What is a side effect associated with the prolonged use of ibuprofen?

The prolonged use of ibuprofen is known to carry the risk of gastrointestinal bleeding, making it the correct choice. Ibuprofen, a nonsteroidal anti-inflammatory drug (NSAID), can irritate the stomach lining and lead to ulcers or bleeding when taken over an extended period or at high doses. This side effect is particularly significant in individuals who may have preexisting gastrointestinal conditions or those who are on other medications that also affect the stomach.

The other options do not accurately reflect side effects commonly associated with ibuprofen. Increased energy, for example, is not a typical reaction to an anti-inflammatory medication like ibuprofen. Instead, it is more often associated with stimulants. Similarly, while reduced appetite might occur in some cases, it is not a direct or commonly recognized side effect of ibuprofen use. Improved kidney function would be misleading, as ibuprofen may actually affect kidney function negatively, especially with chronic use. Hence, the risk of gastrointestinal bleeding stands out as a well-documented side effect of long-term ibuprofen use.