<s>[INST] context: Acute interstitial nephritis is due to a hypersensitivity reaction usually caused by a drug. Drugs implicated in the pathogenesis of acute interstitial nephritis include non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and indomethacin; beta-lactam antibiotics, such as cephalothin and methicillin; sulfonamides; diuretics, such as furosemide and thiazides; and drugs like phenytoin, cimetidine, and methyldopa. The typical presentation for acute interstitial nephritis is the development of acute renal failure, fever, a maculopapular rash, and eosinophilia. The patient's periorbital edema and wheezing are also consistent with acute interstitial nephritis. Ibuprofen is the most likely causative agent for the development of the patient's signs and symptoms. Although the exact mechanism by which NSAIDs cause this disorder is not fully understood, it is believed to be related to their ability to decrease prostaglandin formation, which leads to a reduction in renal blood flow. None of the other medications are associated with the development of acute interstitial nephritis. Acarbose is an antidiabetic agent that delays the absorption of glucose from the intestinal tract. Clonidine is a centrally-acting antihypeensive agent used in the treatment of hypeension and prophylaxis of migraines. It has been shown to be efficacious in ameliorating symptoms of alcohol, tobacco, opiate, and benzodiazepine withdrawal. It is also used in the treatment of attention deficit disorder with hyperactivity. Metformin is an antidiabetic agent that increases the binding of insulin to its receptor. One impoant side effect of metformin is the development of lactic acidosis. [/INST] question: A 72-year-old female is brought to the emergency room after the development of periorbital edema, a maculopapular rash on her chest, and a fever of 101degF (38.3degC). Laboratory examination reveals a blood urea of 77 mg/dL and a serum creatinine of 3.1 mg/dL. Urinalysis shows mild proteinuria and eosinophils, but is negative for glucose and ketones. The patient's past medical history is significant for hypeension, diabetes, and osteoahritis. Which of the following medications most likely caused the appearance of her signs and symptoms? | options: A: Acarbose B: Clonidine C: Ibuprofen D: Metformin | answer: C </s>