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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 position of equilibrium varies from base to base when a weak base reacts with water. The further to the left it is, the weaker the base. [5] When there is a hydrogen ion gradient between two sides of the biological membrane, the concentration of some weak bases are focused on only one side of the membrane. [6]
In the stomach, drugs that are weak acids (such as aspirin) will be present mainly in their non-ionic form, and weak bases will be in their ionic form. Since non-ionic species diffuse more readily through cell membranes, weak acids will have a higher absorption in the highly acidic stomach.
Glomerular filtration will only remove those drugs or metabolites that are not bound to proteins present in blood plasma (free fraction) and many other types of drugs (such as the organic acids) are actively secreted. In the proximal and distal convoluted tubules, non-ionised acids and weak bases are reabsorbed both actively and passively. Weak ...
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 ...
Like other opioids, fentanyl is a weak base that is highly lipid-soluble, protein-bound, and protonated at physiological pH. [71] All of these factors allow it to rapidly cross cellular membranes, contributing to its quick effect in the body and the central nervous system. [61] [119]
Amphetamine is a weak base with a pK a of 9.9; [20] 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. [20] [87] Conversely, an acidic pH means the drug is predominantly in a water-soluble cationic (salt) form, and less is ...
Amphetamine is a weak base with a pK a of 9.9; [186] 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.