Inclusion Criteria:
* PAD as demonstrated by an ABI \<0 .9 in one leg or TBI less than \<0.7 in patients with an ABI \>1.3 (non compressible vessels)
* Rutherford Classification II, III
* Age \>18 years old
* Willingness to discontinue phosphodiesterase (PDE) 5 inhibitors such as Viagra, Cialis, Levitra, Revatio
* Willingness to discontinue phosphodiesterase (PDE) 3inhibitors cilostazol, milrinone or Vesnarinone
* Willing and able to comply with all study procedures
* Willing and able to provide informed consent
* Sexually active subjects willing to use an acceptable method of contraception while participating in the study
Exclusion Criteria:
* Hypotension defined as a systolic blood pressure less than 100mmhg systolic at screening or baseline visit
* Critical Leg Ischemia (Rutherford Classification IV, V, VI)
* Surgical intervention to alleviate symptoms of claudication in the study leg within the past 6 months or any endovascular interventions within 3 months or who is scheduled to undergo surgical revascularization in the next 6 month
* Walking limited by reasons other than claudication (e.g. arthritis, lung disease, severe neuropathy, lower extremity amputation except single digits)
* Serum creatinine \>1.5mg/dl or Hepatic enzymes \>2X the upper limit of normal
* Serum potassium greater than 5.0 or use of a potassium sparing diuretic at screening
* Pregnant, breast feeding or planning to become pregnant (subject or partner) at any time during the study.
* Myocardial Infarction, Cerebrovascular Accident or deep vein thrombosis within 12 months of screening
* Known history of nephrolithiasis
* History of ever having a seizure
* Concurrent disease or condition that would interfere with study participation or safety such as bleeding disorders, organ transplant, long term immunosuppression (excluding inhaled steroids), current neoplasm or severe gastroesophageal reflux
* History of vertigo or syncope within the past 10 years
* Enrollment in another drug or device study within 30 days of screening
* Required treatment with a drug known to inhibit folate metabolism (e.g. Methotrexate)
* Taking any of the following medications; PDE3 Inhibitors, PDE5 inhibitors, trental, nitrates, ginkgo biloba, levodopa, warfarin,
* Axillary lymph node dissection
* Presence of an amputation except single digits in either leg
* Preexisting illness that limits ambulation such as severe COPD, class III-IV heart failure, severe arthritis or back pain
* Glucose-6-dehydrogenase deficiency
