Michaelis menten constant (Km) =
[S] at 1/2 Vmax
Km relationship to affinity of enzyme for substrate
inverse - high affinity is low Km
Lineweaver-Burk plot - what does it show
reciprocal plot of Michaelis Menten curve (1/V vs 1/[S])
(non)competitive inhibitors - effects on efficacy vs potency
competitive dec potency
noncompetitive dec efficacy
volume of distribution eqn
= amt of drug in body / plasma drug conc
it is the amt of volume needed to contain the drug at the observed conc
how many half lives to reach steady state drug conc
4-5 half lives
eqn to calc half life
= 0.7 * Vd / Cl
Cl = clearance
eqns for loading and maintenance doses
loading = Cp x Vd/F maintenance = Cp x CL/F
F is bioavailability
3 drugs eliminated by zero order kinetics
phenytoin, ETOH, aspirin
PEA
phase 1 vs 2 of drug metabolism
1 - reduction, oxidation, hydrolysis by CYP450. Product still usually active. Geriatic pts lose this first
2 - conjugation (glucuronidation, acetylation, sulfation). product not usually active and ready to be excreted
G protein classes of SYNS, PSNS, DA, histamine, and vasopressin receptors
QISS and QIQ till you're SIQ of SQS alpha 1 - Q alpha 2 - I beta 1 - S beta 2 - S M1 - Q M2 - I M3 - Q D1 - S D2 - I H1 - Q H2 - S V1 - Q V2 - S
alpha 2 action
dec symp outflow
dec insulin release, lipolysis
inc platelet aggregation
M1 and M2 actions
M1 - CNS, enteric NS
M2 - dec HR and contractility
D1 vs D2 action
D1 - relax renal vascular smooth muscle
D2 - NT release, esp in brain
V1 vs V2 action
V1 - inc vascular smooth muscle contraction
V2 - ADH action in kidneys
bethanecol - mech use
direct cholinomimetic
used for ileus and urinary retention - bowel and bladder
carbachol - mech use
direct cholinomimetic
glaucoma, pupillary contraction, relief of IOP
pilocarpine - mech use
direct cholinomimetic
stimulates secrections, glaucoma
methacholine - mech use
direct cholinomimetic
challenge test for asthma dx
neostigmine - mech use
indirect cholinergic agonist
ileus, urinary retention, myasthenia gravis, reversal of NMJ blockades
pyridostigmine - mech use
indirect cholinergic agonist myasthenia gravis (long acting) - non CNS penetrating
edrophonium - mech use
indirect cholinergic agonist
dx of myasthenia gravis (very short acting)
physostigmine - mech use
indirect cholinergic agonist
anticholinergic toxicity - crosses BBB
donepezil - mech use
indirect cholinergic agonist
Alzheimer’s dz
cholinesterase inhibitor poisoning - sx and tx
DUMBBELSS
diarrhea, urination, miosis, bronchospasm, bradycardia, excitation of skeletal muscle & CNS, lacrimation, sweating, salivation
atropine + pralidoxime
atropine, homatropine, and tropicamide - mech, use
muscarinic antagonists
eye - mydriasis, cyclopegia
benztropine - mech use
muscarinic antagonist
Parkinson’s dz
ipratropium, tiotropium - mech use
muscarinic antagonist
COPD, asthma
oxybutynin - mech use
muscarinic antagonist
reduce urinary urgency and bladder spasms
glycopyrrolate - mech use
muscarinic antagonist
reduce airway secretions preop
receptors affected by epi, NE, and isoproterenol
epi - alpha 1, 2, beta 1, 2 (all strongly)
NE - alphas strongly, beta 1 weaker
isoproterenol - only betas
order that DA affects receptors based on inc dose
low dose - D1
med dose - add betas
high dose - add alphas
phenylephrine affects what receptors?
alphas
ritodrine - mech, use
beta 2 agonist
reduces premature uterine contractions
how do amphetamines and cocaine work?
both indirect sympathomimetics
amphetamines - releases stored catecholamines
cocaine - reuptake inhibitor
NE vs isoproterenol effects of BP / HR
NE - more alpha effect > vasoconstriction > inc MAP > reflex brady
isoproterenol - only beta effect > vasodilation > dec MAP > inc HR through reflex and beta 1
clonidine mech
alpha 2 agonist
phenoxybenzamine and phentolamine - mechs, uses
both alpha blockers, phenoxy is irreversible and phento is reversible
phenoxy - pheo
phento - MAO inhib pts who eat tyramine containing foods
-osin drugs - mech, use
alpha 1 blockers
HTN, BPH
tox of beta blockers
impotence, exacerbation of asthma, CV adverse effects - brady, AV block, CHF; CNS - seizures, sedation; use w/ caution in diabetics b/c dec insulin release
beta 1 selective beta blockers
A BEAM - acebutolol, betaxolol, esmolol, atenolol, metoprolol
partial beta agonist drugs
pindolol and acebutolol
drug causing gray baby syndrome
chloramphenicol
drugs causing hemolysis in G6PD def (6)
INH, sulfonamides, primaquine, aspirin, ibuprofen, nitrofurantoin
causes of drug induced lupus (4)
hydralazine, INH, procainamide, phenytoin
cinchonism caused by
quinidine, quinine
6 drugs causing seizures
INH, bupropion, imipenem, tramadol, enflurane, metoclopramide
-triptan class
5HT agonists for migraines
-zolam class
benzos (also -azepam)