Is it true that intoxicants remain in the stomach of their drinker for 45 days, and is there anything in Islamic law that supports this?

There are narrations indicating that the prayer of a wine-drinker is not accepted for forty days, among them the hadith narrated by Al-Tirmidhi from Abdullah ibn Omar, which is in Sahih Al-Jami'. The meaning of "non-acceptance" of prayer is the withholding of its reward, not that the prayer itself is invalid or that its obligation is dropped. Al-Manawi mentioned that the specification of forty days is due to the wine remaining in the stomach and veins for this period "mostly." This is based on worldly experience and knowledge, and its remaining does not affect the validity of the prayer, for the prayer is valid by the consensus of the people of knowledge.