Half Life of Drug| Methods to determine Half Life| Biopharmaceutics| Pharmacokinetics| Made Easy

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The half-life of a drug is a pharmacokinetic parameter that is defined as "the time it takes for the concentration of the drug in the plasma or the total amount in the body to be reduced by 50%. In other words, after one half-life, the concentration of the drug in the body will be half of the initial dose.

In general, the effect of the drug is considered to have a negligible therapeutic effect after 4 half-lives, that is, when only 6.25% of the original dose remains in the body.

The formula for half-life is (t½ = 0.693 × Vd /CL)

Methods To Determine Half Life;
1_Graphical Method.
2_Non-Graphical Method.
* By Rate Constant (k)
* Volume of Distribution (Vd)
* Clearance (Cl)
* By Area Under The Curve (AUC)

The elimination half life is also a constant parameter for a drug and is independent of the administered dose and the route of drug administration if drug is eliminated by first order kinetics or by diffusion process.
Half life is increased by an increase in the volume of distribution and increased by a decrease in the rate of clearance.
In some disease states (eg. renal failure with edema) volume of distribution increases but clearance decreases, resulting in an unchanged half life (thus, it is a poor measure of drug clearance alone).

Chapters:
0:00 - intro
0:15 - Half Life of Drug
0:57 - Formula to Determine Half Life
01:42 - Example of Half Life
02:31 - Methods to Determine Half Life
02:46 - Graphical Method to Determine The Half Life
03:22 - Non-Graphical Method to Determine The Half Life
04:19 - Examples of Elimination Half Life of Various Drugs
04:53 - Clinical Importance of Half Life

Disclaimer:
"Content is For Education Purpose Only, Creamed From Various Authentic Books of Pharmacy & Medicine."
A Famous Quote is: "What We Know is a Drop. What We Don't Know is an Ocean".

[pharmacybyasim]

Here is a playlist of more video about Biopharmaceutics & Pharmacokinetics👇:

[polinastav]

1:32 shouldn’t clearance rate increase in this case? Otherwise half life won’t remain unchanged

[asimrph]

concisely explained about all aspects of half life !

[backlink]

very well explained.
please make a video about "AUC".
Thanks.

[kuddusjajira]

I dont understand if 15 minutes take to eliminates 50 mg then the next 15 minutes 25 mg why ? to eliminates 25 mg it should take less time isn't it ? Does half life constant?

[laxmansingh]

Half life is depend upon which property of molecules

[laxmansingh]

Half life is depend upon which property of molecules