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PSYD35H3 (12)
Chapter 13

Chapter 13 notes, detailed

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University of Toronto Scarborough
Nussbaum D

PSYD35- A Primer of Drug Action, 12 Edition CHAPTER 13- ALCHOHOL & INHALENTS Ethanol  Second most widely used psychoactive substance in world (after caffeine)  Absorbed rapidly orally Absorption  Ethyl alcohol is a two carbon molecule—in “liquors alcohol present in 40-50% concentration (proof= x2 conc.)  Soluble in water and fat—diffusing easily across membranes  Rapidly and absorbed completed from GI—time from last drink to max conc. In blood ranges 30-90 min. Distribution  Evenly distributed thought out all body—BBB very permeable to alcohol  Fetal levels are same as host levels Metabolism/Excretion  95% alcohol metabolized by AD (other 5% excreted unchanged)  ~85% metabolism occurs in liver; 15% by gastric AD in stomach lining (decreasing BAL by ~15%)  Metabolism of alcohol by gastric AD= FIRST PASS METBOLISM  Women have 50% less gastric metabolism of alcohol because of lower AD enzyme (so BAL is about 7% higher than males)  Men have greater muscle: fat than women (fat has little blood); alcohol is more diluted in men  Women with higher body fat (fat contains little alcohol) concentrate alcohol in blood plasma  Breakdown of alcohol: AD (when in the presence of the coenzyme NAD) converts alcohol to acetaldehyde; NAD is the rate limiting factor: AD+ ethanol +NAD= acetaldehyde and NAHD Enzyme AD converts acetaldehyde to acetic acid: AD+ acetaldehyde= acetic acid, NADH (disulfiram/Antabuse inhibits this enzyme—causing increase amounts of acetaldehyde which gives crappy side effects and reduces likelihood of drinking Acetic acid broken down into C02 and water, releasing energy: Acetic acid+ ATP=cO2, h20, AMP  Fairly constant rate of 1014mm of 100% blood metabolized per hour= ZERO-ORDER METABLISM; whereas first- order metabolism is amount of drug metabolized depends on amount in blood stream  1 hour to metabolize 40% whisky, bottle of beer, glass of wine  Injecting more than what is metabolized in an hour= BAC increases  Gram %= g/l/hour  Driving abilities minimal impaired at 0.01%; 0.04-0.08% increased judgment and RT impairment—accidents increase x4; BAC 0.10-0.14% 6x accident; BAC 0.15% 25x accident  Long term use, alcohol can induce drug-metabolizing enzymes in liverincreasing rate of metabolism (tolerance)  Chart on BAC page 437  Biological markers are being developed that can detect alcohol use even if BAC is 0 by detecting minor metabolites (ethyl glucuronide, ethyil sulfate) of alcohol that are present 80 hours after drinking PHARMADYNAMICS  Both water and lipid soluble dissolving in all tissues, distorting/perturbing membranes similar to action of general aesthetics  Results in nonspecific and indirect depression of neuronal function  GLU Receptors: ethanol inhibits function of NMDA receptors but disrupting responsiveness Over time up regulation of NMDA receptors, thus during withdrawal excessive excitations= dangerous seizures Drug acaptostate is structurally analogue of GLU it’s an anti-craving drug (acts with NMDA receptor increasing hyperexcitablity)  GABA Receptors: ethanol activates GABA mediated increase in Ch ion glow= greater inhibition low doses of ethanol act to reduce anxiety/panic (which can lead to dependence because of reinforcing GAG agonist effects) GABA inhibition activates opioid receptors that activate rewarding dopamine neurons Alcohol’s behaviour effects may be exerted through GBABA receptors on dopamine cells in VTA Ethanol binds to different subunit on GABAa receptor then do other GABA agonists—chronic alcoholism can affect gene expression—affecting other NT systems---GABA agonist action has been linked to positive reinforcing effects of the drug  Opioid Receptors: dependant people and offspring may have deficit in brain opioid activity; ethanol may cause opioid release which triggers dopamine release in brain reward system Naltrexone bocks opioid release and reduces alcohol cravings  Serotonin Receptors: 5H dysfunction may play role in some types of alcoholism 5HT2 and 5HT3 located on dopamine neuron is in nucleus accumbens and play central role SSRI reduce alcohol drinking in addicts of lower risk/severity  Cannabinoid Receptors: chronic intake of ethanol stimulates formation of anandamine NT for cannabinoid receptors This NT activates receptor and (With continual injection) leads to down regulation of receptors—responsible for tolerance, dependence, and craving Mice inbred to lack these receptors don’t voluntarily consume alcohol and lack alcohol-induced-dopamine mediated reward responses Administration of drugs that block these receptors prevents relapse PHARMACOLOGICAL EFFECTS  Reversible depression of mental functioning and cognition  Alcohol is anticonvulsant  In CNS, effects are addictive with those of other sedative-hypnotic compounds ( benzos, MJ)  Effects circulation and heart; alcohol dilates blood vessels in skin, decreasing body temperature  Low dose daily: reduce risk of arterial disease—alcohol increases HLD in blood and decreases LDL  Light to moderate dose of alcohol have also been showed to reduce the incidence of stroke PSYCHOLOGICAL EFFECTS  See chart page 443: basically up to 0.4 minimal changes; .05- .11 Intoxication; .12-.20 gross intoxication; .20-.28 stupor; .28-.36 blackout; .36-.41 sleep; .41-.52 death  BAC 0.05-0.09: social, talkative, decreased inhibitions, judgment  BAC 0.25-0.3: Ability to make memory is impaired (blackout(  Alcohol implicated in more than 50% of all homicides and assaults  Alcohol reduces anxiety (and consequences of aggressive behaviour) by dopamine activation, impulse control is reduced and increases likelihood of aggression  Alcohol myopia: short-sightedness, superficially understand, immediate actions have disproportional influence on behaviour and emotion  Study: 42000 adults surveyed; relative to those who didn’t begin drinking until 21+, those who drank before 17 were 3-4x likely to have had a fight after drinking: early onset drinking associated with alcohol related violence  Over 50% of all motor accidents are alcohol related  Chronic alcohol is associated with severe executive function deficits; and existence of theses deficits can affect capacity to maintain abstinence  Study in teens: recent detox in alcohol dependant teens associated with poor visual spatial functioning; alcohol withdrawal early in life was associated with poor retrieval of verbal and nonverbal info (working memory) TOLERENCE & DEPENDANCE  Metabolic tolerance: liver increase amount of drug metabolizing enzymes (accounts for 25% of tolerance)  Tissue/functional tolerance: neurons adapt to amount of drug present (so amount of drug need to show behavioural signs is ~2x that of no tolerant drinkers)—person appears less intoxicated so, but this doesn’t mean tolerance to cognitive/memory effects  Associative/contingent/homeostatic tolerance: environment can counter effects of alcohol  Blocking seizure activity ( usually up to 6 hours following withdrawal) is a major goal of detox and involves 2 classes of drugs: benzos and anticonvulsants  Kindling model for withdrawal: repeated alcohol withdrawals may lead to increase likelihood of withdrawal seizures  Study: neurobeh changes that can affect craving: patients who experienced multiple detoxes had higher scores on tests that measured obsessive thoughts, urges, and behaviours  Alcohol detox may be better managed with anticonvulsant mood stabilizers than benzos  Alcohol withdrawal syndrome: hallucinations, motor agitation, confusion, disorientations, sleep disorders— delirium tremens Study: assessed dopamine receptor response in alcoholics during usual consumption and after detox; detox was slowed recovery of dopamine receptors dopamine system may be involved in dependence and withdrawal SIDE EFFECTS & TOXICITY  Reversible drug-induced dementia: clouded sensory with distortions, insight, judgment problems, anterograde amnesia (blackout)  BAC +0.31 has 50% chance of blackout—by blocking memory protein formation needed for LTM  At high doses hallucinations and delusions can happen  BA
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