Your question: I accidentally mixed two amps of albuterol and one amp of duoneb into my nebulizer. I didnt' realize what I did until I finished the treatment. Should I be worried?
My humble answer: You'll be fine. Albuterol and Duoneb are both safe medicines, even when doubled up like that. If it makes you feel any better, during my hardluck asthma days I went through an entire albuterol inhaler in a day, more than once. When patients are sick we often give back to back to back albuterol or duoneb or both treatments. They are much safer than older bronchodilators, and are very specific to the lungs. They also work great to end stubborn asthma attacks.
However, now that I admitted to all that... I have to say that if you need that much Ventolin your asthma is probably out of control and you should seek medical advice. Surely it's safe to double up on your meds once in a while, or by accident, but if it becomes a regular occurrence there's a greater problem going on.