Which of the following drugs has maximum chances of absorption from gastric mucosa?

* Diclofenac sodium is a weak acid and is non-ionized in the acidic medium of stomach. * Acidic drugs can cross the membranes in acidic medium. Therefore, it has the maximum chances of absorption from the stomach. * Other drugs given in the options are weakly basic drugs that are ionized at gastric pH. Note: Most of the drugs ending with 'INE' are basic in nature like morphine, quinidine, hyoscine, atropine, tubocurarine etc. Drugs forming salts with cations like sodium or potassium are acidic like diclofenac sodium, thiopentone sodium etc Drugs forming salts with anions like sulphate, phosphate etc are basic like morphine sulphate, chloroquine phosphate etc