I just started it 4 weeks ago at 0.25 mg. with my Integrative Long Covid Doctor. It's too soon to tell a difference and he wants me to work up to 0.50 mg.....i'm so sensitive to meds. Naltrexone is also given for thyroid & fibromyalgia. I tried it a few years ago for thyroid and was taken off due to some side effects that my primary at the time (he's retired now) thought was coming from the Naltrexone. My Long Covid Doctor thinks it was not the Naltrexone that caused the symptoms but the low B12 I was having. I am trusting the Lord and trying it again for Long Covid. I'll keep you posted.