Question 19M.3.sl.TZ2.a
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.3.sl.TZ2.a |
| Level | sl | Paper | 3 | Time zone | TZ2 |
| Command term | Distinguish | Question number | a | Adapted from | N/A |
Medicines and drugs are tested for effectiveness and safety.
Distinguish between therapeutic window and therapeutic index in humans.
Therapeutic window:
Therapeutic index:
[2]
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.
Accept “difference between ED50/minimum effective/therapeutic dose «for 50% of population» AND TD50/toxic dose «for 50% of population»” for M1.
Do not accept reference to lethal dose used in therapeutic index in animal studies.
Most students receive one mark for this question and therapeutic window was probably the more successfully mark. Teachers need to remind students not to refer to lethal dose for therapeutic index. Some students forgot to mention the 50/50 % when explaining therapeutic index or inverted the ration as ED50/TD50.
