Pharm Flashcards
explain pharmacokinetics and pharmacodynamics.
what is the effect on drugs reaching their site of action?
pharmacokinetics: what the body does to the drug
– absorbs, metabolizes, excreted
pharmacodynamics: what the drug does to the body
– decreases pain, lower BP, improve function
distinguish chemical, generic and trade/brand names
chemical: N-acetyl-p-aminophenol
generic name (shortened chemical name): acetaminophen
trade/brand name: tylenol
steps of FDA testing and approval
- preclinical (animal) trials: 1-2 years
- clinical trials:
– phase 1: healthy volunteers <1 year
– phase 2: small patient sample 2 years
– phase 3: larger sample 3 years - approved for marketing
- post-marketing surveillance
odds of drug approval
for every 5,000 compounds that enter preclinical trials, 1 is approved
implications of drug testing/approval
drug costs
availability in US (looks at safety & efficacy) vs other countries (only look at safety)
failure to identify serious side effects
off label prescribing
prescription of a drug for a purpose that has not been approved by the FDA
40-60% of all prescriptions
legal? yes, FDA can’t tell physician how to practice medicine
dose-response relationship
no response if dose is too low
response appears at some “threshold” dose
response increases as dose increases until response plateaus (maximal efficacy/ceiling effect)
* dose-response curve
potency
related to the dose that causes a specific response in a specific magnitude
- drug that causes response at lower dose = more potent
- potency does not mean more effective
therapeutic index
indicates drugs safety
higher TI = safer the drug
TI = dose w/ toxic effect / dose w/ benefits
what is an acceptable TI?
no fixed guidelines
some drugs may have a lower number and produce serious side effects but the benefit outweighs the side effects (i.e. cancer drugs)
what is the ADME stand for in pharmacokinetics?
absorption
distribution
metabolism
excretion
absorption of pharmaceutical agents
drugs that typically move from site of administration into another tissue or central component (bloodstream)
directly related to route of administration
what are the two routes of administration?
enteral (oral, lingual, buccal, rectal)
– fairly simple, easy, less predictable absorption (lots of hurdles)
parenteral (injection, inhalation, topical, transdermal, others)
– more difficult, inconvenient, more predictable absorption (administered at site)
bioavailability
percent of administered dose that appears in bloodstream
ex: if 100 mg taken orally and 50 mg appear in bloodstream –> 50% bioavailable
– 100% bioavailable if given IV
some of the drug is destroyed during the “first pass” thru the liver
distribution of pharmaceutical agents
drugs cross membranes and tissues to reach target site
affected by:
administration route
physicochemical properties of drug
binding to plasma proteins
various barriers and carriers
volume of distribution
Vd = amount of drug administered / concentration in plasma
Vd = 42 –> even distribution throughout body
Vd < 42 –> drug retained in plasma
Vd > 42 –> drug retained in tissues
metabolism of pharmaceutical agents aka biotransformation
active form of drug is changed chemically to an inactive or less active byproduct or metabolite
creates a more polar, water soluble metabolite that can be excreted by kidneys
primary site of metabolism: liver
others: lungs, kidneys, GI tract, skin
enzymes metabolize the drug via;
phase 1 rxns: oxidation
phase 2 rxns: conjugation
excretion of pharmaceutical agents: sites
primary site: kidneys
other significant sites: lungs, GI tract
minor sites: sweat, saliva, breast milk
excretion of pharmaceutical agents
kidneys usually excrete metabolites after biotransformation in liver, other organs
25-30% drugs excreted “intact”
urine pH can affect excretion
how will some physical therapy interventions affect pharmacokinetics?
timing of rehab session with drug peaks and troughs (related to how pt feels during session)
effects on absorption/distribution:
– increased by heat, exercise, massage
– decreased by cold
help recognize improper drug responses (we get them doing things they’re normally not doing)
