Nutrition labels tell us how many calories, carbohydrates and grams of fat and protein are in a serving, but few labels tell us how long the effect of a drug will last.
Taking a drug without knowing how and when your body will be affected -- and other pertinent informaton -- could be fatal.
Some drugs, such as the painkiller methadone, don't kick in right away, so anyone new to the drug is apt to take more and overdose.
Here is a list of drugs -- legal and illegal -- with their approximate half-life, which is the time it takes for the body to process half the drug.
For example, if you drink an 8-ounce cup of coffee, which contains 100 milligrams of caffeine, half of that amount will still be in your body about five hours later.
Note: The half-life times listed are approximations. They vary, depending on the strength of the drug and the dose, and on whether or not a tablet is slow- or immediate release.
Heroin: 30 minutes
Nicotine: 1 hour
Cocaine: 1 hour
Crystal methamphetamine: 1 hour
Acetaminophen (Tylenol): 2 hours
Morphine: 3 hours
Marijuana: 4 hours
OxyContin: 3 to 4.5 hours
Codeine: 4-6 hours
Coffee: 5 hours
Celecoxib (Celebrex): 11 hours
Methamphetamine: 12 hours
Methadone: 15-20 hours
Prozac: 7 days