Jessica Tagerman PharmD RPh Pharmacokinetics amp pharmacodynamics Pharmacodynamics What the drug does to the body Pharmacokinetics What the body does to the drug pharmacodynamics What the drug does to the body ID: 677321
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Slide1
Pharmacokinetics & pharmacodynamcs
Jessica Tagerman,
PharmD
,
RPhSlide2
Pharmacokinetics & pharmacodynamics
Pharmacodynamics: What the drug does to the body
Pharmacokinetics: What the body does to the drugSlide3
pharmacodynamics
“What the drug does to the body”Slide4
To best understand how drugs work, we are going to compare their mechanism of action to a “lock and key” model.Slide5
Unless you have the correct key, the lock won’t open!Slide6
An
endogenous
agonist is a natural substance produced by the body.The agonist
binds to a specific receptor, and causes some sort of physiological response in the body.Similar to the “lock and key” model, the agonist must fit perfectly into the receptor to cause activation.
Agonist moves towards and then binds to the receptor
Physiological Response
agonist
ReceptorSlide7
If the Molecule doesn’t fit perfectly into the receptor, the cell won’t activate and a physiological response will not occur.
(therefore, the molecule isn’t considered to be an agonist)
Agonist
No
Physiological Response
Receptor
Agonist
Molecule
Receptor
Agonist
Not a perfect fit, so this molecule will NOT activate the receptorSlide8
If the Molecule doesn’t fit perfectly into the receptor, the cell won’t activate and a physiological response will not occur.
(therefore, the molecule isn’t considered to be an agonist)
Agonist
Agonist
This molecule is only an agonist for…
THIS RECEPTOR!Slide9
Medications
Now, let’s talk about how medications relate to this model.
Drugs can be exogenous
agonists
, in which they mimic the endogenous agonist, bind to the receptor, and produce the pathological response.
Or, drugs can be antagonists, which block the receptor, and therefore prevent the endogenous agonist from binding and causing a physiological response (See next slide)Slide10
Antagonists:
Bind to the receptor in order to block the endogenous agonist from binding.
therefore, no physiological response will occur.
Agonist
Receptor
Agonist
Agonist
Antagonist
Agonist moves towards the receptor, but can’t bind, because the antagonist is blocking the receptor
Agonist
No Physiological ResponseSlide11
Summary
Agonists
BIND
to the receptor,
and
ACTIVATE
a cellular response
Antagonists
BIND
to the receptor, but
DO NOT
activate a cellular response
When you are studying the medications, understanding the physiological processes behind the diseases will help you understand treatment options!Slide12
Switching gearsSlide13
Pharmacokinetics
What the body does to the drugSlide14
Pharmacokinetics
Slide15
absorption
Absorption = Describes the process whereby a drug enters the circulatory system
Unless the drug is given via IV route, it needs to move from the site of administration into the bloodstream, so 100% of the drug may not be available as active medication (AKA, a drug’s BIOAVAILABILITY)
Oral Medications:
esophagus
stomach withstand stomach enzymes small bowel liver systemic circulationSlide16
Distribution
Distribution = The movement of the drug throughout the bloodstream and delivery to the site of action
Common sites of distribution: blood, muscles, fat tissue, organs
You need to be sure the drug is being delivered to where your body needs it!
(Remember carbidopa/levodopa? We needed the dopamine to be delivered directly to the brain, otherwise the medication wouldn’t work!)Slide17
Metabolism
Metabolism = when the drug is broken down or changed by various enzyme systems
Purpose of metabolism: mainly to begin elimination!
Drugs that have been metabolized = metabolites, may be active or inactive
Metabolites are formed with the help of enzymesSome drugs are inactive until they are metabolized to the active form that will cause the effect (These drugs AKA pro-drugs)
Some metabolites are responsible for the toxic side effects of medications.Slide18
Excretion
Excretion = how the drug and it’s metabolites are eliminated from the body
Routes of excretion depend on physiochemical properties of drug and function of excreting organ
Mainly excreted through urine and feces
Can also exit the body through exhalation and sweating, but to a lesser extentPatient with kidney failure: adjust medication dose, otherwise concentration of drug may increase to a toxic rangeSlide19
Half-life
Half-Life: Amount of time it takes for the blood concentration of a drug to decline to ½ of the initial value
Example: Medication with ½ life of 3 hours
Five times the half-life
is used to estimate how long it takes to essentially remove the drug from the body.
This would be 5 times the half-life of 3 hours, or 15 hours in the example above.
Time
Concentration
At 3
hrs
(max
concentration)
60 mcg/mL
At 6
hrs
30 mcg/mL
At 9 hours
15 mcg/mLSlide20
Blood concentration-time profiles
M
inimum
T
oxic
Concentration: Largest drug concentration beyond which there are toxic/undesirable effects
Minimum Effective Concentration:
Smallest drug concentration needed for effectSlide21
bioequivalence
Bioequivalence = drug products with same bioavailability
Pharmaceutical
Equivalents
Same active ingredient
(same salt form)
Same amount of active ingredient
Same dosage form
Inactive ingredients can be different
Pharmaceutical Alternatives
Same active ingredient
(but different salt form)
Amount of active ingredient can be different
Dosage form can be different
Inactive ingredients can be different
Therapeutic
Equivalents
Pharmaceutical
equivalents that produce the same effects in patientsSlide22
Questions?