Percodan
Percodan is a potent compound painkiller used to treat moderately severe to severe acute (short-term) pain.  Percodan contains aspirin and oxycodone, a potent opioid agonist.  Percodan was first marketed by DuPont Pharmaceuticals and prescribed in the United States in 1950.  At one time one of the most widely prescribed painkillers, Percodan has largely been replaced by alternative oxycodone compounds containing acetaminophen (Tylenol) instead of aspirin, such as Percocet.

# Pharmacology
Each Percodan tablet contains the following active ingredients:
- 4.5 mg of oxycodone hydrochloride
- 0.38 mg of oxycodone terephthalate
- 325 mg of aspirin.
Each tablet also contains the following inactive ingredients:
- FD&C Yellow 10
- FD&C Yellow 6
- microcrystalline cellulose
- starch.
The oxycodone component in Percodan is technically 14-hydroxy-7,8-dihydrocodein-6-one, a white odorless, crystalline powder which is synthesized from the opium alkaloid thebaine. Thebaine by itself has no therapeutic value. Oxycodone is metabolized into oxymorphone. Unlike morphine and like codeine, oxycodone has a good oral potency. Prior to the introduction of acetaminophen (paracetamol), Percodan was the mainstay in post-operative oral pain treatment due to the potency and long half-life of oxycodone. Percodan originally contained a small amount of caffeine.
The usual dose is one tablet every six hours as needed for pain.  The maximum daily dose should not exceed 12 tablets.

# Decline of use
Percodan has largely been replaced by Percocet (which is a compound of oxycodone and acetaminophen, instead of Percodan's aspirin) and other oxycodone-containing compounds for post-operative pain, since aspirin and other anti-inflammatory drugs increase prothrombin time and thus inhibit the blood from clotting, which can result in post-operative complications, such as excessive bleeding.  Norco and Vicodin, which contain hydrocodone and acetaminophen, have also gained favor over Percodan for post-operative pain because hydrocodone is nearly as potent as oxycodone, and it is not as highly regulated as Percodan.  In the United States, Percodan is regulated as a Schedule II controlled substance under the Uniform Controlled Substances Act of 1970, along with cocaine, morphine and raw (unprocessed) opium. Schedule II prescriptions may not be filled by telephone (except in an emergency), and no refills are allowed. By contrast, Vicodin, Norco, and other hydrocodone-containing compounds are in Schedule III.  Percodan is becoming something of a relic in the United States, at least, as the number of prescriptions has fallen precipitously since the 1960s in light of the alternate drugs available containing oxycodone (Percocet, Tylox, OxyContin, Roxicodone).

# Miscellaneous
Percodan is also sold under the brand name Endodan. All products containing oxycodone (including Percodan, Percocet, OxyContin) have the potential to be habit-forming. Oxycodone can produce drug dependence of the morphine type and, therefore, has the potential for being abused.  It is a favorite of and eagerly sought after by opiate addicts; many addicts, however, prefer OxyContin because it does not contain any other active ingredients besides oxycodone, unlike Percodan and Percocet, which each contain aspirin and Tylenol, respectively.
As of 2008, Percodan and Percocet are manufactured by Endo Pharmaceuticals.