L23 Flashcards
Diagnostic criteria for alcohol use disorder
- Impaired control
- Social impairment
- Risky use
- Pharmacological criteria
Alcohol metabolism ethanol
Ethanol
↓ alc dehydrogenase (cyto)
Acetaldehyde (toxic and reactive)
↓ aldehy dehydrogenase 2
↓(mito)
Acetate
Enzymes involved in alcohol metabolism
- Alcohol dehydrogenase
- CYP2E1
- catalase
- aldehyde dehydrogenase2
Enzymes involved in alcohol metabolism
alcohol dehydrogenase
- cytosol
- class I ADH is most important
- primarily found in the liver
- zero-order kinetics - 7~10g/hour
Enzymes involved in alcohol metabolism
CYP2E1
- microsome
- minor but becomes important at elevated alcohol concentrations
- induced in chronic heavy drinkers
Enzymes involved in alcohol metabolism
catalase
- peroxisome
- an important antioxidant enzyme - removes hydrogen peroxide
- H2O2 + H2O2 → 2 H2O + O2
- oxidise alcohol (e.g., in the brain)
- CH3CH2OH + H2O2 → CH3CHO + 2H2O
Enzymes involved in alcohol metabolism
aldehyde dehydrogenase 2
- mitochondria
- converts acetaldehyde to acetate
thiamine (vitamin B1)
- phosphorylated form (thiamine pyrophosphate, TPP) is a cofactor for enzymes involved in meta of carbohydrates (slide)
Alcohol, thiamine deficiency,
- malnutrition from poor diet
- ↓ absorption in the GI tract (thiamine transporter SLC19A2/3)
- ↓ storage in the liver due to liver damage
- ↓ uptake and impaired utilisation of thiamine in cells
Wernicke-Korsakoff Syndrome (WKS)
- Wernicke’s encephalopathy (acute phase)
- Korsakoff’s syndrome (chronic phase)
– alcohol-induced neurocognitive disorder (DSM-5)
- Korsakoff’s syndrome (chronic phase)
alcohol-induced neurocognitive disorder (DSM-5)
Effects of thiamine deficiency
–ataxia - affects gait and stance
–nystagmus - uncontrolled eye movement
Early age drinking associated with increased likelihood of lifetime alcohol dependence
- early maturation of limbic regions, e.g.,NAc- critical for processing of rewarding stimuli
- delayed maturation within PFC regions - critical in inhibitory control and other executive functions
Alcohol and dopaminergic transmission steps
- Alc stim the release of endogenous opioid peptides in VTA
- Alc enhances GABA(a) receptor activity
- Alc inhibit release of glutamine from nerve terminals -> (/)
- (1&2) -> inhib Gaba interneurons -> disinhib VTA DArigic neurons -> enhance DAergic transmission in NAc(/)
benzodiazepines outcome
relieve acute withdrawal symptoms
disulfiram outcome
- maintain abstinence
acamprosate outcome
- maintain abstinence
naltrexon outcome
- block pleasure and reward
Benzodiazepines
- long-acting benzodiazepines are preferred
- anticonvulsant/anxiolytic
- short-term; gradual cessation of drugs as
withdrawal effects are similar to alcohol
Disulfiram info
- metabolites of disulfiram irreversibly inhibit aldehyde dehydrogenase
- prevent conversion of acetaldehyde to acetate
- Increase in ace-hyde→ unpleasant symptoms, e.g., flushing, dizziness, nausea and headaches
- used in motivated individuals after detoxification and under supervision (not act. drinkers and in conjuc iwth behavioural interventions)
Acamprosate
- oral calcium salt (Bio-11)
- not hepatically meta, and excreted unchanged in urine and faeces
- Mod GABA and glutamate (might be main one)
- Dose adjusted for renally impaired
- Diarrhoea common, nausea, vom, rash, abdo pain
Naltrexone
- an opioid receptor antagonist (binding affinity: µ > k > delta)
- hepatically metabolized by dihydrodiol dehydrogenase: 6-β-naltrexol
- Oral tablets
- not suitable for current opioid users/on opioid maintenance bc of WD
- nausea, headache, dizziness, fatigue, insomnia, vomiting, and anxiety
thiamine deficiency distinct brain lesions
thalamus –> amnesia
mammillary bodies –> confabulation
hippocampus –>confusion
pons: ataxia - affects gait and stance
cerebellum: nystagmus - uncontrolled eye movement
