Drugs - Metabolism and stuff Flashcards
Warfarin - Cytochrome
2C19
Steady state kinetics
Takes 5 half-lives to achieve, then 5 half-lives to clear
Most protein bound drugs
Phenytoin, fosphenytoin
Antidotes:
INH
Organophosphate
INH: Pyridoxine
Organophosphate: Atropine
Toxic alcohols
Methanol - AG, osmolal gap. Blindness, formic acid.
Ethanol - AG, osmolal gap. Respiratory depression, acetate.
Isopropanol - Osmolal gap.
Ethylene glycol - AG, osmolal gap. Oxalate crystals.
Zero-order kinetics drugs
Phenytoin
Ethanol
Aspirin
Volume of distribution
High for lipophilic drugs. The theoretical volume in which the drug would need to be distributed to match the PLASMA concentration.
Drug testing methods
Screening: Immunoassay
Confirmatory: Chromatography + mass spec
Cocaine
Coronary vascoconstriction, MI, septal perforation. SNS prodrome.
Benzoylecgonine
Opiates
Pinpoint pupils, bradycardia/hypotension.
Many metabolites…
Whole blood ethanol
Tends to run lower than serum or plasma ethanol. Conversion is difficult (depends on hematocrit)
Odors:
Garlic
Bitter almond
Mothball
Garlic - Arsenic, organophosphates
Almond - Cyanide
Mothball - Camphor
Lead poisoning
Inhibits ALA-D and ferrocheletase»_space; ZEP accumulates
Microcytic anemia with basophilic stippling
Treat with dimercaprol
Carbon monoxide
Cherry-red appearance. Levels up to 2-6% normal in smokers.
Pulse oximetry may yield normal result–use co-oximetryh.
Cyanide poisoning
Cyanide inhibits cytochrome A3»_space; severe lactic acidosis
Treat with amyl nitrite»_space; forms methemoglobin
Salicylate poisoning
Metabolic alkalosis with vinegary smell
Also causes respiratory alkalosis
Arsenic poisoning
Inhibits oxidative phosphorylation.
Acute symptoms nonspecific. Rice-water diarrhea?
Organic arsenic is common in seafoods–harmless?
TCA poisoning
QRS prolongations, arrhythmias
Antichonlinergic effects: Dry/hot/mad
Digoxin
Primarily renally secreted.
Many cross-reacting substances.
Antidote: Fab fragments
Magnesium poisoning
Inhibits COMT, causing hypersympathetic picture. Resembles pheochromocytoma!
CYP inducers
Carbamazepine Rifampin Alcohol Phenytoin Smoking
CRAPS
CYP inhibitors
Ritonavir
Azoles
Grapefruit juice
RAG
What drugs are not commonly tested on screening immunoassays?
Oxycodone
LSD and derivatives
GHB
Mephedrone
Pseudocholinesterase assay
Diagnostic test for organophosphate poisoning
Mephedrone
Primary ingredient of bath salts
Cathinone, derived from Khat (related to amphetamine)
Serum separator tubes
May adsorb drugs; use red-top for drug monitoring
Codeine metabolism
Metabolized by CYP2D6 into morphine
