Drugs- Alcohol abuse (linger) Flashcards
genes that incur risk to alcoholism?
ii) Some candidate genes for susceptibility to alcoholism include the dopamine D4 receptor,
the β1 subunit of the GABAA receptor,
and tyrosine hydroxylase (involved in the synthesis of dopamine, norepinephrine, and epinephrine)
which genes appear to protect against alcoholism
i) Some genes appear to protect against alcoholism, such as polymorphisms in alcohol dehydrogenase and aldehyde dehydrogenase
time to peak blood levels of alcohol with empty stomach
30 min
ii) Absorption occurs more rapidly from the small intestine than from the stomach
iii) The presence of food delays absorption by slowing gastric emptying
iv) Ethanol undergoes extensive first-pass metabolism by gastric and liver alcohol dehydrogenase (ADH)
metabolism of alcohol?
zero order (so independent of time and concentration)
iii) Small amounts of ethanol are excreted in urine, sweat, and breath, but metabolism to acetate accounts for 90-98% of ingested ethanol, mostly owing to hepatic metabolism by alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH)
(3) Gastric metabolism of ethanol is lower in women than in men, which may contribute to the greater susceptibility of women to alcohol (in addition to a lower total body water content)
how much alcohol per hour can the typical adult metabolize and why ?
7-10 g approximately 1 drink
(3) NAD+ requirements for alcohol metabolism
(a) 2 mol of NAD+ are required to convert 1 mol of ethanol to acetic acid (required by both ADH and ALDH)
(b) In terms of weight, 46 g of ethanol requires 1.3 kg of NAD+, which greatly exceeds the supply of NAD+ in the liver and is why the body is only able to metabolize about 7-10 g of alcohol per hour (zero-order metabolism)
alcohol dehydrogenase pathway
(2) ADH is a cytosolic enzyme that catalyzes the conversion of ethanol to acetaldehyde and is located predominantly in the liver (others include the stomach and brain)
(4) NAD+ is required to convert ethanol to acetaldehyde (this produces NADH, of which excess production may contribute to the metabolic disorders that accompany chronic alcoholism and to the lactic acidosis and hypoglycemia that frequently accompany acute alcohol poisoning)
(5) Aspirin inhibits gastric ADH and can increase ethanol bioavailability
(6) Fomepizole inhibits ADH and is used in the treatment of acute methanol or ethylene glycol poisoning (see below)
fomepizole
(6) Fomepizole inhibits ADH and is used in the treatment of acute methanol or ethylene glycol poisoning (see below)
Disulfiram
(4) ALDH is inhibited by disulfiram, a drug used for the treatment of alcohol abuse and dependence (see below)
what is an example of a certain polymorphism of ALDH and what happens in these individuals
(5) Genetic polymorphism of ALDH
(a) Some individuals of primarily Asian descent have a low activity level of mitochondrial ALDH
(b) When these individuals drink alcohol, they develop high acetaldehyde concentrations and may experience facial flushing, light headedness, palpitations, nausea, and general “hangover” symptoms
(c) Appears to protect against alcohol dependence and abuse
(d) Individuals with the polymorphism in ALDH who are chronic heavy drinkers and/or alcohol dependent have an increased risk of severe liver disease due to the toxic effects of acetaldehyde
what is the mechanism of action of the microsomal ethanol oxidizing system
(1) Mixed function oxidases (cytochrome P450s) use NADPH as a cofactor in the metabolism of ethanol to acetaldehyde
(2) At higher concentrations of ethanol (when NAD+ is depleted and the alcohol dehydrogenase system becomes saturated) there is increased contribution from the P450s, particularly 2E1, 1A2, and 3A4
(3) Chronic alcohol consumption induces MEOS activity (2E1) and can result in the enhanced activation of toxins, free radicals, and hydrogen peroxide
what happens when a person uses disulfiram
decrease in alcohol consumption b/c of side effects of nausea, chest pain, hyperventilation, tachycardia, vomiting
intoxication BAC level
0.08 %
50-100 BAC
Sedation, subjective “high,” slower reaction times
100-200 BAC
Impaired motor function, slurred speech, ataxia
at BAC above 100 depression of myocardial contractility has been observed
200-300 BAC
Emesis, stupor
300-400 BAC
coma
> 500 BAC
resp depression, death
effects of alcohol on NMDA
glutamate receptor
(a) Glutamate is the primary excitatory neurotransmitter in the CNS
(b) Receptor activation is implicated in many aspects of cognitive function including learning and memory
(c) Alcohol inhibits the ability of glutamate to open the cation channel of the NMDA receptor and leads to an increased depression of the CNS
(d) Memory loss that occurs with high levels of alcohol (i.e., blackouts) most likely results from inhibition of NMDA receptor activation
effects of alcohol on the GABA receptor
(a) GABA is the primary inhibitory neurotransmitter in the CNS
(b) Alcohol (like other sedative-hypnotics) enhances the effects of GABA on the GABAA receptor and leads to an increased depression of the CNS
effects of alcohol on smooth muscle
i) Ethanol causes vasodilation, likely due to CNS effects (depression of the vasomotor center) and smooth muscle relaxation caused by the metabolite acetaldehyde
ii) In severe overdose situations, ethanol can cause hypothermia caused by vasodilation
iii) Ethanol causes uterine muscle relaxation and was used intravenously for suppression of premature labor before the introduction of more effective and safe medications (e.g., calcium blockers, magnesium ion, β2-adrenergic receptor agonists)
effects of alcohol on the esophagus
(1) Alcohol is a factor associated with esophageal dysfunction, esophageal reflux, Barrett’s esophagus, traumatic rupture of the esophagus, Mallory-Weiss tears, and esophageal cancer
(2) At high BAC, decreased peristalsis and decreases lower esophageal sphincter pressure occur (may respond to proton-pump inhibitors and abstinence)
effects of alcohol on the stomach
(1) Heavy alcohol use can disrupt the gastric mucosal barrier and cause acute and chronic gastritis
(2) Beverages containing more than 40% alcohol have a direct toxic effect on gastric mucosa with clinical symptoms that include acute epigastric pain (relieved with antacids or histamine H2-receptor blockers