Effects of Tylenol

Tylenol (acetaminophen) is a unique medicine that reduces pain and fever, but has no anti-inflammatory activity. Acetaminophen relieves mild to moderate pain such as muscle pain, headache or pain associated with minor injuries. It is useful for reducing fevers associated with colds, flu and other minor infections. Many over-the-counter preparations of acetaminophen are available. It is also an ingredient in some prescription pain relievers. Acetaminophen is safe and effective for most people taking recommended doses, though it sometimes produces adverse effects as well.

Pain Relief

Acetaminophen works by inhibiting the production of prostaglandins in the brain and in nerve tissues. The body produces prostaglandins in response to injury or irritation. Prostaglandins induce nerves to send pain messages to the brain, which perceives the sensation. By blocking the production of prostaglandins, acetaminophen temporarily relieves pain. Acetaminophen is commonly used to treat the pain associated with headaches, dental problems, backaches, mild osteoarthritis, menstrual cramping and minor muscular injuries. Prescription medications with acetaminophen plus a narcotic pain reliever are used to treat moderate to severe pain.

Fever Reduction

Prostaglandins act on the temperature control center in the brain causing it to reset to a higher body temperature. By blocking the production of prostaglandins in the brain, acetaminophen interrupts their action on the temperature control center. The result is a temporary reduction in fever. Unlike aspirin, acetaminophen does not increase the risk of Reye's syndrome when used in children with viral illnesses.

Liver Toxicity in Overdose

Although prescribed dosages of acetaminophen do not damage the liver, severe liver injury may occur with overdose. The drug overwhelms the liver's capacity to metabolize it normally, and a secondary metabolic route produces a liver-toxic chemical. Mixing alcohol or other drugs with acetaminophen can augment the drug's liver toxicity. Liver failure requiring urgent liver transplantation may occur with acetaminophen overdose.

Kidney Toxicity in Overdose

Acetaminophen overdose may cause acute kidney failure. With recovery from the overdose, kidney function often returns to the level it was prior to the overdose.

Kidney Damage with Protracted Use

Protracted use of acetaminophen is associated with increased risk for acute and chronic kidney failure. Acute acetaminophen-related kidney failure is caused by a hypersensitivity reaction to the medication. Stopping the medication typically reverses the condition. Long-term ingestion of acetaminophen is associated with an increased risk of chronic renal failure. Stopping the medication usually halts disease progression.