Class entries

This seems to be unique to Hong Kong, eg you will see phrases like this "Barbituric acid, its salts and its derivatives" in the drug lists and in the exam. Wonder what that means? This will enlighten you!
http://psdh.gov.hk/eps/eng/html/guide_to_class.pdf

Before I found this link off the Facebook Hong Kong Pharmacists site I used to spend ages pondering over what the derivatives of barbituric acid and other such drugs were, and would do what I usually do, resort to Google. I'd be looking at obscure chemical websites, a lot of them Indian based, copying down chemical structures in the vain hope that doing that might make it stick. So I'm pretty glad someone shared this info in the end, otherwise I honestly would have gone in to the exam none the wiser. Though they only ask one, maybe two questions with this structure per exam (What other drugs do they mean when they say 'barbituric acid, its salts and derivatives'?), so I probably would have survived.