Located a match to a white, round pill with 4171 above a cursive V, it's Meperidine 50 mg. Meperidine (commonly referred to as Demerol but also referred to as: isonipecaine; lidol; pethanol; piridosal; Algil; Alodan; Centralgin; Dispadol; Dolantin; Mialgin (in Romania); Petidin Dolargan (in Poland);[1] Dolestine; Dolosal; Dolsin; Mefedina) is a fast-acting opioid analgesic drug. In the United States and Canada, it is more commonly known as meperidine or by its brand name Demerol.