more on plants 2

many plants have adaptations that provide chemical defenses to repel and even kill animals that feed on them.

plants sometimes store toxic compounds in hairs on the surface of their leaves, such as the stinging nettle.

many plants can be very useful as medicines.

in precise doses the 'poison' that plants create can be used to deter pathogens that threaten our health.

before a drug can be licensed it must undergo 5 stages.

the first is pre-clinical testing followed by 3 phases of clinical trials and finally after licensing trials.

animal studies and laboratory studies on iscolated cells assess safety and determine whether the compound is affective against the target disease during pre-clinical testing.

these trials determine whether the drug will be suitable for testing on humans. the trails are authorised by the medicines and healthcare products regulatory agency.

during clinical trials 1 and group of healthy volunteers are given different doses of the drug and the effects are reviewed by the MHRA.

during clinical trails 2 small groups of volunteers with the disease are tested to look at the drugs effectiveness. if the reuslts are promising the stage 3 clinical trials are set up.

during clinical trials 3 a large group of patients are randomly seperated into two groups. one group recieving the medicine and the other a placebo. the trail is a double blind randomized controlled trial.

if these results proove successful the drug will be licensed but will continue to be tested after licensing.