Is it possible to "become immune" to Sotahexal? Why is the treatment not effective?

You should go to the attending physician and report the lack of noticeable effects of treatment. Treatment with Sotahexal starts with a low dose, which is then gradually increased until the patient's desired response is achieved. If the dose of 80 mg per day is ineffective, higher doses may be used, ranging from 160 mg to 320 mg per day in two divided doses. Dose escalation can only take place under medical supervision and should be preceded by appropriate tests, including ECG control, assessment of renal function and electrolyte balance. The body does not "immunize" itself to the drug. I attach a leaflet: https://www.gdziepolek.pl/produkty/73811/sotahexal-80-tabletki/ulotka