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31 Cards in this Set
- Front
- Back
Enzyme Kinetics
(Km, Vmax, types of inhibitors) |
- Km: [S] required to achieve 50% of Vmax; reflects the affinity of the enzyme for the substrate (low Km = high affinity)
- Vmax: velocity achieved as [S] approaches infinity (with constant [E]) - Competitive inhibitors: bind E thereby increasing Km (decreasing E-S affinity) - Noncompetitive inhibitors: bind ES thereby decreasing Vmax - Uncompetitive inhibitors: bind both E and ES thereby increasing Km and decreasing Vmax |
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Pharmacokinetics
(Vd, CL, t1/2) |
- Vd: volume of distribution = (amount of drug in the body)/(plasma drug concentration)
- Drugs with: low Vd distribute in blood; medium Vd distribute in extracellular space or body water; high Vd distribute in tissues - CL: (rate of drug elimination)/(plasma drug concentration) = Vd x Ke - t1/2: time required to change the amount of drug in the body by 1/2 during elimination (or infusion) - t1/2 = 0.7Vd/CL |
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Dosage Calculations
(Loading dose, Maintenance dose) |
- Loading dose = CpVd/F
- Maintenance dose = CpCL/F - Cp: target plasm concentration - F: bioavailability (= 1 when drug given IV) |
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Elimination of drugs
(0 order, 1st order) |
- Zero-order elimination: rate of elimination is constant (regardless of concentration); phenytoin, ethanol and aspirin are all zero-order at high/toxic concentrations
- First-order elimination: rate of elimination is proportional to drug concentration |
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Urine pH and drug elimination
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- ionized species get trapped
- weak acids: trapped in basic environments; treat overdose w/ biocarbonate - weak bases: trapped in acidic environment; treat overdose w/ ammonium chloride |
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Phase I vs. Phase II metabolism
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- Phase I: reduction, oxidation, hydrolysis (cytochrome-p450; usually yields slightly polar, water-soluble metabolites (often still active)
- Phase II: acetylation, glucuronidation, sulfation (conjugation); usually yields very polar, inactive metabolites (renally excreted) |
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Pharmacodynamics
(partial and full agonists) |
- a partial agonist has lower maximal efficacy than a full agonist
- potency is independent - efficacy: percent of maximal efficacy achieved by a given dose - potency: dose required to achieve a specific efficacy |
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Therapeutic index
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- TI = LD50/ED50 (TILE)
- LD50: median toxic dose - ED50: median effective dose - safer drugs have higher TI values |
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ACh Receptors
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- Nicotinic ACh receptors are ligand-gated Na/K channels
- Muscarinic ACh receptors are GPCRs that act through 2nd messangers |
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Bethanechol
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- direct cholinergic agonist
- used to treat postoperative and neurogenic ileus and urinary retention - activates bowel and bladder smooth muscle - resistant to AChE - Beth Anne, Call me if you want to active your Bowels and Bladder |
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Pilocarpine
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- direct cholinergic agonist
- potent stimulated of sweat, tears, saliva - contracts ciliary muscle of eye, pupillary sphincter - resistant to AChE - PILE on the sweat and tears |
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Neostigmine
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- indirect cholinergic agonist
- used for postoperative and neurogenic ileus and urinary retention, myasthenia gravis, reversal of NMJ blockade (postoperative) - increases endogenous ACh - no CNS penetration |
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Physostagmine
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- indirect cholinergic agonist
- used to treat glaucoma and atropine oversdoes - increases endogenous ACh - PHYS is for EYES (how shitty is that) |
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Cholinesterase inhibitor poisoning
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- syptoms include: diarrhea, urination, miosis, bronchospasm, bradycardia, excitation of skeletal muscle and CNS, lacrimation, sweating and salivation (also abdominal cramping)
- antidote: atropine (muscarinic antagonist) plus pralidoxime (chemical antagonist used to regenerate active cholinesterase) - DUMBBELSS |
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Atropine
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- muscarinic antagonist
- works on the eye - produces mydriasis and cycloplegia |
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Scopolamine
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- muscarinic antagonist
- works on CNS - used for motion sickness |
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Epinephrine
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- alpha-agonist
- decreases aqueous humor synthesis due to vasoconstriction - used to treat glaucoma |
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Atropine
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- muscarinic antagonist
- pupillary dilation, cycloplegia - decreased bronchial secretions - decreased stomach acid secretion - decreased gut motility - decreased bladder urgency in cystitis - blocks DUMBBELSS toxicity - increased body temp, rapid pulse, dry mouth, dry/flushed skin, cycloplegia, constipation, disorientation |
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Hexamethonium
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- nicotinic antagonist
- ganglionic blocker - used to prevent vagal reflex response to changes in blood pressure - toxicity: severe orthostatic hypotension, blurred vision, constipation, sexual dysfunction |
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Epinephrine
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- agonist of α1, α2, β1, β2, low doses selective for β1
- selective for beta-1 at low doses - used to treat anaphylaxis, open angle glaucoma, asthma, hypotension |
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Norepinephrine
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- agonist of α1, α2 > β1
- used to treat hypotension - but decreases renal perfusion |
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Isoproterenol
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- agonist of β1 = β2
- used as an AV block |
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Dopamine
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- agonist of D1 = D2 > β > α, inotropic and chronotropic
- used to treat shock (↑ renal perfusion), heart failure |
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Dobutamine
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- agonist of β1 > β2, inotropic but not chronotropic
- used to treat shock, heart failure and in cardiac stress testing |
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Phenylephrine
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- agonist of α1 > α2
- used to cause pupillary dilation, vasoconstriction, nasal decongestion |
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Terbutaline
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- agonist of β2 > β1
- used to reduce premature uterine contractions |
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Ritodrine
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- agonist of β2
- reduces premature uterine contractions |
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Ephedrine
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- indirect general sympathetic agonist; releases stored catecholamines
- used to treat narcolepsy, obesity, attention deficit disorder |
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Cocaine
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- indirect general sympathetic agonist; releases stored catecholamines
- causes nasal decongestion, urinary incontinence, hypotension |
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Clondine
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- centrally acting α2-agonist, ↓ central adrenergic outflow
- used to treat hypertension, especially with renal disease (no ↓ in blood flow to kidney) - are you sure this isnt an antagonist? |
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α-methyldopa
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- centrally acting α2-agonist, ↓ central adrenergic outflow
- used to treat hypertension, especially with renal disease (no ↓ in blood flow to kidney) - are you sure this isnt an antagonist? |