Information:  - Sodium oxalate, or disodium oxalate, is the sodium salt of oxalic acid with the formula NaCO. It is usually a white, crystalline, odorless powder, that decomposes at 250270 °C.  - Oxalate (IUPAC: ethanedioate) is the dianion with the formula , also written . Either name is often used for derivatives, such as salts of oxalic acid, for example sodium oxalate NaCO, or dimethyl oxalate ((CH)CO). Oxalate also forms coordination compounds where it is sometimes abbreviated as ox.  - A symptom (from Greek , "accident, misfortune, that which befalls", from , "I befall", from - "together, with" and , "I fall") is a departure from normal function or feeling which is noticed by a patient, reflecting the presence of an unusual state, or of a disease. A symptom is subjective, observed by the patient, and cannot be measured directly, whereas a sign is objectively observable by others. For example, paresthesia is a symptom (only the person experiencing it can directly observe their own tingling feeling), whereas erythema is a sign (anyone can confirm that the skin is redder than usual). Symptoms and signs are often nonspecific, but often combinations of them are at least suggestive of certain diagnoses, helping to narrow down what may be wrong. In other cases they are specific even to the point of being pathognomonic.  - Intermittent claudication (Latin: "claudicatio intermittens") is a symptom that describes muscle pain (ache, cramp, numbness or sense of fatigue), classically in the calf muscle, which occurs during exercise, such as walking, and is relieved by a short period of rest. It is classically associated with early-stage peripheral artery disease, and can progress to critical limb ischemia unless treated or risk factors are modified.  - Oxalic acid is an organic compound with the formula CHO. It is a colorless crystalline solid that forms a colorless solution in water. Its condensed formula is HOOCCOOH, reflecting its classification as the simplest dicarboxylic acid. Its acid strength is much greater than that of acetic acid. Oxalic acid is a reducing agent and its conjugate base, known as oxalate, is a chelating agent for metal cations. Typically, oxalic acid occurs as the dihydrate with the formula CHO·2HO. Excessive ingestion of oxalic acid or prolonged skin contact can be dangerous.  - Naftidrofuryl ( INN , also known as nafronyl or as the oxalate salt naftidrofuryl oxalate or nafronyl oxalate ) is a drug used in the management of peripheral and cerebral vascular disorders as a vasodilator . It is also claimed to enhance cellular oxidative capacity , and may also be a 5 - HT2 receptor antagonist . It is also licensed for the treatment of intermittent claudication due to peripheral arterial disease . Naftidrofuryl is marketed under the trade names Artocoron ; Azunaftil ; Di - Actane ; Dusodril ; Enelbin ; Frilix ; Gevatran ; Iridus ; Iridux ; Luctor ; Nafti ; Naftoling ; Naftodril ; Nafoxal ; Praxilene ; Sodipryl retard ; Vascuprax . Historically , it has been used to treat sudden idiopathic hearing loss and acute tinnitus . Naftidrofuryl may be effective for relieving the pain of muscle cramps .  - Dimethyl oxalate is a chemical compound from the group of oxalates (specifically, the dimethyl ester of oxalic acid).  - Peripheral artery disease (PAD) is a narrowing of the arteries other than those that supply the heart or the brain. When narrowing occurs in the heart it is called coronary artery disease while in the brain it is called cerebrovascular disease. Peripheral artery disease most commonly affects the legs, but other arteries may also be involved. The classic symptom is leg pain when walking which resolves with rest, known as intermittent claudication. Other symptoms including skin ulcers, bluish skin, cold skin, or poor nail and hair growth may occur in the affected leg. Complications may include an infection or tissue death which may require amputation; coronary artery disease, or stroke. Up to 50% of cases of PAD are without symptoms. The main risk factor is cigarette smoking. Other risk factors include diabetes, high blood pressure, and high blood cholesterol. The underlying mechanism is usually atherosclerosis. Other causes include artery spasm. PAD is typically diagnosed by finding an ankle-brachial index (ABI) less than 0.90, which is the systolic blood pressure at the ankle divided by the systolic blood pressure of the arm. Duplex ultrasonography and angiography may also be used. Angiography is more accurate and allows for treatment at the same time; however, it is associated with greater risks. It is unclear if screening for disease is useful as it has not been properly studied. In those with intermittent claudication from PAD, stopping smoking and supervised exercise therapy improves outcomes. Medications, including statins, ACE inhibitors, and cilostazol also may help. Aspirin does not appear to help those with mild disease but is usually recommended in those with more significant disease. Anticoagulants such as warfarin are not typically of benefit. Procedures used to treat the disease include bypass grafting, angioplasty, and atherectomy. In 2010 about 202 million people had PAD worldwide. In the developed world it affects about 5.3% of 45 to 50 years olds and 18.6% of 85- to 90-year-olds. In the...    Given the paragraphs above, decide what entity has the relation 'instance of' with 'chemical compound'.
The answer to this question is:
naftidrofuryl