Monday, July 19, 2010

Physical properties of drug affect pharmacological activities of drug

Do physical properties of a drug affect pharmacological activities of that drug ?
The physical properties of a drug do affect the pharmacological activity; Physical properties are secondary properties of any drug, which are resultant of the chemical properties of that drug.

For example solubility of any of drug depends up on the chemical structure, rather its constituent atoms and bonding impart intramolecular hydrogen bonding and polarity, atom and bonding polarity in turn decides spacial orientation of that drug molecule and crystal characteristics and solubility. Spacial orientation we all study in stereochemistry, or orientation of drug molecule, is important as it may hinder or enhance the approach and attachment of a drug molecule to its receptor.

The drug molecule acts on a particular site (receptor) when it reaches that point, and this we call as availability of that drug at the point of action, we call it as bioavailability.

Physical properties of a drug molecule are very important in achieving solubility in the biological medium , if the drug is very much soluble in water it is bound to be excreted faster and the point of actions which it may act will be restricted to the tissues which are abundant of fluids , and if a drug is lipid soluble it is more likely that it will get absorbed in to the fatty tissues more rapidly like nervous system and brain , and tissues with high lipid content , thus the abortion of such drugs is faster in such tissues action is faster on such tissues , example of such drugs are tricyclic anti depressant which they have a common tricyclic rings which impart lipid solubility.

Both properties have their own advantages and disadvantages, one will not facilitate quicker absorption while other enhance absorption and excretion and so the half life of the blood concentration.
Physiological activity is some thing we can say the consequences of attachment of a drug molecule to its receptor, these may be

1. Inhibition
Example: Enzyme Inhibition (Competitive or complete)

2. Activation, or agonistic action
Drug can act as if it is a part of our body’s biochemical process or reactions there by there by bringing about a desired biochemical reaction which may help our body to maintain normal biochemical activities.

3. Synergistic action, drug may enhance the ability of the particular enzyme of hormone or protein to produce more activity.

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