Plaquenil (hydroxychloroquine). When does it start to work? When will it be fully working n treating for rheumatoid arthritis? When will I notice improvement?

Takes time. Plaquenil (hydroxychloroquine) often takes at least 1-2 months for significant improvement with rheumatoid arthritis -- sometimes it can take up to 6 months for full effect. Be patient. If no improvement at all in 2-3 months though i would check with your doctor.
See details. It really takes 6-12 weeks to really gear up. That said, it is not my favorite for treating RA as the evidence that it is a true disease modifying agent is questionable. Often, low dose Prednisone is given at that same time to give immediately help until Plaquenil (hydroxychloroquine) hopefully works.