Morphine

• Extracted from the opium poppy (papaver somniferum), morphine is a powerful narcotic pain reliever. It is used primarily to treat moderate to severe pain, including the type of acute discomfort experienced after surgery. Morphine is most often administered intravenously in a hospital setting, although it is also available in oral medications.
  
  

Oxycodone

• Oxycodone is synthesized from codeine, which, like morphine, is a derivative of opium. It is used mostly as an oral medication, frequently in combination with aspirin, which is marketed as Percodan, or with acetaminophen, marketed as Percocet. Although it is usually administered orally, oxycodone can be given intravenously as well. It is sometimes preferred over morphine because it causes less depression of the respiratory system and causes less constipation. Like morphine, it is prescribed for the relief of moderate to severe pain.
  
  

Efficacy on Visceral Pain

• According to a study published in a 2007 issue of the "Scandinavian Journal of Gastroenterology," oxycodone outperformed morphine in the relief of visceral pain, which is pain that originates from one or more of the body's vital organs. The study, led by Danish pain researcher Dr. Lars Arendt-Nielsen, tested the comparative painkilling effectiveness of oxycodone, morphine and a placebo on 10 adults suffering severe pain from chronic pancreatitis.
  
  

Morphine Better on Back Pain

• An article in the July 2006 issue of "Formulary" reported on the findings of a back-pain study that were presented at the 25th annual scientific meeting of the American Pain Society, in San Antonio. That study compared the effectiveness of oxycodone and morphine in the relief of chronic low-back pain. It concluded that a once-daily dosage of extended-release morphine provided greater relief than twice-daily doses of controlled-release oxycodone.
  
  

Cancer Pain

• A systematic review of earlier trials on the comparative effectiveness of oxycodone and morphine in the relief of cancer-related pain showed that there was no significant difference between the two drugs. The findings, published in the April 24, 2006, issue of the "Archives of Internal Medicine," concluded that both the "efficacy and tolerability of oxycodone are similar to morphine, supporting its use as an opioid for cancer-related pain."