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Levetiracetam, sold under the brand name Keppra among others, is a novel antiepileptic drug [7] used to treat epilepsy. [8] It is used for partial-onset , myoclonic , or tonic–clonic seizures, [ 7 ] and is taken either by mouth as an immediate or extended release formulation or by injection into a vein .
In clinical practice, this means that it takes 4 to 5 times the half-life for a drug's serum concentration to reach steady state after regular dosing is started, stopped, or the dose changed. So, for example, digoxin has a half-life (or t 1 / 2 ) of 24–36 h; this means that a change in the dose will take the best part of a week to ...
In pharmacology, clearance is a pharmacokinetic parameter representing the efficiency of drug elimination. This is the rate of elimination of a substance divided by its concentration. [ 1 ] The parameter also indicates the theoretical volume of plasma from which a substance would be completely removed per unit time.
A drug's characteristics make a clear distinction between tissues with high and low blood flow. Enzymatic saturation: When the dose of a drug whose elimination depends on biotransformation is increased above a certain threshold the enzymes responsible for its metabolism become saturated. The drug's plasma concentration will then increase ...
In this situation it is generally uncommon to talk about half-life in the first place, but sometimes people will describe the decay in terms of its "first half-life", "second half-life", etc., where the first half-life is defined as the time required for decay from the initial value to 50%, the second half-life is from 50% to 25%, and so on.
In pharmacokinetics, a loading dose is an initial higher dose of a drug that may be given at the beginning of a course of treatment before dropping down to a lower maintenance dose. [1] A loading dose is most useful for drugs that are eliminated from the body relatively slowly, i.e. have a long systemic half-life.
The plasma half-life or half life of elimination is the time required to eliminate 50% of the absorbed dose of a drug from an organism. Or put another way, the time that it takes for the plasma concentration to fall by half from its maximum levels.
t 1/2 is the half-life time of the drug, which is the time needed for the plasma drug concentration to drop to its half Therefore, the amount of drug present in the body at time t A t {\displaystyle A_{t}} is;