UNIT 3 – PHARMACODYNAMICS Flashcards
It is the study of the effect of drugs on the body
PHARMACODYNAMICS
how avidly a drug binds its receptor or how the chemical forces that cause a substance to bind its receptor
DRUG AFFINITY
refers to the drug’s ability to activate the receptor once it has bound
to it
DRUG EFFICACY
facilitate receptor activation
Agonist
prevent receptor activation
Antagonist
the point at which increasing a drugs dosage no longer increases the desired therapeutic response
MAXIMAL EFFICACY
The concentration of drug in plasma that above these, toxic effects are precipitated.
MAXIMUM EFFECTIVE CONCENTRATION
refers to the amount of drug needed to elicit a specific physiologic response
or desired effect of a drug to produce a reaction. The maximal effect that a drug
produces irrespective of concentration or dose.
POTENCY
Both Drug A and Drug B achieve the same maximum effect
they have equal efficacy
has higher potency than Drug B
Drug A
achieves this effect at a lower dose
drug A
is more POTENT than Drug B
Drug A
describes the relationship between the therapeutic dose of a drug (ED50) and the toxic dose of a drug (TD50)
Therapeutic Index
the drug is moresafe to give
The higher the therapeutic index
TI =
TD50/ED50
Example: TD50 is 500 mg and ED50 is 250 mg = 500 / 250 = 2
need to be monitored closely for adverse effects.
Because the highest dose needed to produce a therapeutic effect is very close to the lethal or toxic dose.
Drug with lower therapeutic window
therepeutic Index
low therapeutic index
- lithium
- neuroleptics
- some antibiotics
- digoxin
- immunosuppressives
If a drug Therapeutic index is small
the drug is a narrow therapeutic index drug.
If a drug Therapeutic Index is big
the drug is a wide therapeutic index drug
therepeutic Index
High therapeutic index
- NSAIDs
- Sedative/hypnotics
- most antibiotics
- beta-blockers
High therapeutic index
NSAIDs
- aspirin
- tylenol
- ibuprofen
High therapeutic index
sedative/hypnotics
- benzodiazepines
low therapeutic index
neuroleptics
- phenytoin
- phenobartibal
low therapeutic index
some antibiotics
- gent/vanco/amikacin
PARAMETERS OF DRUG ACTIONS
- ONSET
- PEAK
- DURATION OF ACTION
PARAMETERS OF DRUG ACTIONS
Time from drug administration to first observable effect. The minimal effect of the drug is felt.
ONSET
PARAMETERS OF DRUG ACTIONS
ONSET formula is
T0 – T1
Example: A drug is given at 8AM (T0) and give the minimum effect at 8:15 AM
(T1), at 9AM (T2) the highest effectiveness of the drug was felt. At 10 AM (T3)
the drug was no longer felt.
PARAMETERS OF DRUG ACTIONS
PEAK formula is
T0 – T2
Example: A drug is given at 8AM (T0) and give the minimum effect at 8:15 AM
(T1), at 9AM (T2) the highest effectiveness of the drug was felt. At 10 AM (T3)
the drug was no longer felt.
PARAMETERS OF DRUG ACTIONS
DURATION OF ACTION formula is
Formula is T1 – T3
Example: A drug is given at 8AM (T0) and give the minimum effect at 8:15 AM
(T1), at 9AM (T2) the highest effectiveness of the drug was felt. At 10 AM (T3)
the drug was no longer felt.
PARAMETERS OF DRUG ACTIONS
Onset is 8am to 8:15 am =
15 minutes
PARAMETERS OF DRUG ACTIONS
Peak is from 8am to 9am =
1 hour
PARAMETERS OF DRUG ACTIONS
Duration of action is from 8:15 am to 10 am =
1 hour and 45 minutes
DRUG RESPONSE
- Primary
- Secondary
Example: Diphenhydramine (Benadryl)
DRUG RESPONSE
always desirable/physiologic effects
Primary
DRUG RESPONSE
desirable or undesirable
Secondary
DRUG RESPONSE
antihistamine; treat symptoms of allergy
Primary effect:
DRUG RESPONSE
dizziness, sleepy, drowsiness
Secondary effect
DRUG-DRUG INTERACTION
DRUG-DRUG INTERACTION
highest priority related to taking more than one
medication.
DRUG-DRUG INTERACTION
DRUG-DRUG INTERACTION
- Additive Effect
- Synergistic
- Potentiation
- Antagonistic
DRUG-DRUG INTERACTION
when two drugs given together have an effect equal to the sum
of their respective effects.
Additive Effect
DRUG-DRUG INTERACTION
drugs may increase each other’s effect to an amount that is greater than the sum of their individual effects. It increases the effectiveness of the drug.
Synergistic
DRUG-DRUG INTERACTION
the interaction of one drug increased by the presence of a second
drug.
Potentiation
DRUG-DRUG INTERACTION
The combined effect of two drugs is less than the sum of their individual effects. It decreases the effectiveness of the drug.
Antagonistic
Abnormal reactivity to the drug caused by a genetic
difference between the patient and normal individual. For example one patient taking
glutathione will result to healthy cells, whereas for patient with G6PD, glutathione will
cause anemia.
IDIOSYNCRATIC REACTION
The degree to which a drug can be poisonous and thus harmful to the human body. deleterious effects of drug over dosage or too much accumulation of drug
on the blood stream.
DRUG TOXICITY
