Is 0.3mg Of Epinephrine Pen Safe For Child Weighing 45lbs?

My daughter usually has an epipen junior but they have all expired. Because our insurance doesn t pay for prescriptions, we asked her doctor to write a prescription for a generic epinephrine pen. After picking up her prescription, we noticed the dose is 0.3mg and the packaging says for 66lbs and up. My daughter weighs 45lbs. I called and the doctor told me 0.3mg for anyone 40lbs and up...but all the literature and information I can find online says otherwise. Are there new guidelines? Is 0.3mg okay for a 45lb six year old? This is strictly for a severe allergic reaction to tree nuts.