Fursultiamine is a synthetic derivative of thiamine (vitamin B1), developed to increase bioavailability and central nervous system penetration compared to standard thiamine. Thiamine plays an essential role in carbohydrate metabolism and neuronal function, and deficiency is well-known to cause neurological syndromes such as beriberi and Wernicke-Korsakoff syndrome. The rationale for using fursultiamine or thiamine to support or treat "nervous exhaustion" (a non-specific term that may refer to fatigue, stress, or neurasthenia) is based on the established importance of thiamine for proper nervous system functioning.

There is scientific evidence demonstrating that correcting thiamine deficiency can reverse neurological symptoms and improve mental and physical energy in deficient individuals. Fursultiamine, due to its improved absorption and CNS penetration, is used in Japan and some other countries for conditions associated with thiamine deficiency, including neuropathies and fatigue. However, high-quality clinical trials specifically investigating fursultiamine for "nervous exhaustion" in the absence of clear thiamine deficiency are limited. Some small studies and case reports suggest potential benefit in fatigue and mild cognitive symptoms, but systematic evidence is lacking.

In summary, the use of fursultiamine for nervous exhaustion is grounded in the scientific understanding of thiamine’s role in the nervous system and its proven benefit in deficiency states. However, direct evidence for its efficacy in otherwise healthy individuals with nervous exhaustion is weak, with scientific support rated at 2 out of 5.