Aspirin is a mild analgesic derived from salicylic acid found in willow bark.

Describe how mild analgesics function.

The strong analgesics morphine and codeine are opiates. Outline how codeine can be synthesized from morphine. The structures of morphine and codeine are in section 37 of the data booklet.

Explain why opiates are addictive.

prevents/interferes with the production of prostaglandins

OR

prevents/interferes with the production of substances responsible for

inflammation/pain/fever

at the site of injury/source of pain

react with CH₃I/methyl iodide «in alkaline solution»

Accept “react with CH3Cl/methyl chloride” OR “react with methyl halide”.

Accept name or formula of a suitable specific methylating reagent (eg trimethylphenylammonium chloride etc.).

Accept “hydroxy/alcohol” but not “hydroxide” for “hydroxyl”.

Any two of:

interact with opioid receptors in the brain

alter the structure of brain cells

OR

alter the way the brain works «so that it only works normally when the opiates are present»

OR

prevents transmission of pain impulses inside the brain

release dopamine «that the person craves»

OR

give a feeling of pleasure/euphoria «that the person craves»

withdrawal symptoms «prevent patient from terminating drug use»

Accept specific withdrawal symptoms.

[Max 2 Marks]