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Pauling's second rule is that the value of the first pK a for acids of the formula XO m (OH) n depends primarily on the number of oxo groups m, and is approximately independent of the number of hydroxy groups n, and also of the central atom X. Approximate values of pK a are 8 for m = 0, 2 for m = 1, −3 for m = 2 and < −10 for m = 3. [28]
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-fold difference (due to log scale) between its pH and its pKa; therefore there is a 1000× difference between the charged and uncharged concentrations.
The estimated pKa values of hydrocortisone are 12.59 and -2.8 respectively. ... [15] [16] [18] They first identified cortisone to be one of the possible drugs, ...
Among the most common effects of this drug is increased blood cholesterol levels. ... Mycophenolate mofetil is reported to have a pKa values of 5.6 for the morpholino ...
In the case of multiple pK values they are designated by indices: pK 1, pK 2, pK 3 and so on. For amino acids, the pK 1 constant refers to its carboxyl (–COOH) group, pK 2 refers to its amino (–NH 2) group and the pK 3 is the pK value of its side chain.
Metformin has acid dissociation constant values (pK a) of 2.8 and 11.5, so it exists very largely as the hydrophilic cationic species at physiological pH values. The metformin pK a values make it a stronger base than most other basic medications with less than 0.01% nonionized in blood.
If a substance is present as several chemical species in the partition system due to association or dissociation, each species is assigned its own K ow value. A related value, D, does not distinguish between different species, only indicating the concentration ratio of the substance between the two phases. [citation needed]
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