if Pka value is more for acidic drug,best side for absorption will be throughout the G.i.Tract.
pKa of drug can be determined from Handerson Hasselbatch equation., when conc. of salt become equal to acid i.e. at equivalence point when pH=pka then in H-H equn, pH=pka
Drug is available as ionised form and unionised for at particular pH. If unionsed drug concentartion is high at particular pH. The drug will be having better absorpation.
Doxofylline Pka value is about 9.8.
pKa = 15
It is around pKa=13
By following + or - 2 pH to the pKa value
To be honest, sometimes it can be extremely difficult to choose which equation you should use depending on whether the solution is basic or acidic. But what I do know, is that when the pka is small then the solution is acidic, and when the pka is large then the solution is basic. "A weak acid has a pKa value in the approximate range −2 to 12 in water. Acids with a pKa value of less than about −2 are said to be strong acids. " this being said, its hard to distinguish whether a solution is acidic or basic since they both have such a wide range of pka values. but if you want just a general guideline then i would stick with the rule "high pka=basic, low pka=acidic
The pka of a protonated ether (the conjugate acid) is about -3.5
To determine at which pH a drug will be 99.9% ionized, we need to consider the Henderson-Hasselbalch equation. The pH at which a drug is 99.9% ionized can be estimated by finding the pH value that is one unit above the pKa of the drug. Therefore, in this case, the drug will be 99.9% ionized at a pH of 6.
The conjugate acid is Hydrogen (H2), the pKa of which is 35.
3.3
7.6