"DRUG RESPONSE CURVE & THERAPEUTIC" it's a topic in which detail information about How Drug Response when taken in body & effect of various drugs on body with there Response Curve is Given.

1. DEPARTMENT OF PHARMACOLOGY
Subject : Pharmacology –I
Topic : Dose Response
Curve & Therapeutic

2. Dose Response Curve
Therapeutic index

3. DOSE RESPONSE CURVE
 ‘Dose’ is the amount of drug to administered to produce
a certain degree of response in a patient.
 Dose –response relationship has two components:
1.Dose-plasma concentration relationship
2.plasma concentration-response relationship
 Response : The change in activity of the cell or tissue
produce by the selected dose of the drug is
called the response .

4.  The dose and response is closely related to
each other and this relationship is called as
Dose response relationship.
 There is direct relationship between dose
intensity of response of the curve,
 i.e.the intensity of response increases with
the increase in dose.
 A typical curve showing the dose response
relationship is called dose response curve
(DRC).

5. Fig.1 : Dose response curve

6.  The DRC of drug is useful to predict potency,
efficacy & safety of drug.
1) Potency :
The position of DRC on the axis is an index of
drug potency. A DRC positioned rightward
indicates lower potency .Drug A is more potent
than drug B,since it produced intensity of
response as drug B as much smaller doses.The
relative potency is determined by comparing the
dose of two agonists at which they produces half
maximum response (EC50).
eg.10mg of Morphine is equivalent 100mg of
Pethidine to produce analgesia,hence morphine is
10 times more potent than pethidine.

7. Fig.2: log dose response curve for potency of drug A & B

8. 2) Efficacy:
The upper limit of DRC is the index of drug
efficacy & refers to the maximal response that can
be elicited by the drug ,eg .morphine produce a
degree of analgesia not obtain with any dose of
aspirin.
Morphine is more efficacious than aspirin.
Efficacy is a more decisive factor in the choice
of the drug.
Depending upon type of drug, both higher &
lower efficacious drug is cleanically prefered.

9. Fig.3:Log dose response curve for efficacy of drug A
& B

10. 3)Safety:
The slop of the upper part of the curve is useful
in assessing the relative safety of drug. eg. Most
CNS depressants have steep slope which indicates
a narrow margin of safety between the dose that
produces sedation & the dose that produces coma.
Dose individualization is required for use of such
drug to avoid toxic effect.
The drug with more shallow slope of curve
produces little increase in response over a wide
dose range & has greater margin of safety.

11. Fig.4: log dose response curve for safety of drug A &
drug B

12.  The gap between the therapeutic effect DRC &
the adverse effect DRC defines therapeutic index
of a drug.
 The therapeutic index gives a measure of safety
margin of a drug.
Median lethal dose
Therapeutic index=
Median effective dose
 Median effective dose (ED50) is the dose of a drug
necessary to half of all population & median lethal
dose is dose of a drug lethal to half of population.

13. Fig.5: Therapeutic index

14.  Therapeutic index is a range between the dose
which produces minimal therapeutic effect & the
dose which produces maximal acceptable adverse
effect.
Median toxic dose
Therapeutic index=
Median effective dose
 Therapeutic index is general index of the drug’s
safety & some patients may display extreme
sensitivity to certain drugs , eg. aspirin produces
severe hypersensitivity reaction in some patient at
the therapeutic doses.

15. 1) Medical Pharmacology,
K. D. Tripathi .
5th edition 2003,
Page no.46-48
2) Essentials of pharmacotherapeutics
F. S. K. Barar.
1st edition 1985,
page no. 32-34
3) Pharmacology
H.P. Rang & M.M. Dale ,
4th edition 2003
page no.11-12