Acetaminophen is a widely used and available OTC mild analgesic and fever reducer. It is known most commonly by the brand name Tylenol and is used in Ny-Quil and Day-Quil. Outside of the United States the drug also goes under the name Paracetamol.
It is commonly used for the relief of headaches, minor aches and pains, and as a method of reducing fevers. Acetaminophen is also known to have weak, but useful, anti-inflammatory properties.
 Side Effects and Drug Interactions
Acetaminophen has little to no side effects or interactions with drugs in small doses(up to 1,000mg). However, prolonged heavy use has been known to cause stomach bleeding. And acute doses can cause liver failure, especially if combined with alcohol.
Users consuming alcohol should limit their intake of acetaminophen, as the combination of the two strains the liver.
 Recreational Use
There is no significant recreational use for acetaminophen.
In fact, acetaminophen (or APAP as it is referred to when paired with more active drugs) is often included in prescription drugs that do have recreational uses as both a binder and abuse deterrent. The ratio of desired drug to APAP is often such that to take a feels-good dose of the primary compound you must also consume a liver punishing amount of Acetaminophen. This can be circumvented through the proper application of a cold water extraction.
If one must consume a large number of drugs containing acetaminophen, then try to keep it below the FDA approved limit of 4000mg per day. This will not do any significant damage to one's liver or other organs, granted it doesn't become a habit.