PYB260 2024 Week 10 Alcohol Lecture Notes PDF

PYB260 PSYCHOPHARMACOLOGY OF ADDICTIVE BEHAVIOUR Week 10: Action & Effects of Alcohol Melanie White, QUT 1  Lecture Outline What is alcohol? History Administration, distribution & excretion Effects of alcohol – physiological & perform...

PYB260 PSYCHOPHARMACOLOGY OF ADDICTIVE BEHAVIOUR Week 10: Action & Effects of Alcohol Melanie White, QUT 1  Lecture Outline What is alcohol? History Administration, distribution & excretion Effects of alcohol – physiological & performance Conditioning, tolerance & withdrawal Harmful effects Pharmacotherapies for alcohol dependence/ relapse prevention  Reflection Questions (egs, not exhaustive) You and your friend weigh the same amount, of different sexes at birth, and they appear to show less acute effects. If you are both light, social drinkers, what are some of the factors that might explain this difference (thinking about possible differences in absorption rates, distribution, or excretion)? If you knew your friend had experienced alcohol dependence for some time, what types of metabolic differences might explain this? What are some long-term effects of this alcohol use? If your friend experienced alcohol withdrawal, what does this look like? Describe at least one form of psychopharmacological treatment for ceasing their alcohol use? Describe at least one neuropharmacological effect of alcohol that leads to greater inhibition  What is alcohol & how do we measure it?  What is Alcohol? Isopropyl Methanol Ethanol  What is Alcohol? (cont.) Fermentation Sugar dissolved in water Yeasts multiply & convert sugar into ethanol & CO 2 Alcohol content about 10-15% Distillation Fermentation → heated → alcohol given off in vapour → vapour cooled Alcohol content ~ 40-50%  Measurement of Alcohol BAL/BAC: concentration of alcohol in whole blood Usually mg alcohol/100ml whole blood (or % of alcohol in the blood) E.g., 50mg/100ml = 0.05% SI units mmol/l mg/100ml / 4.607 = mmol/l Measurement of Alcohol 9 10  History of alcohol use Been around since the dawn of time 6000 BC – Neolithic people cultivated grains & grapes 3500 BC – Egyptian Book of the Dead 2225 BC – Code of Hammurabi (Assyria) Roman Empire – introduced grapes to Britain Taverns & alehouses established in Britain 1066 – wine reintroduced to Britain  History of alcohol use (cont.) Spirits first distilled about 1000 years ago 16th century – Irish settlers in Britain introduced distillation 1660 – licensed distilleries (esp. gin) 1684-1727 – consumption from 0.5 million to 3.5 million gallons/yr 1742 – distillation banned Laws relaxed over next 50 years American Colonies American Revolution = relaxed regulation of alcohol production & sale Late 1890’s: Temperance Movement WW1: licensing hours introduced to control factory workers  History of alcohol use (cont.) Prohibition 1917 – 18th Amendment Prohibition resulted in increased organized crime & had little support – Al Capone 1933 – Roosevelt amends constitution to void 18th amendment (21st amendment) Consumption ↑ until 1980s when it began to drop again as people became more aware of the harmful effects of alcohol Trends in type of alcohol consumed in Australia Australians 14+ Alcohol Drinking Status Risky alcohol consumption trends in Australia Risky alcohol consumption trends by remoteness  Most recent Australian stats (2022-23): Alcohol accounted for 59% of drug-related hospitalisations; 58% of those were males 1,742 alcohol-induced deaths (1,245 males; highest rate for 55-64 yr olds); 91% related to chronic conditions (incl alcoholic liver cirrhosis); acute alcohol-induced deaths (154 deaths) highest in 45-64 yr olds. Alcohol most common principal drug of concern (43% of treatment episodes) – consistent since records began (2002-03) Where alcohol was the principal drug of concern (AIHW 2024): 3 in 5 clients (60%) were male & 1 in 6 (16%) were First Nations people 1 in 2 clients were aged 30–39 (25% of clients) or 40–49 (26%) most commonly referred by self or family (41% of treatment episodes), followed by health services (37%) most common main treatment type was counselling (33% of treatment episodes), followed by assessment only (23%) and withdrawal management (14%) The median treatment duration for alcohol was just under 4 weeks (27 days) https://www.aihw.gov.au/reports/alcohol/alcohol-tobacco-other-drugs-australia/contents/drug-types/alcohol#keyfindings Administration, absorption, distribution & excretion of alcohol  Absorption, Distribution & Excretion Administration & absorption Generally oral administration Molecules cannot be ionized pH levels have no effect on absorption Readily dissolves in water & passes into blood from stomach lining, intestines, & colon 1st pass metabolism – alcohol dehydrogenase in stomach  Absorption, Distribution & Excretion Absorption rate & BAL affected by: Stomach contents Body fat, age Female sex:  alcohol dehydrogenase in stomach  body fat Medication – H2-receptor antagonists reduce alcohol dehydrogenase Concentration of alcohol in beverage Usage (abstainers vs. regular users)  Absorption, Distribution & Excretion Absorption rates & BAL vary greatly between individuals, however in general: Plateau phase usually reached ~ 1 hr >consumption Peak levels ~ 15 minutes later (>start of plateau phase) But depends when readings are taken (i.e., after a few drinks, plateau & peak levels reached sooner than this). Drink type may also affect absorption Beer stays in stomach longer Absorption of sparkling wines facilitated by carbonation Higher concentration absorbed more quickly, up to a point ([~40% alc.]) Expectancy effects? (e.g., Cole-Harding & Michels, 2007)  Theoretical time course for BAL after taking a single drink. A: Absorption Phase B & C: Plateau Phase D: Excretion Phase Source: Text, Fig 6-2  Absorption, Distribution & Excretion Distribution Alcohol dissolves in water distributed entirely in body water Crosses blood-brain barrier & placental barrier Circulates through lungs & vaporizes in air (Breathalyzer) Excretion Some alcohol is excreted through breath, sweat & urine Most alcohol is metabolized in the liver (~90-98%) – at rate ~ 1 standard drink/hr  Absorption, Distribution & Excretion Alcohol is metabolized by the liver in a 2-step process: 1. Alcohol is converted to acetaldehyde by alcohol dehydrogenase 2. Acetaldehyde is converted into acetate; which escapes into bloodstream, some acetate then converted to acetyl-coenzyme A Acetyl-coenzyme A is then converted to water & CO2, via the Krebs cycle (or “citric acid cycle”)  Steps in the Metabolism of Alcohol Source: Text, Fig 1-9  Absorption, Distribution & Excretion Excretion rates vary greatly between individuals Typical range ~10-20mg/100ml/hr Rate of metabolism may depend on drinking experience Non-drinkers metabolize alcohol slightly slower Eating speeds metabolism of alcohol Excretion of methanol: Formaldehyde & formic acid  Absorption, Distribution & Excretion Microsomal ethanol-oxidizing system (MEOS) Also responsible for metabolism of alcohol  activity with continuous drinking  heavy drinkers metabolize alcohol more quickly → metabolic tolerance Also responsible for metabolizing barbiturates → cross tolerance Effects of alcohol  Neuropharmacology of alcohol Some interesting features of alcohol: 1. Alcohol affects a variety of tissues 2. Need large dose to have an effect 3. No drugs act as complete antagonists to all of the effects of alcohol  Conclude that alcohol does not work directly on specific receptor sites, but affects many sites of action  Neuropharmacology of alcohol Alcohol may affect receptors of many NTs & their ion channels Glutamate (excitatory NT) Alcohol  functioning at NMDA receptor (blocks ion channel) Chronic exposure → up-regulation of NMDA & glutamate Hippocampus (NDMA receptors) & PFC (glutamate & GABA neurons) Source: Text  Neuropharmacology of alcohol Alcohol may affect receptors of many NTs & their ion channels GABA (inhibitory NT) GABAA-receptor-ionophore complex (see text, Fig 7-1, next slide) Orthosteric & allosteric sites *– alcohol ↑ GABA effects ( neural activity) – so alcohol acts as a positive allosteric modulator cerebellum GABAB (metabotropic) receptors, esp. those that  DA release e.g., in VTA → less inhibition of DA release into Nacc Agonists (e.g., baclofen)  alcohol consumption, reinforcement, motivation & craving Chronic alcohol exposure leads to changes in this receptor too. 5-HT Alcohol stimulates 5-HT3 receptor (also important in releasing DA) *For an illustration, see http://www.nature.com/nbt/journal/v32/n11/fig_tab/nbt.3028_F2.html A schematic drawing of the GABA receptor-chloride ionophore complex (Fig 7-1 2013 Text; Fig 7-2 2018 ed.).  Neuropharmacology of alcohol (cont.) Alcohol also affects: second messengers monoamine oxidase glycine acetylcholine endogenous opioid systems  Effects of alcohol On the body: Dilation of blood vessels – flushing (but  body temp)  urination On sleep: Induces sleep, but does not  total sleep time (exception: chronic users:  insomnia)  REM (1st part of sleep at low doses, whole night at higher doses, tolerance ~ 3 days) REM rebound effects upon cessation  Effects of alcohol (cont.) On perception: At high doses  absolute & difference thresholds for vision  visual acuity (~.07 BAC)  peripheral vision  sensitivity to smell, taste & pain (~.07-.08 BAC) Subjective effects: Biphasic effect re time & dose – but not for everyone Stimulant-like effects may ≈ greater risk of abuse  Effects of alcohol (cont.) On performance ↑ (slowed) reaction time  hand-eye coordination (cerebellum)  speed & accuracy  vigilance  Memory (storage & retrieval) En bloc blackout Grayout  Sensitivity of organs in the inner ear responsible for balance (Romberg sway test for drink driving) %change in BAC levels & behavioural variables as a function of time since alcohol is administered (Grilly& Salamone, 2012, Fig 10.1)  Effects of alcohol (cont.) On behaviour Disinhibition Talkative, excitable, cheerful Sleepy, unconscious Nausea, vomiting On driving Impairs driving performance ~.05 -.08 (lower for many) Reflected in crash statistics Relative risk of being involved in a traffic accident, by BAL Fig 6-3 text Fig 6-4 text The risk with a BAL less than 1.0 mg per 100 ml blood (i.e., BAL8-12 hours Agitation, tremors, muscle cramps, vomiting, nausea, sweating, dreams, etc. Usually over