Natrol 5-HTP (5-HTP) is a compound created in the body which is used to regulate serotonin levels in brain and central nervous system. 5-HTP be administered with a peripheral decarboxylase inhibitor (PDI) such as carbidopa in order to prevent 5-HTP's metabolism in the liver, which can lead to elevated levels of serotonin in the bloodstream. Research shows that co-administration with carbidopa greatly increases plasma 5-HTP levels. However, several studies have reported that 5-HTP is effective even without a PDI. Other studies have indicated the risk of a scleroderma-like condition resulting from the combination of 5-HTP and carbidopa. When Natrol 5-HTP was combined with the prescription Antidepressant, Anafranil, the most positive results were obtained. Natrol 5-HTP, which is found in infinitesimal amounts in certain foods like turkey and cheese, is often sold as therapeutic supplement. In this case, it is usually sourced from the seeds of Griffonia simplicifolia. Dose of 100mg of Natrol 5-HTP taken three times a day for an extended period of time showed a 50 % improvement in depressed patients. There are reports that indicate 50 mg of 5-HTP taken for six weeks has the ability to lower blood pressure especially when on a high carbohydrate. The only negative side effect was that there was an increase in Anxiety in almost half the patients in the study by Costa and Greengard (1984)."