Here's my current development with the RxNorm API http://screencast.com/t/VzUMdwP2b4H It's not too slow .. and we are only using it for searching for a drug. It may be a lot faster if you live on the American continent.
The good thing about the RxNorm database is that it is updated monthly. The bad thing is that it is a web service and is not as fast as using Synapse's database. So, we could cache the database call and periodically at night, run updates. There are 4 calls involved. Fetch all the drugs that match the spelling of a word Fetch all the drugs containing the drug found in step 1. Fetch all the details of that drug Fetch the ingredients of that drug.
Graham, I see the new e-prescribing page under Settings-->User-->E-prescribing that is set to work with SureScripts. Is any part of that working right now? Jerry