I use tretinoin cream to treat p&p. is there any tretinoin resistance if using it for longterm ? if so, can i still use it to stimulate skin turnover?

Some cautions below: You should avoid bright sun (use a sunscreen) and avoid multivitamins (which may increase the skin irritation by the drug). I can't find any reports of the medicine losing its effect over time. If irritation occurs, reduce the amount that you use.

P&P?: I am not sure what you mean by P&P. But triretinoin is great medicine and does not cause resistance. Some skin programs do recommend increasing the dosage for a week or two every 2-3 months but this varies. Ask your doctor for his opinion.