Hmm I can't tell you for sure about inflammation- my body has inflammatory symptoms but never seems to show anything on related tests both before/after this med.
However, I have been on plaquenil 2 a day at 200mg for a few years now. It helped some with my autoimmune condition, but as I was on it before I developed ME/CFS I cannot say for sure if it has an effect on that. Depending on who your prescriber is- they may mis-prescribe the medication and give you too much or too little. Plaquenil has a specific ratio and from what I understand should not be given at doses higher than 400 a day. Some people do fine at 200 a day.
My gut instinct is - I'm pretty severe, and I don't think it is doing anything for the ME/CFS. I have no way to back that up other than what I'm experiencing on a daily basis.
Plaquenil has a "freaky rare side effect" involving the eyes, and requires 1-2 ophthalmologist visits and an additional visual field (done at a separate appointment) and eye scan a year (eye scan done at the visit). An ophthalmologist (eye specialist, often surgeons, and they also check you for glasses) may be harder to find than an optometrist (checks you for glasses) and many people confuse the two.
Do not confuse the two, unfortunately I know of someone who had the freaky rare side effect online and she is now blind because of this medication. Some people will tell you that does not happen, but unfortunately she was a 1 in a billion? type case. Due to the side effect almost always being reversible, that is why it is recommended you go before you start the med and go once a year thereafter.
Plaquenil helps my joint pain a little bit- apparently it is not incredibly effective for this. It helps most for the skin and mucousal involvement and protecting organs. They say it makes autoimmune diseases less likely to flare, and shortens the flares, but I have not found that to be true since it initially caused remission.
Many people get nausea and some other side effects from plaquenil.
For autoimmune diseases, plaquenil takes between 3 months and 1 year of consistent daily use to work.
Plaquenil is fairly expensive for many people. In my case I cannot take the generic due to allergy to a non-active component in the med. So I pay $50 a month with insurance. For comparison, my valcyte is about $10-20.
Without insurance, which I paid once, the med was over $200 for the name-brand. It is possible you will be fine with the generic. The generic is remarkably harder to swallow for me and caused more digestive pain/nausea/etc. To remedy, I took a pepcid before or after the med.
In my case I will be on it for life- unless my vision is damaged.
Plaquenil is not a pain killer on its own. It is an anti-malaria drug and what is called a DMARD or "disease modifying anti-rheumatic drug."
So it is possible it can calm inflammation if you are showing up with rheumatic inflammation markers in your blood- or any other values for rheumatic disease.
You might have trouble getting it prescribed.
The dose must be issued correctly.
It can be a long term commitment to know if it will help you.
It can be expensive.
If you need name brand it can be harder to get.
It has unusual eye related side effects that are not a joke- you must get your eyes checked even in the face of complacency (some doctors may tell you it is unnecessary until you have been on it for 3-5 years. That is a gamble I would personally not take.)