Is it possible to change the medicine to Hydroxyzinum Espefa 24 hours after taking 1 tablet of Ketilept?

Yes, you can do that. According to current medical literature, there should be no adverse interactions between these preparations that are harmful to health or the effects of drugs. Please remember that any modifications in the therapy should be made after consultation with the attending physician familiar with your state of health in detail. It is difficult for an outsider who has no knowledge on this subject to help and unambiguously establish an appropriate scheme of conduct. This is the competence of the doctor. A single intake of Ketrel does not allow you to observe the full effect of the drug. The effect should be visible after a few days to 2 weeks of use. Of great importance is the dose, ailments, concomitant diseases, as well as the predisposition of the body. I enclose additional information that may be helpful: https://www.gdziepolek.pl/artykuly/czy-przyjmowanie-kilku-lekow-jednoczesnie-jest-bezpieczne https://www.gdziepolek.pl/artykuly/czy-mozna-laczyc-leki-ze-soba