I am not familiar with Nicotinamide, and I have not located any information except advertisements promoting the product. I have developed a habit of being wary of promotional health supplements.

@mollyv, I commend you for discussing the use of Nicotinamide with your doctor.
@hello1234, Where did you read about it (Nicotinamide) as a prevention for skin cancer?

I did find this information for acitretin. Here is a link that includes usage, precautions, side effects, etc.
- Acitretin (Oral Route)
https://www.mayoclinic.org/drugs-supplements/acitretin-oral-route/description/drg-20061491