During an evening shift on a medical unit, the only nurse on the unit is busy with an unstable client. The unit clerk, who is also both a certified medication aide and an unlicensed assistive personnel (UAP), reports to the nurse that a healthcare provider is on the telephone and wishes to prescribe an as needed (PRN) dose of an oral over-the-counter laxative for a client who is constipated. Which instruction should the nurse provide the unit clerk?