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The charge of a molecule depends upon the pH of its solution. In an acidic medium, basic drugs are more charged and acidic drugs are less charged. The converse is true in a basic medium. For example, Naproxen is a non-steroidal anti-inflammatory drug that is a weak acid (its pKa value is 5.0). The gastric juice has a pH of 2.0. It is a three ...
The use of these models allows an understanding of the characteristics of a molecule, as well as how a particular drug will behave given information regarding some of its basic characteristics such as its acid dissociation constant (pKa), bioavailability and solubility, absorption capacity and distribution in the organism.
A drug's removal rate will be determined by the proportion of the drug that is removed from circulation by each organ once the drug has been delivered to the organ by the circulating blood supply. [1] This new concept builds on earlier ideas and it depends on a number of distinct factors: The drugs characteristics, including its pKa.
Physical properties of the drug (hydrophobicity, pKa, solubility) The drug formulation (immediate release, excipients used, manufacturing methods, modified release – delayed release, extended release, sustained release, etc.) Whether the formulation is administered in a fed or fasted state; Gastric emptying rate; Circadian differences
The drug coats and is absorbed through the mucous membranes ... Onset of absorption after oral ingestion is delayed because cocaine is a weak base with a pKa of 8. ...
Amphetamine is a weak base with a pK a of 9.9; [3] consequently, when the pH is basic, more of the drug is in its lipid soluble free base form, and more is absorbed through the lipid-rich cell membranes of the gut epithelium. [3] [29] Conversely, an acidic pH means the drug is predominantly in a water-soluble cationic (salt) form, and less is ...
In the context of pharmacokinetics (how the body absorbs, metabolizes, and excretes a drug), the distribution coefficient has a strong influence on ADME properties of the drug. Hence the hydrophobicity of a compound (as measured by its distribution coefficient) is a major determinant of how drug-like it is.
The dissociation constant is commonly used to describe the affinity between a ligand (such as a drug) and a protein; i.e., how tightly a ligand binds to a particular protein. Ligand–protein affinities are influenced by non-covalent intermolecular interactions between the two molecules such as hydrogen bonding , electrostatic interactions ...