The last I looked in my 1st aid kit (that I rarely carry on the bike and usually resides in the car) various bandages, some micropore tape, scissors, and I think there may be a few plasters.
I do however always carry a spare jersey, and have quite a bit of gaffer tape wrapped around my pump.
Two key things I remember from my MBL and first aid instructors are, one, a mobile phone is the most important thing to carry. Getting help for serious injuries is far more important than treating them.
Two, the only wounds you’re interested in dealing with on the trail, are ones where big holes or lots of blood are involved. Anything that a plaster or antiseptic wipe will cure, can wait until you’re of the hill where you’ll have far better facilities to clean and dress it properly.
And for breakages, get creative. A jersey/inner tube/vet wrap/gaffer tape is far more useful than a triangular bandage will ever be.
As for drugs, my first aid instructor recommended carrying some aspirin in case you have to deal with somebody having a suspected heart attack, and possibly some ibuprofen for more general use.
The key things are, you should only ever offer the drugs, as you shouldn’t be telling people to take drugs, and if the person is likely to need surgery, they probably shouldn’t be taking drugs. However if you’re an hour or more away from help getting to you, some ibuprofen may help reduce pain a bit until some proper pain relief arrives. Just remember to tell the medics what they’ve taken.