The United States Food and Drug Administration (USFDA) approved the first drug for the psychosis linked to Parkinson's disease on Friday. The drug called Nuplazid, made by California-based Acadia Pharmaceuticals Inc, treats hallucinations that occur in 50 percent of the patients with Parkinson's disease. This is the first such approved treatment for the condition in the U.S.

An estimated 50,000 Americans are diagnosed with Parkinson's disease each year, according to the National Institutes of Health, and about one million Americans have the condition, an official statement said released on Friday said.

Parkinson's disease is a degenerative disorder of the central nervous system that eventually leads to loss in the movement of body and less ability to regulate emotions. 

It typically occurs in people over age 60 years when cells in the brain that produce a chemical called dopamine become impaired or die. Dopamine helps regulate the movements of the body.

The various symptoms of the disease include depression, hallucinations and delusions, difficulty in swallowing, chewing and speaking, urinary problems or constipation, skin problems and sleep disruptions.

The drug regulator has, however, asked Acadia Pharma to alert healthcare professionals prescribing Nuplazid drug with a black box on the label about an increased risk of death associated with its use to treat older people with dementia-related psychosis.

The USFDA said that the drug in its clinical trials showed common side effects such as swelling of the ankles, legs and feet due to the accumulation of excessive fluid in the tissue (peripheral edema), nausea and abnormal state of mind (confused state).

Nuplazid was also granted a breakthrough therapy designation for the treatment of hallucinations and delusions associated with Parkinson's disease.

Breakthrough therapy designation is a programme designed to expedite the development and review of drugs that are intended to treat a serious condition and where initial clinical evidence indicates that the drug may demonstrate substantial improvement over an available therapy.

The drug was also granted a priority review. The USFDA's priority review programme provides for an expedited review of drugs that offer a significant improvement in the safety or effectiveness for the treatment, prevention or diagnosis of a serious condition.