Vitamins for brain function - the need is understandable, but formulated a little incorrectly from the point of view of physiology. One could say simply - B vitamins for a month. And not a couple of vitamins and magnesium to them, as they sell in a pharmacy, but a solid complex.
Injecting is quite useless. Because no vitamins never enter the bloodstream directly. If you read that the B complex caused allergies, it is for that very reason. An unnatural way of entering the body!
The synthesis of these vitamins can, by the way, be adjusted by improving the intestinal microflora. Normal flora is able to maintain physiological values. Therefore, people with intestinal problems and have chronic fatigue, impaired memory and attention. It turns out that it is better not to decide on the forehead with the activation of the brain, but to see what lies at the heart of the violation.
There are natural substances - lecithin, omega-3 acids, coenzyme q10 - they quite significantly affect the assimilation of information ...
Of the safe "preparations" also natural, find AlfaMaxiel - affects the nutrition of nerve cells by improving microcirculation (this is a super pure extract from larch). Noticeable after 7 days,
Also - Biolan amino acids in capsules (just do not confuse it with powder). There, on reception, carefully: the capsule is not swallowed, but the powder is poured onto the tongue for quick absorption.
If you take imported, that is, Japanese peptide extract from asparagus, it has a strong protective effect on nerve cells. It is called Restartium Antistress.
But the reasons for the decrease in memory and attention still must not be forgotten: sleep on time, physical activity, nutrition and the state of microflora
Vitamins and / or nootropics are sheer nonsense. I tried different ones myself - no result. No result also because it cannot be measured. Nootropics are like homeopathy.
For your question, the solution is trivial - to maintain immunity, eat right, rest and give the body a moderate physical activity. Then the brain will be in order.
Try to drink phenotropil. It gives a very good result, which immediately becomes noticeable.
A really strong nootropic that justifies its price.