Toxicology Flashcards
general approach to the poisoned patient
- stabilization
- history
- examination (lab testing)
- diagnosis
- decontamination/enhanced elimination
- poison-specific treatment (Antidote)
- disposition
Toxidromes
group of signs and symptoms that are characteristically associated with a drug or class of drugs
preventing absorption or enhancing elimination of drugs
- none are universally applied
- techniques depend on state of patient and drug in question
mechanism of activated charcoal
toxins bind to charcoal and prevent absorption
whole bowel irrigation
cleanse whole bowel using PEG
- used esp if someone is a drug mule
how do we enhance renal elimination when enhancing elimination
make urine more acidic or basic depending on drug you are trying to eliminate
- if drug is ionized it will not cross cell membranes
> acidic drug for ex = ionized in a basic medium
> enhance elimination of acidic drug = try to make urine more basic bc if urine is basic, acidic drug will be ionized and it will not cross cell membrane and will not be reabsorbed
T or F. every drug has an antidote
F!
different mechanisms of actions for different antidotes
- antidotes that interfere with metabolism
> ex: Fomepizole interferes with the metabolism of methanol and ethylene glycol bc it inhibits alcohol dehydrogenase - interact with receptors
> preventing opioids from binding (ex: naloxone bonds instead of opioids = no effect) - shunting a particular pathway (different direction that what would normally cause intoxication)
- antagonist of receptor
- sop up all of the drugs
- chelating agents = bind to substance to help excrete it out of body
disposition
when we would consider transferring the patent to a higher-level facility
- if unable to stabilize
- patient deteriorates
- cant provide ongoing support
- timely diagnostic testing not available
- toxin-specific therapy is unavailable
- suicidal ingestions = Psych consult needed
which clinical toxicology testing is STAT
quantitative ( except trace elementS)
immunoassays for initial testing
- antigen-antibody rxns
- both instrument-based and non (POCT)
- detects broad class of drugs (not specific drug in a class though); can distinguish drugs between classes, just not within a class
- cross-reactivity dependent n reagent chem and devices used
- limited in scope
- prone to FNs and FPs
Define cutting agents
help with “bulking up” supply or dose of drug
- interferes with qualitative testing
This can cause a false positive with fentanyl immunoassays
trazodone
Cross-reactivity can be poor for these class of drugs
benzodiazepines
- some are more detectable than others
- oxaprozin = FP
confirmatory or definitive testing
- uses GC/MS or LC/MS/MS
- confirms immunoassay or initial testing for drugs with no immunoassay
- more resource driven
- provides high specificity
the action of the body on the drug
pharmacokinetics
Two reasons for therapeutic failure
- not taking medication (patient feeling ok so stop taking it OR side effects of meds is too much)
pharmacodynamics
the action of the drug on the body
- how does the drug interact with receptor systems to cause effects
indications for TDM (7)
- for drugs with a defined plasma therapeutic range
- when the toxic effects of drugs resemble the symptoms of the condition being treated
- for drugs with a defined plasma therapeutic range, but with great inpatient variability in elimination
- for drugs whose clinical effects are difficult to determine (not done for BP medications for example because can just measure blood pressure)
- complicating factors such as GI, CV, hepatic, or renal disease
- verification of patient compliance
- narrow therapeutic index
narrow therapeutic index
very narrow range for when a drug is effective vs when it is toxic
define steady-state
drug intake = drug elimination
MAKE SURE WHEN DOING TDM = do it at this plateau
- takes five half-lives to get to steady-state
- TDM too early = drug level is low; might say sub-therapeutic when not really…
half-life
the time required to decrease drug concentration by 50%
T or F. Different drugs have different half-lives
T!
time to achieve steady-state is influenced by
half life
steady-state concentration determined by
dose and frequency of dose
MEC
- minimum effective concentration
- the lowest drug concentration above which drug is active i most patients (or will produce an effect)
MTC
- minimum toxic concentration
- lowest concentration above which most patients are likely to experience adverse or toxic effects
therapeutic range
relationship between the desired clinical effect of a drug and the plasma drug concentration (MEC to MTC range)
therapeutic index
ratio between the plasma concentrations yielding toxicity and desired effects of the drug (MTC/MEC)
the highest drug concentration reached after a dosage
peak concentration
trough concentration
the lowest drug concentration reached, usually before the next dose is given
inter-patient variability = will afect pharmacokinetics
- age
- sex
- pregnancy
- drug interactions
- disease (ex: renal, heart disease, etc.)
- pharmacogenetics
- malnutrition (will affect GI absorption)
- patient compliance
major goals of TDM labs
- serve as a testing resource to health care professionals and the public
- provide excellent analytical service
- ensure analysis is done on appropriate specimens at appropriate time
- provide interpretation of results
- conduct research
