I can't say for sure exactly how the liquid hydrocodone compares in strength to the tablets. That's something your pharmacist could tell you. However, I absolutely would not recommend giving a child of any age someone elses medication. It's both dangerous and illegal. Hydrocodone is a controlled narcotic drug. Your son's doctor should have prescribed him some pain medication following his surgery. If he didn't, please call his doctor and request a prescription. You can always tell him what you have on hand and ask if you could give him one of those. But please don't give either to him without his doctor's permission.