Common side effects of pentoxifylline include gastrointestinal discomfort, such as nausea, vomiting, and diarrhea. Some patients may also experience headaches, dizziness, or flushing. While these effects are usually mild, it is crucial for individuals to report any severe or persistent side effects to their healthcare provider. Rarely, pentoxifylline may lead to more serious complications, including changes in blood pressure or heart rhythm, necessitating immediate medical attention.