By Alesa Van Dyke

What is a Drug Half-Life?

A drug half-life is the approximate amount of time it takes your body to metabolize a specific drug. According to, “the half-life of a drug is an estimate of the period of time that it takes for the concentration or amount in the body of that drug to be reduced by exactly one half (50%)”.

For example, if 100mg of a drug with a half-life of 60 minutes is taken, the following is estimated:
• 60 minutes after administration, 50mg remains
• 120 minutes after administration, 25mg remains
• 180 minutes after administration, 12.5mg remains
• 240 minutes after administration, 6.25mg remains
• 300 minutes after administration, 3.125mg remains.

In theory, we can see that after 300 minutes, almost 97% of this drug is expected to have been eliminated. Most drugs are considered to have little effect after four-to-five half-lives. The actual half-life of a drug varies from person to person, because it depends on many variables.

Short Versus Long Half-Lives – Addiction Ramifications

Substances that have a shorter half-life tend to act very quickly, but their effects wear off rapidly. These drugs need to be taken several times a day to have the same effect, creating a tolerance, and leading to a higher chance of addiction.

Substances with a longer half-life may take longer to start working, but their effects persist for longer, and they may only need to be dosed once a day, once a week, or even once a month.

List of Common Substances and Their Half-Lives

Short Versus Long Half-Lives – Withdrawal and Recovery

When considering drugs with a high addiction or dependence potential, those with a short half-life are typically harder to withdraw from than those with a long half-life. For this reason, drug treatment programs often switch a person from a short-acting drug to a long-acting equivalent from the same class, in order to improve the withdrawal process.
• a short half-life = more withdrawal problems
• a long half-life = fewer withdrawal problems

Often, recovery starts by switching drugs, then tapering the dose. This switch helps people avoid the rush and the high, and the taper allows people to take smaller and smaller amounts of the drug, until they’re taking no drug at all. A tapering program can be difficult, but it might be the best way to ensure a long-term recovery.

A person reading this information may feel empowered to simply switch drugs and start tapering on their own, but we strongly advise against this. Many drugs cause very serious, painful withdrawal side effects. It is best to undergo a drug taper with the help of a medical professional. If you would like to know more, or need help with addiction, please call Aloha Behavioral Consultants at 801-399.1818.