Hi, Thanks for posting in HCM. I understand your concern. Promethazine belongs to a group of drugs called phenothiazines . It works by changing the actions of certain chemicals in the brain. It is used to treat allergy symptoms such as itching, runny nose, sneezing, itchy or watery eyes, hives and itchy skin rashes. It also prevents motion sickness. Some of the documented side effects include: 1. Tardive dyskinesia (effects due to Dopamine D2 receptor antagonism) 2. Confusion in the elderly 3. Drowsiness, dizziness and fatigue 4. Dry mouth 5. Constipation 6. Chest discomfort/pressure 7. Paresthesia 8. Short temper/irritability You need to seek medical attention promptly if any of the above side effects do not go away. It is not known to cause sexual dysfunction as the side effect. Hope the information provided would be helpful. All the best.