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Intro to Pharmacology

I do not take drugs, I am drugs.
--Savlador Dali


GENERAL VOCAB
pharmacodynamics = mechanism of action
pharmacokinetics = absorption, distribution, metabolization, elimination
drug = substance that alters function of organism
drug = molecule that interacts to cause biochemical and physiologic changes in organism
drug = chemical agent used in dx, tx, or prevention of dz
drug receptrs = macromolecules that bind drugs and mediate changes
bioavailability = fraction of drug that gets into systemic circ unchanged
half life = time for plasma concentration to decrease by 50% after discontinuation
loading dose = higher early doses to rapidly reach therapeutic serum concentration of drug
(used for siezure control, vitamin D)
maintenance dose = maintain steady state plasma concentration in therapeutic range
onset = time to effects of drug
duration = time that drug works
efficacy = degree to which drug induces maximal therapeutic effects, compared between classes
potency = amount rqd to produce 50% of max response, compared among same class drugs
(ex: morphine for muscle soreness: more potent but less efficacious than ibuprofen)
ED50 = drug concentration that induces clinical effect in 50% of subjects
LD50 = drug concentration that induces death in 50%
TI = therapeutic index = LD50/EC50, or deaths/effectiveness, a measure of safety
large value good = big gap between doses needed for beneficial effect vs death
narrow TI = dangerous drug, theophylline used 25 ya for asthma, causes GI upset, seizure
agonist = binds receptor elicits specific response
partial agonist = binds receptor elicits lesser response
antagonist = inhibits or blocks responses that would be caused by agonist
competitive antagonist = blocks receptor where agonist would go (irr/reversible)
noncompetitive antagonist = binds other site on receptor but still blocks action (irrevers)
physiologic antagonism = two agonists in unrelated reactions causing opposite effects
neutralization antagonism = two drugs bind ea other causing partial/complete inactivation
tolerance = decreased response-->need increased dose to get same effect
dependence = pt needs drug to fx "normally", observed at cessation-->withdrawal sx
addiction = no consensus definition
(Miller: "lifestyle characterized by compulsive use and overwhelming involvement with a drug")
OTC = available at supermarket, pharmacy, w/o restriction
BTC = behind the counter, dispensed by pharmacist without prescription from doc
POM = prescription only medicines = can't get w/o a scrip from a licensed medical pro
generic = drug whose patent has expired and anybody can manufacture and cell product

REGULATION OF DRUGS AND SUPPLEMENTS
FDA = US Federal Food, Drug, and Cosmetic Act of 1938 created this
DSHEA = Dietary Supplement Health and Education Act of 1994: FDA regs supps as food not drug
supplement = product intended to supp diet and contain one or more of: vit, mineral, aa, protein, herb, botanical, concentrate, metabolite, constituent, extract, combination of these
supps "may not claim to treat, diagnose, cure, or prevent disease"
supp manufacturers may make "structure or function claims" re health benefit of product
IND = investigational new drug phase, early testing for drug efficacy and safety
after IND approved, more phases:
phase I: clinical pharmacology phase, n=20-80, 6-12mo
phase II: controlled studies in pts with dz/condit drug is to tx, n=100-200, 1-2yrs
phase III: multi-ctr controlled trials, n=600-1000, 3yrs average
NDA = new drug application follows all phases, presents preclinical/clinical data
incl all published reports of experience with the drug
(what about unpublished reports? don't publish anything that doesn't sell your drug!!)
FDA approval in NDA stage average 24 mo, range 2mo-7yr
phase IV: post marketing surveillance assesses risks not seen in earlier trials
also assesses expansion of indications for use

FDA/DEA CLASSIFICATIONS
CI = not approved for medical use
CII = high potential for abuse
CIII = moderate potential for abuse
CIV = low potential for abuse
OTC

FDA USE IN PREG RATINGS
A = controlled studies show no risk
B = no evidence of risk in humans
C = risk cannot be ruled out (mc)
D = positive evidence of human fetal risk
X = contraindicated in pregnancy

ROUTES OF ADMINISTRATION
enteral = taken in by GI system
PO = oral = drug that withstands acidity, permates the gut lining to get into hepatic portal circulation-->first pass through liver-->systemic circulation
(pts on PPIs have less acid so drugs that depend on acid are poorly absorbed)
(diabetics often have delayed gastric emptying, affecting drug absorption
parenteral = injx (beyond GI), rapid and predictable absorption, unconcious/vomiting no prob
(disadvantages of parenteral: aseptic technique rqd to reduce infx, SEs: pain & local irrit, can't give insoluble drugs, can't "take back" a dose)
intrathecal = inside the spinal canal, in the CSF
SC or SQ = subcutaneous
drug "depot" = pocket of drug usu in oil base administered usu IM for slower absorption. (Hormones administered this way may be absorbed over 3-12 months, commonly testosterone, progesterone.)
SL = sublingual
IV = intravenous or intravascular tho arteries rarely used dt risk of bleed
topical
transdermal patches
inhalation
drug eluding stents = ??? OH the word is "eluting"

DRUG ELUTING STENT =
a coronary stent (a scaffold) placed during angioplasty into narrowed coronary arteries
slowly releases a drug to block cell proliferation-->prevent stenosis-->lower clotting-->less blockage via restenosis
((HOW IS THIS DRUG ELUDING?))
approved by FDA after proven statistically superior to bare-metal stents (BMS) for tx of CAD
less MACE = major adverse cardiac events
MACE = clinical endpoint of death + MI + repeat intervention dt restenosis

DRUG ABSORPTION FACTORS
ionization state (non-ionized = lipid soluble = more absorbable)
molecular weight (lower = smaller = more absorbable)
solubility (lipid soluble = uncharged = can diffuse through membranes, can't pee it out)
formulation (solution, tablet, etc)
weak bases po absorbed in small bowel
weak acids absorbed in stomach

DRUG DISTRIBUTION
movement from one compartment of body to next
lidocaine goes from area of injx to systemic circ (bad for local)
add epi to lidocaine to vasoconstrict local tissue and keep drug at site, reduce bleeding
don't add epi to sensitive tissues (penis, ear tip, etc) lest you loose them

ELIMINATION
drugs usu eliminated by biotransformation (liver) and/or excretion into urine or stool
kidneys can't eliminate lipid soluble drugs, they are reabsorbed
phase I detox (liver) makes things mol water soluble
introduces or unmasks polar groups (-OH, -NH2)
phase II detox = conjugation = add endogenous polar group to drug molecule
conjugators = glucuronic acid, sulfuric acid, acetic acid, amino acid
increased polarity allows for renal excretion

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