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A diagnosed case of rheumatoid arthritis on biological agent, still having pain needs to evaluated in detail. Pain can originate from muscle, nerves, or joints. The odd point is diarrhea for a month and it needs to be evaluated. It can be due to drug-related or disease-related diarrhea.
As per your information, you are having RA for the past four years. Your present complaint is excruciating pain in the upper and lower limb (duration is not mentioned). You tried painkillers, steroids, and antibiotics (the reason is not clear). Joint pain if related to RA usually responds well with painkillers like Etoricoxib, Naproxen, etc. If not fully then partially. It seems like your pain may be related to muscle origin or nerve-related which is very common in a patient with RA and hypothyroidism. You may have fibromyalgia, or nerve-compression symptoms which need to be evaluated by proper history and examination. It may be refractory RA. For chronic neuropathic pain or fibromyalgia pain, you can try Pregabalin and Duloxetine. And others after consultation and evaluation. Check the following-
1. ESR (erythrocyte sedimentation rate) and CRP (C-reactive protein) for RA-related pain.
2. LFT (liver function test), KFT (kidney function test), sugar (fasting), and thyroid profile for assessment of the origin of pain.
I hope this helps.