It doesn't have a strength on the bottle. It was mixed for her by a people pharmacy per my vet's instructions. It simply says give her 1/4 tablet every 8 hours - Tylenol #4. I know it is a high dose of codeine because he told me he was trying to minimize the amount of tylenol. It does say it can cause drowsiness and breathing problems, but she has been very agitated for the last 6 plus hours. Now she seem to be sleeping and snoring, but wakes with a start every few minutes and pants and then goes back to sleep.