Definitions

Question 1

Emax

Answer 1

Shows maximum response a drug can produce. Increasing the conc of drug produces no greater effect.

Question 2

EC₅₀

Answer 2

The Molar conc of a drug that produces 50% of the maximum response for that drug.

e.g. EC₉₀ shows 90% of max response.

It shows how potent drug is. Show conc needed to bring about effect. Low EC₅₀ then more potent the drug is as less of drug is required to produce maximum response.

Question 3

Potency

Answer 3

Describe the conc at which drug is effective. A potent drug is effective in very small amounts. Quantified using EC₅₀ so low value = more potent.

Question 4

Potency ratio (M)

Answer 4

Compare two drugs with same action so can calculate relative potencies.

M = EC_{50 (test)} / EC_{50 (standard)}

If you tested a drug for potency against standard drug and potency was less than 1 then the tested drug is more potent than strandard. If greater than 1 then drug tested is less potent than standard.

Question 5

Bioassay

Answer 5

Is any techniques where the potency of a drug is determined by measuring the biological response it produces.

Question 6

2+2 Bioassay

Answer 6

Middle bit of log conc-response curve is linear and may be parallel if two drugs are acting by same mechanism. Compare 2 doses of standard and two doses of unknown. Can calculate potency ratio between them.

Question 7

Therapeutic index

Answer 7

Ratio between toxic dose of a drug and dose producing desired therapeutic effects.

The higher the therapeutic index, the less chance of drug producing toxic side-effects in therapeutic use.

Therapeutic index = LD₅₀/ED₅₀

LD₅₀ = lethal dose in 50% of population

ED₅₀ = Effective dose in 50% of population

But this is no longer used as drugs have different ED₅₀ values deppending on disease that is treated. TD₅₀ in humas - toxic dose.