Vasodilators
Vasodilators
(estimated, untested doses)

Hydralazine:0.5 mg/kg twice daily.
Acepromazine:0.04-0.1 mg/kg twice daily.
Enalapril:0.25-0.5 mg/kg once daily

Nitroglycerine ointment, nitroprusside and ACE antagonists (very expensive) have unknown dosages and side-effects in horses.