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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 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.
For substances that exhibit substantial plasma protein binding, clearance is generally dependent on the total concentration (free + protein-bound) and not the free concentration. [ 9 ] Most plasma substances have primarily their free concentrations regulated, which thus remains the same, so extensive protein binding increases total plasma ...
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 ...
The model outputs for a drug can be used in industry (for example, in calculating bioequivalence when designing generic drugs) or in the clinical application of pharmacokinetic concepts. Clinical pharmacokinetics provides many performance guidelines for effective and efficient use of drugs for human-health professionals and in veterinary medicine .
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.
A V D greater than the total volume of body water (approximately 42 liters in humans [5]) is possible, and would indicate that the drug is highly distributed into tissue. In other words, the volume of distribution is smaller in the drug staying in the plasma than that of a drug that is widely distributed in tissues. [6]
Alternatively, since the radioactive decay contributes to the "physical (i.e. radioactive)" half-life, while the metabolic elimination processes determines the "biological" half-life of the radionuclide, the two act as parallel paths for elimination of the radioactivity, the effective half-life could also be represented by the formula: [1] [2]