The pharmacist is likely to warn Mrs. Kelly about drowsiness, a common side effect of diphenhydramine. It can impair alertness and should be considered when engaging in tasks requiring full attention. Awareness of this side effect helps ensure safe usage of the medication. ;
The chosen answer is C: Drowsiness. This is a well-known side effect of diphenhydramine, making it important for Mrs. Kelly to be aware of this effect as it may impair her ability to carry out tasks that require full attention.
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