Ethanol and Methanol Flashcards
what are the medicinal uses of ethanol?
very limited- antiseptic, analgesic, weak general anesthetic
what is the structure of ethanol?
both lipid and water soluble, can get anywhere in body and act on any cell
what is the general action of ethanol on most cells?
depressant
what does ethanol do to the glutamine pathway?
ethanol inhibits the excitatory glutamine (NT) pathway
what does ethanol do to the GABA pathway?
ethanol activate the inhibitory GABAnergic (NT) pathway
what other pathway might ethanol activate?
dopanergic pathways- pleasure center
what are the sites of action of ethanol in the CNS?
ethanol inhibits higher cortical functions
inhibits critical faculties- increase in excitement, euphoria
lack of critical judgment- decrease social inhibitions
often memory impairment
slows reaction time
decrease visual acuity
decrease visual tracking ability
motor incoordination- staggering, speech slurring
impairs medullary function- loss of balance, nausea, vomiting, decrease respiration
decrease sexual performance
inhibits REM sleep
what are the sites of action of ethanol in the cardiovascular system?
skin vasodilation- due to inhibition of reflex vasoconstriction- why we feel warmer in winter but actually causing more heat loss
what are the sites of action of ethanol in the GI tract?
low concentrations- increase gastrin secretion, HCL acid secretion- good for digestion
high concentrations- gastric irritant
what are the sites of action of ethanol in the liver?
direct toxic effect on the liver
taking tylenol (acetaminophen)- interact with other liver toxicants
chronic use- fatty liver, decrease testosterone synthesis, increase testosterone metabolism
what are the sites of action of ethanol in the kidney?
weak diuretic- inhibit ADH secretion- water in collecting duct not absorbed
decrease uric acid excretion- can cause gout
what are the absorption characteristics of ethanol?
rapidly absorbed in small intestines
slightly absorbed from stomach
px with gastrectomies have more rapid absorption
carbonation may increase stomach emptying
what are the factors that delay stomach emptying (lower rate of absorption)?
exercise, food, anticholinergic agents
what are the distribution characteristics of alcohol?
rapidly equilibrated in all tissues
ethanol can pass through the placenta
newborns can undergo withdrawal- developmental damage- fetal alcohol syndrome
where is alcohol primarily metabolized?
in the liver
what are the oxidation reactions of ethanol?
ethanol is oxidized to acetaldehyde by alcohol dehydrogenase
acetaldehyde is oxidized to acetyl coa by acetaldehyde dehydrogenase
both steps transfer a hydrogen to NAD+ to make NADH
what is special about alcohol dehydrogenase?
it is a zero order reaction- rate of metabolism is constant, regardless to amount of ethanol
what is the average amount of metabolism pf ethanol?
1 ounce every 3 hours
what is the rate of limitation of ethanol metabolism?
amount of NAD+ limited
need to be regenerated via other means
what are the excretion characteristics of alcohol?
lungs (minor)
kidney (acetyl coa to water and co2)
breathelizer- lungs- accurate +/- 10%
best measure of alcohol exposure- blood test
what is the toxicity of alcohol?
potency is very low 50 grams of ethanol= 1mole of ethanol 4 average drinks= 56 grams aspirin- 1 mole=300 tablets 2 drinks = 0.03% blood concentration 0.08%= legal limit in ohio 6 drinks- 0.1% 12 drinks- 0.2% 18 drinks- 0.3%- unconscious
how do you gain tolerance of ethanol?
metabolic tolerance- increase alcohol dehydrogenase
tissue tolerance- increase # of excitatory neurons
behavioral tolerance- watching their slurring, staggering etc
what are the symptoms of physical alcohol dependence?
withdrawal- headache, dizziness, nausea, sweating- hangover
severe- tremors, nausea, seizures, cramps, delirum tremens (shakes, see things)
what kind of drug can ethanol interact with?
any drugs that enters the CNS
how does ethanol interact wth disulfiram?
inhibits aldehyde dehydrogenase
leads to build up of acetaldehyde
used to help people stay off alcohol
headache nausea, severe hangover if taken with alcohol
how does ethanol interact with acamprosate?
mechanism unknown- decrease the craving of ethanol
neurological and mental sequelae of ethanol addiction
brain damage, memory loss, sleep disturbances, psychosis, strain on family
nutritional sequelae of ethanol addiction
alcoholics have the poorest nutrition of any group in the us
drinking- calories from ethanol- develop thiamine deficiencies, wernicke’s encephalopathy- disorientation, polyneuritis, severe vision changes
cardiomyopathy sequelae of ethanol addiction
more congestive heart failure etc than control group
diet or not enough exercise?not sure
liver damage sequelae of ethanol addiction
cirrhosis/ fatty liver
fetal alcohol syndrome
CNS dysfunction, facial abnormalities, immune system abnormalities, still birth, spontaneous abortions
what are the oxidation reactions of methanol?
methyl alcohol is oxidized by alcohol dehydrogenase into formaldehyde
formaldehyde is oxidized by acetaldehyde dehydrogenase into formic acid
what is the toxicity of oxidations reactions of methanol?
metabolic acidosis
blindness- formic acid destroys ganglion cells in retina
how does the metabolism of methanol compare to ethanol?
slower
what is the treatment of the toxic formic acid?
ethanol
enzyme preferentially breakdown ethanol= no build up of formic acid - methanol is given time to be cleared first
fomepizole
specific inhibitor of alcohol dehydrogenase- prolong effect of ethanol
