A 2-year-old male presents with hyperactivity, fever, and sweating after 5 hours. What is his most likely accidental medication ingestion?

The symptoms described—hyperactivity, fever, and sweating—are highly consistent with the effects of pseudoephedrine, which is a common decongestant often found in over-the-counter cold and allergy medications. Pseudoephedrine stimulates the central nervous system, which can lead to increased alertness and hyperactivity, particularly in young children who may be more sensitive to its effects.

The onset of symptoms occurring after about five hours is also relevant since pseudoephedrine can have a duration of action that aligns with this time frame, especially if ingested in a significant enough quantity. These characteristics distinguish it from other medications listed.

Acetaminophen typically does not cause hyperactivity and is more associated with pain relief and fever reduction. Although it can cause fever if taken inappropriately, it does not produce the hyperactivity or sweating seen with pseudoephedrine.

Ibuprofen, while it can reduce fever and relieve pain, also does not typically present with hyperactivity as a side effect. Furthermore, the sweating associated with pseudoephedrine is largely due to its stimulant effects.

Diphenhydramine is an antihistamine that commonly causes sedation rather than hyperactivity and would not typically lead to the symptoms observed in this scenario.