explain how the treatment of parkinsons disease overcomes the difficulty of drugs pas

Good morning!, how are u?

You probs know that there exists s-t called a blood-brain barrier, yeah? it prevents material passes from the blood to the rest of the body and vice versa [it is the main reason why brain tumours do not metastasize [spread] to other parts of the body] - it is s-t that has evolved to protect the [delicate] brain from toxins.

You will also have been taught [or this Q might state it prior] that there is a deficiency [shortage] of dopamine in some structures in the brain, in simple terms the basal ganglia, still ok?

If we give the patient a drug [it must be taken orally [by mouth][particularly as he/she will need it regularly, so injections are not feasible], it will reach all parts of the body [incl where not needed] and will likely cause unwanted side effects.

So, we give a drug like L-DOPA [L-dihydroxyphenylalanine [don't try to memorize the full name]], which crosses the blood-brain barrier and is then dehydroxylated [in simple lingo, broken down] to dopamine in the brain, where it is needed, yeah?

This dopamine then replenishes the patient's insufficient levels in the basal ganglia, hence helping him/her by relieving symptoms of Parkinson's disease somewhat - AHOY!!

Take care!