Common side effects include constipation, decreased interest in sexual intercourse, diarrhea, dry mouth, gas in the stomach, heartburn, Sexual dysfunction (ejaculation delay, inability to have or keep an erection, loss in sexual ability, desire, drive or performance), sleepiness or unusual drowsiness, trouble sleeping.
Less common side effects are bloated or full feeling, burning, crawling, itching, numbness, tingling feelings, chills, cough, decreased appetite, excess air or gas in the stomach, fever, increased sweating, joint pain, muscle aches and pains, pain in the neck or shoulders, passing gas, runny nose, sneezing, sore throat, stuffy nose, tightness of the chest, tooth problems, trouble breathing, unusual dreams, drowsiness & tiredness.