DP Chemistry (last assessment 2024)
Question 19M.3.hl.TZ2.21a
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.3.hl.TZ2.21a |
| Level | hl | Paper | 3 | Time zone | TZ2 |
| Command term | Distinguish | Question number | a | Adapted from | N/A |
a.
[Maximum mark: 2]
19M.3.hl.TZ2.21a
Medicines and drugs are tested for effectiveness and safety.
(a)
Distinguish between therapeutic window and therapeutic index in humans.
Therapeutic window:
Therapeutic index:
[2]
Markscheme
Therapeutic window:
range of dosage «over which a drug» provides the therapeutic/desired effect without causing adverse/toxic effects [✔]
Therapeutic index:
toxic dose of drug for 50 % of population divided by minimum effective dose for 50 % of population
OR
[✔]
Note: M1 may be scored from a correctly labelled diagram.
Do not accept reference to lethal dose used in therapeutic index in animal studies.
Examiners report
Most candidates receive one mark for this question, mainly for the therapeutic window. Some candidates inverted the ratio as ED50/TD50 for therapeutic index.
