Question about half life of a drug

[Renald]

Question not about an exact drug, but merely about the pharmacological concept. Half life (T1/2) of a drug is the time needed for half the drug in the organism to be eliminated or the time needed for its blood concentration to decrease twice?

 

[dopemaster]

Why you just google the substance name and put half life in with your search?

Once you know the half life, then look up how half life works. I am not going to bother explaining something you can UTFSE for.

 

[thelung]

Half life: "the time required for any specified property (e.g., the concentration of a substance in the body) to decrease by half."

 

[aspiringchemist]

If the half life is 2 hours then in 2 hours 50% is excreted, in 4 hours 50% of the remaining 50% is excreted leaving 25%, in 8 hours 50% of the remaining 25% is excreted leaving 12.5% and so on...

 

[aspiringchemist]

After every elimination period, half of the remaining substance is excreted

 

[sekio]

half life is derived from blood concentration, usually

 

[Renald]

But blood concentration drop by 50% is not the same as the same drop in concentration (amount) in the body, as the organism is not one-compartment model. If you have a drug with a high Vd, halving the concentration in blood will not mean half the drug is eliminated from a body. This it the moment I dont understand.

 

[George27]

But blood concentration drop by 50% is not the same as the same drop in concentration (amount) in the body, as the organism is not one-compartment model. If you have a drug with a high Vd, halving the concentration in blood will not mean half the drug is eliminated from a body. This it the moment I dont understand.

You have found out because HL can be not so important.