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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 take full effect. For this reason, drugs with a long half-life (e.g., amiodarone , elimination t 1 / 2 of about 58 days) are usually started with a loading dose to achieve their desired ...
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]
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.
Finally, using the Henderson-Hasselbalch equation, and knowing the drug's (pH at which there is an equilibrium between its ionized and non-ionized molecules), it is possible to calculate the non-ionized concentration of the drug and therefore the concentration that will be subject to absorption:
This is a list of abbreviations used in medical prescriptions, including hospital orders (the patient-directed part of which is referred to as sig codes).This list does not include abbreviations for pharmaceuticals or drug name suffixes such as CD, CR, ER, XT (See Time release technology § List of abbreviations for those).
It was proposed to be used instead of AUC in animal-to-human dose translation, as computer simulation shows that it could cope better with half-life and dosing schedule variations than AUC. This is an example of a PK/PD model , which combines pharmacokinetics and pharmacodynamics .
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]
Biological responses to ligand concentrations typically follow a sigmoidal function. The inflection point at which the increase in response with increasing ligand concentration begins to slow is the EC 50, which can be mathematically determined by derivation of the best-fit line.