Pharmacology Flashcards – First Aid for the USMLE STEP 1

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  • Km reflects the
    affinity of the enzyme for the substrate
  • Vmax is directly proportional
    to enzyme concentration
  • when you decrease Km you increase
    affinity
  • if you increase [S] what kind of inhibition can be overcome?
    competitive inhibition
  • competitive and noncompetitive inhibition effect on Vmax
    only decreases in noncompetitive inhibitors
  • competitive and noncompetitive inhibition effect on Km
    increased only in competitive inhibitors
  • what kind of inhibitor will decrease potency?
    competitive inhibitor
  • what kind of inhibitor will decrease efficacy?
    noncompetitive inhibitor
  • volume of distribution formula
    Vd = (amt of drug in body)/ (plasma drug conc)
  • low volume of distribution (4-8L) will distribute where
    in blood; these are the lg or charged molecules
  • medium volume of distribution will distribute where
    in extracellular space or body water; small hydrophilic molcules that do not bind plasma proteins
  • high volume of distribution (>body weight) distributes
    in all tissues; small lipophilic molecules that bind strongly to extravascular proteins
  • clearance
    rate of elimination of drug/ plasma drug concentration = Vd x Ke (elim constant)
  • how long does it take for a drug infused at a constant rate to reach steady state?
    4-5 half lives
  • half life equation
    (0.7 x Vd) / CL
  • loading dose
    Cp X Vd/F where F = bioavailability = 1; Cp = target plasma concentration
  • maintenance dose
    = Cp x CL/F
  • what happens to maintenance dose and loading dose in renal/liver disease?
    maintenance dose decreases and loading dose is unchanged
  • zero order elimination
    rate of elimination is constant regardless of Cp; constant amt of drug eliminated per unit time
  • examples of drugs that have zero order elimination
    "phenytoin, ethanol, aspirin (PEA)"
  • FIRST ORDER ELIMINATION
    RATE OF ELIMINATION IS Proportional to the durg concentration
  • "drug examples of weak acids, how do you treat overdose"
    "phenobarbital, methotrexate, aspirin; they are trapped in basic environments so treat overdose with bicarbonate"
  • drug examples of weak bases
    amphetamines; trapped in acidic environment so treat overdose with ammonium chloride
  • phase I metabolism
    "reduction, oxidation, hydrolysis; yields slightly polar, water soluble metabolites that are still active"
  • phase II metabolism
    "MN: GAS, old people have GAS bc they lose their phase 1 first; glucuronidation, acetylation,sulfation; yields very polar, INACTIVE metabolites"
  • efficacy
    "maximal effect a drug can produce; examples of high efficacy drugs are analgesics, abx, antihistamines and decongestants"
  • potency
    "amt of drug needed for a given effect; high potency drugs include chemotherapeutic, antihypertensive and antilipid drugs; examples are chemotherapeutic drugs, antihypertensive drugs and antilipid drugs"
  • competitsive antagonist
    "shifts curve to right --> decreases potency,"
  • noncompetitive antagonist
    shifts curve down --> decreases efficacy
  • partial agonist effect
    "acts at same site as full agonist, but with reduced efficacy; potency is variable"
  • physiologic antagonism
    substance that produces the opposite physiologic effect of an agonist but does not act at the same receptor
  • therapeutic index
    MN: TILE: TI = Ld50/ Ed50; safer drugs have higher TI
  • adrenal medulla and sweat glands
    "part of sympathetic NS but are innervated by CHOLINERGIC FIBERS (M receptor at sweat gland, N receptor at Adrenal medulla), both respond to Ach"
  • nicotinic Ach receptors
    ligand-gated Na+/K+ channels
  • muscarinic Ach receptors
    "G protein coupled receptos that act thru 2nd messengers ; 5 subtypes: M1, M2, M3, M4, and M5"
  • alpha 1 receptoer; q protein class
    "increases vascular smooth muscle contraction, increase pupil dilation, increases intestinal and bladder sphincter muscle contraction"
  • alpha 2 receptor; - I is the g protein class
    "decreases symp outflow, decreases insulin release"
  • "b1 receptor, s is the g protein class"
    "increases HR, contractility, renin release, lipolysis"
  • "b2 receptor, s is the g protein class"
    "vasodilation, bronchodilation , increase HR, contractility, lipolysis, increases insulin release, decreases uterine tone (relaxes bladder wall)"
  • "M1 receptor, q is the g protein class"
    "CNS, enteric nervous system"
  • "M2 receptor, I is the g protein class"
    decrease HR and contractility of atria
  • "M3 parasym receptor, q is the g protein class"
    "increases exocrine gland secretions, gut peristalsis, bladder contraction, bronchoconstriction, miosisis, ciliary muscle contraction (accomodation)"
  • "D1 recepter, s is the g protein class"
    relaxes renal vascular smooth muscle
  • d2 receptor; I is the g protein class
    modulates transmitter release esp in brain
  • "H1 receptor, q is the g protein class"
    "increases nasal and bronchial mucus production, contraction of bronchioles, pruritus, and pain"
  • "H2 receptor, s is the g protein class"
    increases gastric acid secretion
  • "V1 receptor, q is the g protein class"
    "increases vascular smooth muscle contraction,"
  • V2 receptor; s is the g protein class
    increase water permeability and reabsorption in the colelcting tubules of the kidney (V2 is found in the 2 kidneys)
  • Gq receptor pathway
    MN: Gq is CUTESY: Gq activates phosphoipase C which converts lipids to PIP2; PIP can become DAG (where it will activate PKC) or IP3 where it increases intracellular calcium
  • Gi/Gs receptor pathway
    inactivates/ activates adenylate cyclase which converts ATP to cAMP which then activates protein kinase A which can increase Calcum in the heart and increase myosin light chain kinase (smooth muscle);
  • what receptors have Gq and what receptors have Gi
    "MN: HAVe 1 M&M: H1, alpha 1, V1, M1, and M3 vs MAD2"
  • what receptors have Gs?
    "B1, B2, D1, H2, V2"
  • hemicholium
    "blocks reuptake of choline and wil shut down entire autonomic NS because it affects nicotinic receptors; will decrease BP by causing vasodilation, increase HR, decrease urinary output, induce ileus, GI motility decreases, mydriasis"
  • neuromuscular junction
    "nicotinic receptor that is a ligand gated Na+/K+ channel (Nm); when Ach binds, there is a conformational change that opens the channel and increases Na+ and K+ conductance thus causing depolarization"
  • curare
    competes with Ach for receptors on motor end plate; it is a nicotinic antagonist that works at the neuromuscular junction
  • metyrosine inhibits what
    conversion of tyrosine to dopa
  • reserpine inhibits what?
    CONVERSION Of dopamine to NE
  • guanethidine and amphetamine does what?
    guanethidine inhibits NE release and amphetamine stimulates NE release from the synapse
  • "cocaine, TCAs, and amphetamine does what at the noradrenergic receptor?"
    inhibits NE reuptake
  • Bethanechol
    activates Bowel and Bladder; direct cholinergic agonist; resistant to AchE
  • Carbachol
    "gluacoma, pupillary contraction, and relief of intraocular pressure; CARBon copy of ach"
  • Pilocarpine
    "potent stimulator of sweat, tears, saliva; contracts ciliary muscle of eye (open angle), pupillary sphincter (narrow angle); resistant to AchE; MN: you cry, drool and sweat on your PILOw"
  • Methacholine
    challenge test for dx of asthma; stimulates muscarinic receptors in airway when inhaled; direct cholinergic agonist
  • what are the 4 direct cholinergic agonists?
    "bethanechol, carbachol, pilocarpine and methacholine"
  • neostigmine is an anticholinesterase that is used to treat
    "urinary retention, myasthenia gravis, reversal of NMJ blockade; increases endogenous Ach; no CNS penetration; MN: NEO CNS: NO cns"
  • pyridostigmine
    "anticholinesterase; treats myasthenia gravis (long acting), does not penetrate CNS"
  • Edrophonium is used to diagnose what
    "myasthenia gravis bc it is short acting, increases endogenous Ach"
  • Physostigmine is an anticholinesterase used to treat
    glaucoma bc it crosses bbb and atropine overdose
  • echothiophate is an anticholinesterase that is used to treat
    glaucoma
  • cholinesterase inhibitor poisoning causes what kind of symptoms:
    "organophosphates irreversibly inhibit AchE; DUMBBELSS: diarrhea, urination, miosis, bronchospasm, brachycardia, excitation of skeletal muscle, and CNS; lacrimation, sweating, salivation"
  • antidote for cholinesterase inhibitor poisoning
    atropine + pralidoxime (regenerates active AchE)
  • examples of direct agonists (cholinomimetic agents)
    "bethanechol, carbachol, pilocarpine, methacholine"
  • examples of anticholinesterases (indirect agonists of cholinomimetic agents)
    "neostigmine, edrophonium, echotiophate, donepezil"
  • donepezil is used to treat
    alzheimer's disease; increases endogeneous Ach
  • atropine
    "muscarinic antagonist, produces mydriasis and cycloplegia for ophthalmic applications; treats bradycardia; blocks DUMBBELSS; decreases airway secretions, stomach acid secretion, gut motility, bladder urgency"
  • benztropine
    "muscarinic antagonist, treats PARKinson's disease; MN: PARK my BENZ"
  • scopolamine treats
    motion sickness; muscarinic antagonist
  • Ipratropium
    "muscarinic antagonist to treat asthma, COPD; MN: I PRAY I can breathe soon"
  • "oxybutynin, glycopyrrolate t"
    muscarinic antagonists used to treat urgency in mild cystitis and reduce bladder spasms
  • "methscopolamine, pirenzepine, propantheline"
    muscarinic antagonists used to treat peptic ulcers
  • toxicity of atropine
    "Increase body temp, rapid pulse, dry mouth, flushed skin, cycloplegia, constipation, disorientation; acute angle closure glaucoma in the old, urinary retnetion in men with prostatic hyperplasia and hyperthermia in infants"
  • epinephrine applications
    "anaphylaxis, glaucoma (open angle), asthma, hypotension (most effective at alpha1 and 2, and beta 1 and beta 2 receptors)"
  • norepinephrine applciations
    "hypotension (but decrease renal perfesion); most effective at alpha 1 and alpha 2 receptors, has some beta 1 effects"
  • isoproterenol applications
    "AV block (rare), most effective at beta receptors"
  • dopamine applications
    "shock (renal perfusion), heart failure; inotropic and chronotropic, D1 > B > A; effective at low doses on d1 receptors, medium dose for b1>b2 receptors, high dose to stimulate alpha 1 and alpha 2 receptors"
  • dobutamine applications
    "heart failure, cardiac stress testing, inotropic and less chronotropic; only effective at beta 1 receptors; cardiogenic shock"
  • phenyleprine applications
    "pupillary dilation without cycloplegia for ophthalmic procedures, vasoconstriction for hypotension, nasal decongestion for rhinitis; mainly an alpha 1 agonist; will increase BP via vasoconstriction but increased BP may elicit a reflex bradycardia"
  • terbutaline
    sympathomimetic drug that has the most effect on beta 2 receptors and is used for reduction of premature uterine contractions
  • examples of direct sympathomimetics
    "epinephrine, isoproterenol, dopamine, phenylephrine, ritodrine, albuterol"
  • to reduce premature uterine contractions
    "terbutaline, ritodrine"
  • metaproterenol and albuterol are used to treat
    acute asthma; both of which are sympathomimetics
  • examples of indirect symathomimetics
    amphetamine and ephedrine (both releases stored catecholamines); cocaine (uptake inhibitor of catecholamines)
  • what is amphetamine used for
    "indirect sympathomimetic; narcolepsy, obesity, ADD"
  • what is ephedrine used for?
    "indirect sympathomimetic, nasal decongestion, urinary incontinence, hypotension"
  • where are alpha 2 receptors found?
    "platelets (will cause aggregation), pancreas (will decrease insulin secretion); prejunctional nerve terminals (decreases transmitter release and NE synthesis)"
  • where are alpha 1 receptors found?
    "eyes (mydriasis), arterioles (contraction which increases afterload), veins (contraction which increases preload), bladder and sphincter (urinary retention), male sex organs (ejaculation), liver (increased glycogenolysis), kidney (decr renin release)"
  • where are beta 1 receptors found?
    "heart: SA , av NODES, atrial and ventricular muscle, His purkinje; kidney (will increase renin release)"
  • reflex bradycardia seen in what sympathomimetic?
    "norepinephrine bc it primarily affects alpha 1 and alpha 2 greater than beta 1; epinephrine at high doses because it affects alpha 1, beta 1 and beta 2"
  • epinephrine at different dosages
    "Epinephrine affects all the receptors (alphas and betas); at low doses, beta 1 will increase HR; beta 2 will decrease BP; at medium and high doses; beta 1 will still increase HR and beta 2 will decrease BP BUT alpha 1 will INCREASE BP;"
  • clonidine and alpha-methyldopa
    centrally acting alpha 2 agonists; treats HTN esp with renal disease (no decrease in blood flow to kidneys)
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