Many products are only licensed for use by people of certain age groups or of specific genders. The instructions that come with such products often reflect the relevant licensing conditions. However doctors are allowed to prescribe unlicensed products and it should be perfectly safe to use anything prescribed (or simply suggested) in such a way.
For example, the leaflet that comes with women's HRT patches makes it very clear (probably unsurprisingly!) that they're not for use by men. However, despite being male, I'm using them right now as a result of having them prescribed for me by a consultant at Ipswich Hospital. (It's part of a trial for the treatment of prostate cancer).
Doctors know when it's safe to break the rules and when it isn't. For example, a teaching colleague of mine was taking Piriton anti-histamine tablets to treat his hay fever. He told his GP that the 'not to be exceeded' dose of just one tablet at night didn't really seem to be enough to ease his symptoms and that, if he was perfectly honest, he found the instruction to avoid mixing the tablets with alcohol somewhat irritating. The GP simply said "Blow what it says on the packet and just do what I do, which is to take four tablets every night with a very large whisky" ;-)
Trust your doctor. They don't kill that many people really ;-)