Sapropterin, also known as tetrahydrobiopterin, is a medication used primarily for the treatment of phenylketonuria (PKU), a genetic disorder that affects the body's ability to break down an amino acid called phenylalanine [1]. It is not typically used for cognitive improvement in individuals without PKU.

Regarding the side effects of using sapropterin, the available information indicates that it is generally well-tolerated [1]. Common side effects may include headache, nasopharyngitis, vomiting, and abdominal pain [1]. However, it is important to note that the use of sapropterin for cognitive improvement in individuals without PKU has not been extensively studied, and its safety and efficacy in this context are not well-established [2].

In conclusion, while sapropterin is considered safe and effective for the treatment of PKU, its use for cognitive improvement in individuals without PKU is not well-studied, and its safety and efficacy in this context are not well-established. Individuals considering the use of sapropterin for cognitive improvement should consult with a healthcare provider.

Sources:
[1] DrugPatentWatch. "Sapropterin Dihydrochloride (KUVAN) - Drug Patent Expiration and Generic Entry." DrugPatentWatch.com. <https://drugpatentwatch.com/drugs/sapropterin-dihydrochloride>.
[2] National Institute of Neurological Disorders and Stroke. "Cognitive Function." National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), 16 Nov. 2021, <https://www.ninds.nih.gov/health-information/disorders/cognitive-function>.