Stay hydrated
Compression socks
Exercise
Slow position changes
Review all meds that may contribute (blood pressure or prostate ones)
Sometimes we give salt tablets

Main meds that are trialed but rarely work:
- fludrocortisone
- midodrine
- beta blockers

Sometimes can capture the heart pausing with an implantable loop recorder in which case a pacemaker can help - but typically not so much in the positional component.

Honestly the best results are often with a dedicated exercise program but usually that benefit is for sedentary people, old people or teens that play video games all day.