Dr. Drink Rum got a question for you

[md2002]

Drink Rum -

I'v been on this board for about 2 or 3 months and got some good info. I enjoy reading your posts because when it comes to scientific explanation you seem to know your sh*t.

Anyway, I am on Propecia and I keep hearing about half life and biological life. What do these mean. I have looked on the internet but it just confuses me more. I'd appreciate an explanation, if you have the time.

Thanks!!!

 

[drinkrum]

Elimination half-life is the time required for the amount of drug (or concentration) in the body to decrease by half. Drugs do not follow a linear pattern of elimination, so you simply can't multiply the half-life by two for the full elimination. Each substance has an individual elimination rate constant that can be defined as the fraction of drug that is eliminated per unit of time, e.g., fraction/h.

The formula for calculating half-life is: Half-life = 0.693/Ke, where Ke is the elimination rate constant. 0.693 is simply the natural log of 2, i.e. e^0.693 = 2 where e is Euler's number (2.71828...).

Why is this relevant for the layman? Drugs with shorter a half-life will be eliminated quicker by the system and may be considered safer since they impart less of an effect in units of time. Half-life however should not be confused with the duration of the drug's effects. For instance, the elimination half-life for finasteride is only 6-8 hours, but the effect of a single dose might last a few days. By contrast, the elimination half-life for dutasteride is 3-5 weeks, and I imagine its effects may persist for a few months.

D.

 

[md2002]

SO if I understand correctly, and I probably don't, 1mg of finasteride is out of my system in 6-8 hours but the drug will still be doing the job for a few more days ( biological life ). Sorry for being a layman I do appreciate the explanation!!

 

[drinkrum]

Yeah, something like that. That's why I recommend people who have side effects or whatever to stay off the drug at least a couple of weeks before jumping to any conclusions.

D.

 

[md2002]

Thanks for the info bro...