Parts of an Atom Like we said, atoms are made of three parts: protons, neutrons, and electrons. Those small parts are types of particles. And particles have properties, or features about them, that are important. One of those properties is mass, or how much stuff they contain.

The half-life of a drug is the time it takes for the amount of a drug’s active substance in your body to reduce by half. This depends on how the body processes and gets rid of the drug.

3 This means that if you begin taking a medication with a half-life of 24 hours, after four days, or on the fifth day, the rate of intake of the drug will approximately equal the rate of elimination. If the half-life is 12 hours, you’ll reach a steady state at the beginning of the third day (after 48 hours).

However, there are numerous other drugs with very long half-life, examples are mefloquine 14–41 days (25), amiodarone 21–78 days (26), and oritavancin 393 h (27). Furthermore, what can be called “long half-life” is always relative to the length of the sampling period.

Introduction. The duration of action of a drug is known as its half life. This is the period of time required for the concentration or amount of drug in the body to be reduced by one-half. We usually consider the half life of a drug in relation to the amount of the drug in plasma.

Half-life in the context of medical science typically refers to the elimination half-life. The definition of elimination half-life is the length of time required for the concentration of a particular substance (typically a drug) to decrease to half of its starting dose in the body.

Terminal half-life is the time required for the plasma concentration to fall by 50% during the terminal phase, and not the time required to eliminate half the administered dose.