In Summary. Commonly reported side effects of pentoxifylline include: dizziness and nausea. Other side effects include: dyspepsia and vomiting. See below for a comprehensive list of adverse effects. For the Consumer. Applies to pentoxifylline: oral tablet extended release. Along with its needed effects, pentoxifylline may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention. Check with your doctor as soon as possible if any of the following side effects occur while taking pentoxifylline: