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 intravenousy IV) 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 2 onssible pH range which could be used, also
bearing in mind any risks to the patient.