Difference between nitroglycerine sublingual and tablets for anginal pain etc?

I have OI that has worsened. I have these new symptoms that starts with shortness of breath before I get this pressing heavy feeling in my left chest. Tried nitroglycerine sublingual spray a while back that seemed to be very helpful. Im now on the lookout for nitroglycerine sublingual spray but I have only found a source for tablets atm. Will ask my GP this week too.

Can I ask what your experiences has been with the different variants?

Found this:
Nitroglycerin (glyceryl trinitrate, CAS...

Difference between nitroglycerine sublingual and tablets for anginal pain etc?