Phenytoin is an anti-epileptic drug. It is a weak acid with a pKa of 8.1 The unionised form is insoluble, and will form a precipitate. Consequently when infusing intravenously (IV) it is important to avoid this from happening.
A pharmacist prepares a phenytoin solution for IV infusion; commonly the pH of infusion solutions is pH 5.0 A colleague suggests they should consider changing the pH of the solution to avoid precipitation.
Using the Henderson-Hasselbalch equation, determine the best way for the pharmacists to proceed.