Ivabradine for POTs

Today I had an appointment with my Cardio consultant at the local hospital.  At my previous three appointments he has asked me to try the drug Ivabradine to see if it would help my Postural Orthostatic tachycardia Syndrome (POTs).  I've been holding off, hoping that my heart rate would sort itself out as my other symptoms improve, but it hasn't really happened.  Anyway, yesterday morning, knowing I had the appointment today I took my first dose of Ivabradine.  I took it at about 6.30am and felt pretty rotten with a feeling of malaise and heaviness most of the morning.  Stairs were the worse with a horrible feeling of gravity pushing down on me as I climbed and very heavy legs.  In the afternoon I felt better and my heart did feel calm.  I put my heart rate monitor on for a couple of hours and my impression by the end of the afternoon was that there didn't seem to be much effect on my resting heart rate which was around 86 bpm whilst seated, but that it might be having some effect on my change to standing.  When I stood my heart rate was staying in the low 100's (up to 105), whereas some days standing can take it to 115 to low 120's.
I took a second dose at 7pm and felt horrible again but not for so long this time and when I took the third dose this morning again I felt horrid and heavy, but not for very long.
So I went along to todays appointment able to say that at last I had tried it.  My ECG heart rate on getting there was 105 bpm and my Doc didn't think the Ivabradine was really having any significant effect.  He suggested that I try it for a month - it is only day 2 after all - and when I'm a bit further in to the month he will do a 24 hour trace so we can get a picture of what's going on and whether it's helping.
Ivabradine is an angina drug and is not licensed for POTs, but some doctors have trialed it and had success with it for treating POTs - Article