Pharm Unit 1 Flashcards
Pharmacokinetics definition
how the body handles the drug
Pharmacodynamics definition
effect of the drug on the body
ADME
absorption, distribution, metabolism, excretion
What is area under the curve
the actual exposure of the body to the drug after administration
what is Cmax
Maximum plasma drug concentration
What is Tmax
time at which Cmax occurs
How does solubility affect ADME
lipophillic vs. lipophobic (the more aqueous the drug, the faster it is absorbed)
what is partition coefficient
The ratio of a drug’s concentrations in oil phase vs aqueous
how does partition coefficient affect ADME
the higher the partition coefficient the more likely the drug will accumulate in fatty tissues
how does ionization affect ADME
charged molecules (ionized) do not cross membranes by diffusion
how does drug pKa affect ADME
the higher the pKa the slower it crosses
what is pKa
pKa is the pH where unionized = ionize
non-ionized: easily diffuse
ionized: do not diffuse
what is a prodrug
inactive precursors that are metabolized into active metabolites
benefits of a prodrug
increases drug aqueous solubility
higher aqueous solubility = higher drug concentration within body
higher aqueous solubility = more likely to remain in the blood
improve ADME
bioavailabilty definition
how much of drug is available to body after first/second pass metabolism
first pass metabolism
first pass = liver metabolism
low first pass drugs
IV drugs
high first pass drugs
calcium channel blockers, beta blockers, diuretics, lidocaine
how does a low first pas mean
bypasses liver- more bioavailability
what does F=1.0 mean
F = bioavailability
F = 1.0 means 100% bioavailability
or 100% of the administered drug was able to be utilized by the body for the targeted effect
where does Phase I and Phase II metabolism occur
- mostly liver
- gut
- kidneys
- lungs
- skin
Phase I
reduction
oxidation
hydrolysis
Phase II
glucuronidation
methylation
acetylation
what happens when a drug inhibits a CYP enzyme
prevents metabolism of drugs that are metabolized by the specific enzyme
concentration of drug increases
hepatic enzyme inhibition
decrease effect of metabolic enzyme
prevents activation of drug metabolism in liver
concentration of drug increases
hepatic enzyme inhibition outcome
metabolizes slower = more effective = need less drug
decreased elim rate = increased half life
hepatic enzyme induction
increase effect of metabolic enzyme
increases activation of drug metabolism in liver
expected concentration of drug is lower
hepatic enzyme induction outcome
slow onset
long duration
metabolizes faster = less effective = need more drug
increased elim rate = decreased half life
plasma protein binding
more bound a drug is = less active drug is
capacity
availability to bind
affinity
rate of binding
albumin characteristics
high capacity for binding
low affinity for binding
alpha 1 acid glycoprotein characteristics
low capacity to bind
high affinity for binding
therapeutic range/index definition
ratio of effective dose compared to lethal dose
good therapeutic index
wide
bad therapeutic index
narrow
first order kinetics
amount of drug eliminated is proportional to amount in body
drug that follows first order kinetics
epinephrine
ibuprofen
zofran
drug that follows zero order kinetics
alcohol
phenytoin
zero order connectics
amount of drug eliminated is fixed and independent of amount present in body
how to calculate loading dose
LD = (concentration x volume of distribution) / bioavailability (F)
when is half life predictable
if a drug follows first order kinetics
how to calculate half life
0.693/slope
what does half life mean for first order drugs
50% of drug is lost each half life
agonist definition
substance that mimics endogenous effect
antagonist definition
substance that blocks endogenous effect
partial agonist/antagonist
substance that has both agonist and antagonist properties
how does ED50 determine potency
lower ED50 = more potent
how to determine efficacy
higher the maximum point on curve
tolerance definition
occurs slowly over time and does not reverse rapidly after withdrawal of drug
Tachyphylaxis
occurs rapidly and reverses rapidly after withdrawal of drug
tolerance vs tachyphylaxis
tolerance = chronic
tachyphylaxis = acute
reversible/competitive action
drugs bind to receptor but can easily be kicked off by molecule with higher affinity
irreversible action
drug binds to receptor indefinitely
sedation definition
calming and drowsiness
hypnosis definition
produces drowsiness and facilitates deep sleep
anesthesia definition
global (reversible) CNS depression
what triggers MH
volatile anesthetics & succinylcholine
what happens in MH
mutation in RyR causes uncontrolled release of Ca2+ [IC] resulting in intense muscle contraction
MH key symptoms
extreme muscle metabolism
tachycardia
hypercarbia
hyperthermia
MH treatment
- hyperventilate
- give NaHCO3 (met. Acidosis)
- give insulin/furosemide
- give dantrolene (2.5mg/kg)
- cool pt
- treat other symptoms
barbiturates effects
*sedative
*hypnosis
*anticonvulsant
Barbiturates mechanism of action
increase duration of GABA Cl- chloride channel
barbiturate side effects
tissue damage
decrease BP / BF / ICP
increase HR
vasodilation
respiratory depression
hyperalgesia
histamine
Barbiturate drug interactions
precipitates w/ weak bases:
*Roc
* Lido
* Labetalol
* morphine
alcohol
benzos
opioids
Barbiturates Contraindications
elderly
anemic
shock
acute intermitent porphyria
barbiturate onset and duration
O= 10-20s (fast)
D = 8-20 min (short)
Barbiturate metabolism
CYP enzymes
barbiturate examples
phenobarbital
methohexital
benzos effect
sedation
anti-anxiety
hypnosis
muscle relaxation
anterograde amnesia
anticonvulsant
thrombophlebitis
benzos MOA
increases frequency of GABA Cl- channel opening
benzos side effects
pt may develop tolerance or dependance
benzos drug interactions
opioids: hypotension/resp depres
anesthetics: enhance potency
benzos onset
fast:
Midazolam < Diazepam < Lorazepam