Question

A drug is found to have following saturation solubilities at the room temperature (~25°C) pH S(umol/L) 7.4 205.0 10.0 9.0 10.0 5.5 12.0 5.0 Evaluate the nature of the drug as well as possible drug pKa and absorption of drug.

Answer 1

Criven drug has to be a weak base, because increase in ÞH (Incuase in conantation of oh") solubility of drug dicruas, Decrease in solubility is due to common on effect. Suppose BOH rubrusent wuak basic drug, which dissociate Partially as given BOH) = B+ (aq) + OH(aq) Addition of Strong base like NaOH or KOH NaOH - Na+ (aq) + OH- (aq) conanbration of oHº increase diu to addition of strong base NaOH, reaction procud in backward direction. TB+] [OH-] Ionic Product > Solubility product Pra of a drug suprisent the bH about which the drug is Soy. dissociated (Protonated) and 50%. (un protonated) undisociated. Since drug is weak bass in natur it's pka has to be the betwun 7 to 11. After swallowing the drug reachs the stomach where the acidic bH is maintained in lower part of stomach. Due to acid base neutralization bitaun basic drug and acid gastric juicy, the drug dissolve completely here.