Sulbutiamine is a precursor to thiamine (i.e., vitamin B1). As a dimer of two structurally modified thiamine residues, sulbutiamine retains many of the features of thiamine. However, the thiazole rings are open, the alcohol groups are esterified, and a disulfide bridge connects the two thiamine analogues. Sulbutiamine is indicated for the treatment of asthenia. Its ability to reduce fatigue is also considered desirable by athletes, and it is available for over-the-counter sale as a nutritional supplement. In one study of chronic fatigue patients, sulbutiamine did not demonstrate sustained benefits over the placebo, which raises doubts about its clinical efficacy. However, the authors of that study suggest that additional research is needed to evalulate the potential usefulness of sulbutiamine in the treatment of chronic fatigue. Sulbutiamine may be beneficial for cognition. Indeed, the demonstrated ability of sulbutiamine to improve memory in rats and patients of schizophrenia suggests that it is a nootropic. Recent research also shows support for the use of sulbutiamine in the treatment of erectile dysfunction. Sulbutiamine may reduce fatigue, memory difficulties, and intellectual tiredness; it may also speed convalescence.