A nurse is caring for a client who is taking diphenhydramine for insomnia and reports drowsiness. The nurse should identify that drowsiness indicates which of the following?

When a client who is taking diphenhydramine for insomnia reports drowsiness, this is an indication of an adverse reaction. Diphenhydramine is an antihistamine often used for its sedative effects to help with sleep, so experiencing drowsiness when taking this medication is an expected adverse effect. It is important for the nurse to assess and monitor the client for any other signs of adverse reactions and provide appropriate care as needed.