1. A powder for use as a medicine, characterized in that it contains melatonin in an amount of from 35 to 90 wt.%, At least one water-soluble excipient in an amount of from 5 to 60 wt.% And at least one water-soluble surfactant in in an amount of from 0.5 to 5% of the total mass of the powder, said powder having an X90 of less than 100 microns and an average volume diameter of less than 50 microns. 2. A powder according to claim 1, characterized in that it contains particles in which melatonin, a water-soluble excipient and a water-soluble surfactant are present. A powder according to any one of the preceding claims, characterized in that it is obtained from a solution containing melatonin by spray drying. 4. A powder according to claim 1, characterized in that said water-soluble excipient is selected from the group consisting of: alitam, acesulfame potassium, aspartame, saccharin, saccharin sodium, sodium cyclamate, sucralose, trehalose, xylitol, citric acid, tartaric acid, cyclodextrin, dextrin , hydroxyethyl cellulose, gelatin, malic acid, maltitol, maltodextrin, maltose, polydextrose, sodium or potassium bicarbonate, sodium or potassium chloride, sodium or potassium citrate, phospholipids, lactose, sucrose, glucose, fructose, mannitol, sorbitol, natural amino acids, alanine, glycine, serine, cysteine, phenylalanine, thyroxine, tryptophan, histidine, methionine, threonine, valine, isoleucine, leucine, arginine, lysine, aspartic acid, glutamic acid, asparagine, glutamine, proline, their salts and any simple salts modifications, as in the case of N-acetylcysteine and carbocysteine, and mixtures thereof. 5. A powder according to claim 1, characterized in that said1. Порошок для применения в качестве лекарственного средства, отличающийся тем, что он содержит мелатонин в количестве от 35 до 90 мас.%, по меньшей мере один водорастворимый эксципиент в количестве от 5 до 60 мас.% и по меньшей мере один водорастворимый сурфактант в количестве от 0,5 до 5% от общей массы п
