Question: how long does it take night nurse to kick in?
Answer: How long does it take to work? Promethazine will start to make you feel sleepy around 20 minutes after you take it and may work for up to 12 hours. If you're taking it for a cough or cold, allergies or nausea, your symptoms should start to improve within 20 minutes. The medicine should work for around 4 to 6 hours.