Relative Opioid Strengths
This page gives information on the generic and brand names of the major opioids along with the relative strengths of the drugs when administered intramuscularly and orally. Finally, the half-life of the drugs in the human body are given.
"Generic" is the generic name of the drug and "Brand" is the brand name of the drug. Often, a drug will be sold under more than one brand name; in this case, the most common brand name was selected. "IM" is the number of milligrams of the drug administered intramuscularly to be equivalent to 10 mg of morphine administered intramuscularly. "Oral" is the number of milligrams of the drug administered orally to be equivalent to 10 mg of morphine administered intramuscularly. "Half-life is the half-life of the drug, measured in hours. This information is taken from The Little Book of Opium.
- Heroin metabolizes to morphine very quickly--with a half-life of roughly 3 minutes. The half-life of morphine is reported.
- The most quoted figure for the half-life of Fentanyl is 2 hours. This seems to be taken from the Drug Information Handbook. I have seen numbers as low as 0.5 hours. The effective half-life of Fentanyl delivered through transdermal and transmucosal systems is roughly 7 hours.
- The 30 mg value is for the treatment of chronic pain, the 60 mg value is for the treatment of acute pain.