Dose Response curve Dose Response curve Relationship between

Dose Response curve

Dose Response curve Relationship between amount of drug administered and response.

Types of Dose Response curve (DRC) v. Two types 1)Graded Dose-Response 2)Quantal Dose-Response

1) GRADED DOSE-RESPONSE v The response can be measured by unit of measurement v When dose of drug response also e. g. , contraction or relaxation of muscles, ∆ BP, ∆ blood sugar etc. v Studied in vitro on a piece of small intestine v Relationship b/w dose & response can be plotted on curve (x-axis=dose; y-axis=response) v Conc. /dose on log scale, curve is sigmoid-shaped (log dose-response curve)

Effect of various conc. of ACh on isolated small intestine of rabbit showing graded response

GRADED DOSE-RESPONSE CURVE

Advantages of log Dose-Response Curve § Wide range of drug doses is represented § Easy comparison between agonists § Easy study of antagonists § The middle portion (25 -75%) § of curve is linear; direct § relationship between dose and response can be obtained

GRADED DOSE-RESPONSE CURVE Following valuable data can be drawn Threshold dose: dose which produces first observed response ED 50/EC 50 (median effective dose or concentration): Dose or conc. which produces 50% of maximal response Cont.

• Drugs with same action at a receptor but with d/f potency show parallel DRC • Potencies of two drugs can be compared by ED 50 ED 100/EDmax (ceiling effect): Conc. which produces maximal response

2) QUANTAL DOSE-RESPONSE Ø The response can not be measured by unit of measurement Ø Response follow all or none phenomenon (e. g. , analgesics, convulsants, anticonvulsant activity, death etc) Ø Studied in whole animal (in vivo); data derived from group of animals or population

Ø Results can be plotted as Log dose-percentage curve Ø is obtained by keeping log doses on horizontalaxis and % response on vertical-axis