Plasma Half-Life
Plasma Half-Life
Is time taken for drug concentration to fall to half of its initial value.
Types
Distribution Half-Life
Once the drug is administered in the body, initially there is a rapid fall in its plasma concentration due to its distribution in various body tissues.
The plasma half-life calculated for this distribution phase is called the distribution half-life.
Elimination Half-Life
Once the body tissues are saturated, the plasma concentration of the drug falls slowly due to elimination.
The plasma half-life calculated for this elimination phase is called elimination half-life.
If not specified, the term 'half-life' generally means the elimination half-life.
Plasma Half-Live in First order vs Zero Order kinetic
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rate of elimination is directly proportional to plasma concentration
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plasma half-life remains constant
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rate of elimination is not proportional to plasma concentration
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plasma half-life is not constant