U2.3 DRG CONCENTRATION & RESPONSE : QDRC + DRG METABOLISM Flashcards
Graph of the fraction of a population that shows a specified response to increasing doses of a drug.
Quantal Dose Response Curve
Minimum dose required to produce a specific response is determined by each member of the population.
Quantal Dose Response Curve
Curve seen in a Quantal-Dose Response Curve
Sigmoid Curve
50% of the individuals/population manifested the
desired therapeutic effect.
ED50
Median effective dose
ED50
Median toxic dose
TD50
50% of the individuals manifested the toxic effects.
TD50
Median lethal dose
LD50
Ratio of the TD50 (or LD50) to the ED50 determined from the quantal dose-response curves.
Therapeutic Index
Represents an estimate of the drug safety.
Therapeutic Index
↑ Therapeutic Index = ___ Safety
↑ Safety
↑ Safety = ____ toxic dose, ______ effective dose
↑ toxic dose, ↓ effective dose
Dosage range between the minimum effective therapeutic concentration or dose (MEC) and the minimum toxic concentration or dose (MTC)
Therapeutic Window
More clinically relevant index of safety
Therapeutic Window
Maximal effect (Emax) an agonist can produce if the dose is taken to very high levels.
Maximal Efficacy
Determined mainly by the nature of receptors and their associated effectors.
Maximal Efficacy
Measured with a graded dose-response curve but not with the quantal dose-response curve.
Maximal Efficacy
Amount of drug needed to produce a given effect.
Potency
Curve used when the effect chosen is 50% of the maximal effect and the dose is (EC50)
Graded dose-response curve
Curve used when ED50, TD50, and LD50 are variables in 50% of the population.
Quantal dose-response curve
Variation of Drug Response
caused by differences in metabolism and immunologic mechanisms
Idiosyncratic Response
Variation of Drug Response
Response to the drug is unknown or unusual, and needs to be reported
Idiosyncratic Response
Variation of Drug Response
Intensity of the drug is decreased compared with the effect seen in normal reactions
Hyporeactive Response
Variation of Drug Response
Large dose of the drug is needed to have an effect
Hyporeactive Response
Variation of Drug Response
Intensity of the drug is increased or exaggerated compared
with the effect seen in normal reactions
Hyperreactive Response
Variation of Drug Response
Tolerance develops after a few doses
Tacyplaxis
Variation of Drug Response
Decreased sensitivity acquired as a result of frequent exposure (several doses) to the drug
Tolerance
Reason of Varied Drug Responsiveness
Decreases drug absorption, inhibits drug distribution, increases elimination of drug
Alteration in concentration of the drug
Reason of Varied Drug Responsiveness
variation occurs when foreign/exogenous ligands are introduced
Variation in the concentration of the endogenous ligands in antagonistic ptterns
Reason of Varied Drug Responsiveness
Down Regulation and Up Regulation
Alteration in number/function of receptors
Reason of Varied Drug Responsiveness
decrease in the number of receptors
Down Regulation
Reason of Varied Drug Responsiveness
increase in the number of receptors
Up Regulation
Reason of Varied Drug Responsiveness
When drug has been taken for a long time, then abruptly discontinued
Overshoot phenomenon/Rebound hypertension
Reason of Varied Drug Responsiveness
Propranolol
Overshoot phenomenon/Rebound hypertension
Reason of Varied Drug Responsiveness
cAMP, cGMP may lead to varied drug response
Changes in 2nd messengers
Reason of Varied Drug Responsiveness
Give the drug that really acts on the disease of the
patient
Clinical Sensitivity
T/F Drug causes a single effect only
False
T/F Drugs are selective but never specific
T
2 factors under Clinical Sensitivity in relation to their Beneficial and Toxic Effects
- Beneficial and Toxic Effects Mediated by the Same receptor-effector mechanism
- Beneficial and Toxic Effects mediated by Identical receptors in Different Tissue / Pathways
MORSE T/F Beneficial effects occur when the drug binds to the correct receptor on the intended tissue. Toxic effects occur when the drug binds to the same receptor on the wrong tissue.
Both T
How to avoid toxic effects
- Give low doses
- Carefully monitor the patient
- Employ ancillary procedures
- Use a safer drug
Low doses for prevention of blood clots, very high doses cause internal bleeding
Heparin
Give lowest dose possible, has anatomic selectivity
Steroids
Beneficial and toxic effects mediated by different types of receptors :
H1R - H1 blocker
H2R - H2 blocker
Antihistamine
Types of Drug Interactions
1+1 = 2
Additive
Types of Drug Interactions
Response elicited by combined drugs is equal to the combined response of individual drugs.
Additive
Types of Drug Interactions
Sedative (used for sleeping due to its effect by relaxing the brain) + ethanol (depressant)
Additive
Types of Drug Interactions
1+1=3
Synergistic
Types of Drug Interactions
Response elicited by combined drugs is greater than the combined responses of each individual.
Synergistic
Types of Drug Interactions
Penicillin G & Gentamicin
Synergistic
Types of Drug Interactions
0+1=2
Potentiation
Types of Drug Interactions
Drug which has no effect enhances the effect of the
second drug.
Potentiation
Types of Drug Interactions
Cimetidine + anticoagulant
Potentiation
Types of Drug Interactions
1+1=0
Antagonism
Types of Drug Interactions
Drug inhibits the effect of another drug.
Antagonism
Types of Drug Interactions
Heparin (anticoagulant) + protamine
(procoagulant)
Antagonism
