT) – o can also have EAAT (excitatory amino acid transporter) type of transporter – picks up more general things GABA:  Synthesis: o Derived from glutamate  Need GAD and B6  Receptors:  GABA (A)  GABA (B)  GABA ©  Clearance:  Depolarizing  Important role of glial If whole goal is to get more GABA in your system, why don’t you just drink some GABA?  No – GABA doesn‟t cross the BBB o BBB can stop things coming in, but also stops things going out (stops GABA from going out which is good,  Think about synapse because that‟s where all out drug targets are.  What are the alternative approaches? o synthesis o release o post-synaptic receptor activity o clearance and metabolism CNS Depressant Mode of Action:  If keep increasing the GABAergic tone  (it is dose dependent, if you have too much in the system you will reach death)  Think of it as a scale: o Anxiolysis o Sedation o Sleep o Unconsciousness o surgical anaesthesia …..  A lot of the time we talk about CNS depressants as sedatives, or sometimes tranquilizers (terminology) History:  CNS depressants have been used throughout civilization…  Bromides first widely used sedative o half life, take on the half life = these drugs had a very high toxicity effect (remember graph that goes up and up…that‟s what happens here)  Chloral hydrate was the next widely marked sedative  Mickey Finn o Used to date-rape people by dropping this into girls drinks o nowadays, known as "slip someone a Mickey" o can actually find this still being used  typically in rest homes, in age-related dimensia cases so that people don‟t get up in the middle of the night etc. Barbiturates introduced:  Don‟t remember all  Should be able to give ONE example of this…memorize one of the names o e.g. Phenobarbital = first used  120 hours half life (take every 5 days) – not that convenient so making drugs with shorted half lives were good  The way they work =  They depress motor cognitive and behavioural functioning o DOSE-DEPENDANT effects  Can lead to death if a lot is taken – refer to spectrum before…  there were thousands of deaths from taking these - not good drugs, safety profile wise...  They facilitate the GABA (A) receptor opening  Site of Action  GABA drugs can work everywhere in your system  they act throughout the CNS  when you start to depress activity in the brainstem, you also depress your heart rate and your respiratory rate drops off- this is how it can kill you.  Side effects??  Your reaction time  cognition - learning and memory is impaired  biggest side effect is death Barbituates:  they exhbit a lot of tolerance o there are 2 types of tolerance:  1. Pharmacodynamics tolerance  2. Pharmacokinetics tolerance  activity of enzymes upregulate, so it increases the own drugs metabolism (have to keep taking more to get effects)  Can exhibit abuse and dependence  Have physiological effects = mostly sleep related = major sleep disturbances) o when go off drugs can affect sleep  Also have psychological effects = desire for effect  Therapeutic window  Small window, therefore quite quickly you start to go into toxicity range  Mainstay of sedative prescription up until 1960s, but today not readily prescribed as anxiolytics due to safety issues.  still around today used for: o anticonvulsant for epilepsy o operative sedation/anesthesia o death o truth sera?  Is there a drug that can make you tell the truth? o Some believe truth serums will come back – David Brown, Washington Post 2006 Truth Serum?  Why would you take such as drug? Who would use it?  Court of law to maybe get a confession  In a psychiatric sense  Military for interrogation purposes  For sports – get a confession for drug-taking instead of spending all this money on testing  Are there any truth sera available today?  Potential compounds that have been investigated in the past o Alcohol? o Sodium Amytal? o Scopolamine? – from reading o Oxytocin? o LSD/mescaline  Is it ethical to administer such a drug to another person?  Maybe if you sign consent to it…it could prove innocence etc?  Could it be used in a malicious way?  Interrogation etc  Could it be used in a positive way?  Life/death reasons?? – e.g. kidnapped child  Do we have a truth serum today = NO  Clinical records for narcoanalysis found in psychiatry:  1930s – William Bleckwenn demonstrated potential for amytal to treat catatonic mutism (e.g. stuttering etc)  1940s  Today - very contentious amongst medical professionals  There has also been this military drive to use this in prisoners of war etc.  At early stages of CNS depression, many people do become more talkative  does this mean they are telling the truth (filter goes away when you get drunk, but that doesn‟t imply truth) – need to think about this. Meprobamate (Miltown):  1950s  One of the most first prescription drugs to be widely marketed, with targeted campaigns towar
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