I should start by saying that my diagnosis is NMH (Neurally Mediated Hypotension), not POTS. However, at my last cardiologist visit he mentioned POTS when my heart rate went so much between the sitting/standing measurement. And since so much of this OI stuff overlaps, and the terminology is confusing, and I do take Florinef, I thought I'd add to the thread. I hope it is helpful and not confounding data!
I take Florinef as a part of a combination of medications. I take 1/2 tablet (0.05 mg) of Florinef first thing in the morning. I also take a prescription version of potassium, time released, 10 MeQ (Klor-Con). Finally, I take midodrine (ProAmatine), 5 mg, 4 times daily (about 3.5 hours apart, last pill taken 4 hours or more before bedtime). And I should not forget to add the extra salt (I take 5 salt tablets, Bio-Salt brand) and lots of water (about 3 liters daily).
This is the combination that I've been on for a few years now. I used to be on Florinef alone. Over the years I had ramped up to 1 1/2 tablets a day, taking 1/2 tablet (0.05 mg) three times a day. Florinef was helpful in several ways. One unexpected effect was that even though I was drinking more water (won't help much unless you increase salt and water intake) I was NOT waking up in the night to urinate. Previously I was getting up 1-2 times each night. So with the Florinef my body was holding in the fluids for a change.
However, over the years the effect started to wear off. That is why I kept increasing the dose. Then I tried Midodrine, and it works well for me, but the cardiologist suggested that a combination of both drugs might be best in my case. When I added the midodrine I cut down my dosage of Florinef. I also lost 6-7 pounds without trying. Florinef does seem to promote weight gain in some people.
One thing that's important to note is how differently people react to Florinef. For example, I get a lot fewer migraines since I've been on Florinef, not more. But the packet insert does mention headaches so I believe that it's a common side effect. It's wise to monitor any new drug and be wary of side effects, just in case.