A team of Midland scientists are working on the world's biggest study into the drugs used to treat people with Parkinson's disease.

Researchers at Birmingham University have already begun their analysis of drug therapy for the condition.

Their work aims to determine which drugs provide the most effective control.

Through the trial, the team will look at the treatment of more than 850 British patients to determine which drugs offer the best control and fewest side effects, for both early and late Parkinson's.

There are four different types of drugs - levodopa, dopamine agonists, MAOB inhibitors and COMT inhibitors - and within each class, more than one drug is available.

Parkinson's is a degenerative neurological condition which often begins with a slight tremor in one hand, arm or leg and can affect both sides of the body, leading to problems eating, washing and other everyday activities. There is no known cure for it.

Levodopa improves the patient's muscle controls while dopamine agonists increase dopamine to the brain.

MAOB (monoamine oxidase type B) inhibitors reduce the breakdown of dopamine in the brain and COMT (catechol-O-methyltransferase) inhibitors reduce the brain's ability to breakdown levodopa.

Over a five-year period, university researchers will be closely monitoring patients and assessing their symptoms while they receive their normal drug therapy.

Although these drugs are known to work, no comparative studies have been done.

Patients with early Parkinson's are prescribed levodopa, dopamine agonists or MAOB inhibitors, while those with later Parkinson's who have motor complications that are uncontrolled by their existing drug therapy will be given one of the other drugs as follow-on treatment.

Dr Carl Clarke, the study's clinical co-ordinator at Birmingham University, said: "A real-life trial of this size should give us information to decide which make a real difference to people with Parkinson's disease."