Efficacy of Ambrisentan in Limited Scleroderma Patients in Improving Blood Flow to Hands or Feet

Subjects will receive ambrisentan 5 mg orally once daily or identical placebo pills for the first 4 weeks and then increased to ambrisentan 10mg once daily\[if the lower dose is tolerated\] or identical placebo pills for the rest of the study. They will be instructed to take the 5mg/pink pills for 4 weeks and then switch to 10mg /red pills unless they are having any drug related side effects or concerns. There will be no routine visit planned at 4 weeks to assess drug tolerance unless a complication arises. Adherence to treatment will be assessed by pill counting at each follow up visit. Follow up digital blood flow measurements will be obtained with LDPI at 1 week and at 3 months, where the same protocol (as that in the initial visit) will be followed.