Hi to_tired2009,
The medication is not dosed based on your age. The dose that one takes is based on their symptoms and severity of symptoms, and weight may be a factor. Just because you and your friend are the same age doesn't mean you should be taking medication the same way he does. If you and your friend both had high blood pressure, you wouldn't be expecting to take the same medication and dose as he does. You should be able to trust your doctor to give you the proper dose and treatment.
Casey