It is also sometimes called erythrocytosis, which means too many red blood cells. And it used to be called polycythaemia rubra vera or PCRV. PV is a type of rare blood disorder called a myeloproliferative neoplasm.These are conditions that cause an increase in the number of blood cells.t is also sometimes called erythrocytosis, which means too many red blood cells. And it used to be called polycythaemia rubra vera or PCRV. PV is a type of rare blood disorder called a myeloproliferative neoplasm.
Acetaminophen -- best known as Tylenol in the United States -- does not appear to help ease lower back pain and offers little relief for the most common form of arthritis, according to a new report.
  Tylenol Extra Strength contains just acetaminophen, an analgesic for pain and fever relief. Tylenol PM contains both the acetaminophen and diphenhydramine. Diphenhydrami â¦ ne is an antihistamine that is used as a sleep aid to help you get to sleep.ylenol is   just a brand name (McNeil Labs) â¦ for acetaminophen. Acetaminophen is acetaminophen, whether it's brand name is Tylenol, Datril, Panadol, Valorin, or approx. 60 other brand names. The same goes for aspirin.