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.
Acetaminophen 500 mg is an active ingredient in Tylenol PM, according to Drugs.com. Acetaminophen acts to reduce fever and provide pain relief. This ingredient works by blocking prostaglandins, which are chemical signals that can cause fever and pain. However, Tylenol PM does not have anti-inflammatory effects like nonsteroidal anti-inflammatory drugs (aspirin, ibuprofen) do. According to Drugs.com, acetaminophen has no common side effects.