Bioorganic and Medicinal 2018
Pharmacokinetics:
Pharmacokinetics
is defined as the study of the time taken for the drug absorption,
distribution, metabolism, and excretion. Clinical pharmacokinetics is the
application of pharmacokinetic principles to the safe and effective therapeutic
management of drugs in an individual patient. Primary achievements of clinical
pharmacokinetics include enhancing safety, efficacy, decreasing side effects,
Minimizing adverse effects and reducing toxicity of a patient’s drug therapy.
The development of strong correlations between drug concentrations and their
pharmacologic responses has enabled clinicians to apply pharmacokinetic
principles to actual patient situations.
Absorption
Absorption is the process of a
drug entering the blood circulation. Absorption depends on the route of
administration.
Distribution
Distribution is the drug's
dispersion through the body's fluids and tissues as it travels to its site of
action. This is dependent on blood flow, both to the area where the drug was
administered and throughout the body as well as protein binding.
Metabolism
Metabolism, or biotransformation,
is recognition by the body that the drug is present and the transformation of
the drug into usable parts.
Excretion
Excretion is removal of the drug
from the body. The primary site of excretion is the kidneys. Others include the
lungs, bile, saliva, sweat glands and skin.
Pharmacokinetics (PK)
refers to the study of:
1.How fast and how completely the drug is absorbed
into the body (from the stomach and intestines if it’s an oral drug)
2.How the drug becomes distributed through the
various body tissues and fluids, called body compartments (blood, muscle, fatty
tissue, cerebrospinal fluid, and so on)
3. To what extent the drug is metabolized
(chemically modified) by enzymes produced in the liver and other organs
4. How rapidly the drug is eliminated from the body
(usually via urine, faeces, and other routes)
Pharmacodynamics:
Pharmacodynamics is the study of physiological and biological
effect of drugs. The effect of a drug present at the site of achievement is
determined by that drug’s binding with a receptor.
Receptors may be present on neurons in the central nervous
system to depress pain sensation, on cardiac muscle to affect the intensity of
contraction, or even within bacteria to disruption of the bacterial cell wall.
Affinity, Efficacy,
& Potency
Affinity is
the attraction between a drug and its receptor. Efficacy is the drug's ability
to activate the receptor once it has bound to it. Some drugs have both a high
affinity and, while others have high one and low the other. Together, affinity
and efficacy affect potency, or the amount of a drug that's necessary to
produce a desired effect. The greater the affinity and efficacy, the greater
the potency.
Pharmacodynamics (PD)
refers to the study of:
It’s common during Phase I and II testing to collect blood samples at several
time points before and after dosing and analyse them to determine the plasma
levels of the drug at those times. Pharmacokinetic and Pharmacodynamic studies
are based on this information.
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