Thank you for your interesting question. There are many sources of information about medication side effects:
1. The prescriber
2. The information leaflet with the medication
3. The internet
4. Word of mouth
Often, most prescribers will inform you of common side effects of medications and ones that they may have come across in clinical practice.
Sometimes, there are side effects that the prescriber and manufacturer are unaware of until they occur, this is despite clinical trials and rigorous testing of medications.
These then need to be fed back to the manufacturer and they add it to their information pack.
In this situation, it would be worthwhile if your friend spoke to the prescriber directly and discuss their concerns. Unfortunately, some sources on the internet are not regulated and hence are not always reliable.
BW
Dr Dinesh