Severe Side Effects Seek immediate medical attention if you experience any of these side effects, as they could be signs of pulmonary hypertension or heart valve disease. Shortness of breath (even with mild exertion or while laying down) Chest pain Fainting (or feeling like you might pass out) Edema (swelling in your ankles or feet) Pounding heartbeats or chest fluttering Confusion or irritability Unusual thoughts or behavior Feelings of extreme happiness or sadness Anxiety Seizures or partial-seizures Common Side Effects Nausea Vomiting Upset stomach Diarrhea Dry mouth Constipation Unpleasant taste in mouth Hives Impotence Palpitations or increased heart rate High blood pressure Hyperactivity Insomnia or sleep problems Restlessness Headache Tremors Dizziness Changes in sex drive