Can I change the drug overnight if both contain the same active substance - sertraline?

Asertin 50 mg is a drug that contains 50 mg of sertraline. If you received sertraline under a different trade name in the same dose, there are no contraindications to start using the substitute after finishing taking Asertin, especially since your entry shows that it is not possible to buy the drug under the current name. A drug of another brand with the same active ingredient may differ in the presence of excipients, but they are neutral, do not have their own effect and rarely - except for patients with a possible allergy - affect the tolerance of the product. You can read more about the replacements in the following article: https://www.gdziepolek.pl/artykuly/czym-sa-zamienniki-lekow