Exactly as jayteeto says.
Carry a doctor's letter stating that your wife needs regular access to needles and medicinal liquids, and that it would be too risky for these to be hold-loaded in baggage which might be lost.
I'd also suggest carrying a few photocopies of the letter, and showing only a photocopy to security, as they might just want to keep it. If they keep the original, and you have no copies, you may encounter problems on your next flight.
Always tell security before the objects go through the scanner.
It makes your explanation more credible than one given after you've been "caught", and you'll find the scanner operators generally appreciate the fact that they've had advance notice from you that there is something coming through they should notice!
Best Regards
Bellerophon