The common side effects of Tadalafil are: headache, indigestion, back pain, muscle aches, flushing, and a stuffy or runny nose. The potential side effects of Oxytocin are: nausea, vomiting. The potential side effects of PT-141 are: increased blood pressure, nausea, vomiting, skin flushing, stuffy nose, cough, tiredness, dizziness, or headache. For a full list of possible side effects see the important safety information.