| Date | May 2019 | Marks available | 1 | Reference code | 19M.3.sl.TZ1.17 |
| Level | SL | Paper | 3 | Time zone | TZ1 |
| Command term | Suggest | Question number | 17 | Adapted from | N/A |
Question
This question is about antiviral drugs.
Oseltamivir, used for the treatment of severe flu, is inactive until converted in the liver to its active carboxylate form.
Draw a circle around the functional group that can be converted to the carboxylate by hydrolysis.
Suggest a reason for using a phosphate salt of oseltamivir in oral tablets.
Anti-HIV drugs, such as zidovudine, often become less effective over time.
Explain the development of resistant virus strains in the presence of antiviral drugs.
Markscheme
[✔]
Note: Accept circles that include the alkyl side chain.
more soluble «in water» [✔]
viruses undergo «rapid» mutation [✔]
mutation causes a change in viral protein
OR
drug to no longer binds to virus [✔]
Note: Accept “rapid reproduction «allows resistant viruses to multiply»”.
Examiners report
Many students erroneously identified the amide as the required group, failing to realise that its hydrolysis would give the carboxylate ion of the side chain lost to the drug.
About a third of the candidates realised that producing a salt would increase the drug’s aqueous solubility, though many just stated “increased bioavailability” without explaining how this came about.
Another question where well argued responses were rare, though many students gained credit for mentioning the ease of mutation and the speed of reproduction of viruses.
Syllabus sections
- 17N.3.sl.TZ0.18b: State the method of drug administration that gives the maximum bioavailability.
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17M.3.sl.TZ2.15b.ii:
Compare, giving a reason, the bioavailability of soluble aspirin with aspirin.
-
20N.3.sl.TZ0.12:
Consider the following antacids:
Show that antacid X is more effective, per tablet, than antacid Y.
- 18N.3.sl.TZ0.12a: State the internal bond angles in the β-lactam ring and the expected bond angles for the same...
- 18N.3.sl.TZ0.13c: Outline the meaning of the bioavailability of a drug.
- 18N.3.hl.TZ0.17b: Outline the meaning of the bioavailability of a drug.
-
18M.3.sl.TZ2.15:
Drug testing is necessary to determine safe and effective doses.
Distinguish between the lethal dose (LD50) and the toxic dose (TD50).
-
19M.3.hl.TZ1.22b:
Suggest a reason for using a phosphate salt of oseltamivir in oral tablets.
-
17M.3.sl.TZ2.18b:
Suggest one ethical consideration faced by medical researchers when developing medications.
- 19N.3.hl.TZ0.21b: Experimental research on both animals and humans contributes to the development...
-
18M.3.sl.TZ1.13b.i:
State what is meant by the bioavailability of a drug.
-
19M.3.hl.TZ2.21a:
Distinguish between therapeutic window and therapeutic index in humans.
Therapeutic window:
Therapeutic index:
-
17N.3.sl.TZ0.18a:
Outline the difference between the therapeutic index in animal studies and the therapeutic index in humans.
-
17M.3.sl.TZ1.18a:
Dose response curves are determined for each drug.
Outline the significance of range “a”.
-
19M.3.sl.TZ2.14a:
Distinguish between therapeutic window and therapeutic index in humans.
Therapeutic window:
Therapeutic index:
-
20N.3.sl.TZ0.11d:
Comment on the risk of overdose when taking aspirin as an analgesic, referring to the following values, for a person weighing :
Minimum therapeutic dose
Estimated minimum lethal dose
-
20N.3.hl.TZ0.15d:
Comment on the risk of overdose when taking aspirin as an analgesic, referring to the following values, for a person weighing :
Minimum therapeutic dose
Estimated minimum lethal dose
