Meia-vida da Droga

t½ = 0,693/k.
Created by
Renato Passos, Eng. de Software
Reviewed by
Renato Passos, Eng. de Software

Last updated: Apr 18, 2026

6,93 h

Formula

t½ = ln2/k

About this calculator

The half-life of a drug is the time it takes for the concentration of a pharmaceutical to decrease by 50% due to metabolism and elimination. Calculating the half-life is essential in pharmacokinetics to understand how a drug behaves in the human body.

The formula to calculate the half-life is: t½ = ln(2)/k, where k is the elimination rate constant. This constant is measured in units of time, such as hours or minutes, and is specific to each drug.

The half-life is a critical parameter to determine the frequency of administration of a drug. For example, if a drug has a half-life of 6 hours, it needs to be administered every 6 hours to maintain the therapeutic concentration.

It's essential to remember that the half-life can vary from person to person and can be influenced by factors such as age, weight, health, and other medical conditions. Additionally, the half-life of a drug can change over time due to adaptation of the body or alteration of the drug concentration.

Frequently asked questions

What is the half-life of a drug?

The half-life is the time it takes for the concentration of a pharmaceutical to decrease by 50% due to metabolism and elimination.

Why is it important to calculate the half-life of a drug?

Calculating the half-life is essential in pharmacokinetics to understand how a drug behaves in the human body and determine the frequency of administration.

How is the half-life of a drug calculated?

The formula to calculate the half-life is: t½ = ln(2)/k, where k is the elimination rate constant.

Can the half-life of a drug vary from person to person?

Yes, the half-life can vary from person to person and can be influenced by factors such as age, weight, health, and other medical conditions.

What happens if the half-life of a drug changes over time?

The half-life of a drug can change over time due to adaptation of the body or alteration of the drug concentration.

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