Risedronate-Induced Chronic Drug Fever in a Case of Parkinson's Disease

We present an atypical case of risedronate-induced chronic fever in an 85-year-old woman with Parkinson's disease, with a dosage regimen of 17.5 mg/week. Our patient had been administered an analgesic/antipyretic drug, acetaminophen, at a rate of 600 mg/day for treatment of a vertebral fracture that occurred relatively frequently, which might have masked the fever caused by risedronate. We noted two clinically significant indications. Firstly, blood test results do not necessarily show the cause of risedronate-induced fever, as white blood cell counts and C-reactive protein levels vary. A simple way to diagnose risedronate-induced fever is to suspend risedronate for a certain period and observe if the patient's fever lowers. Secondly, in general, cases receiving polypharmacy tend to include an analgesic antipyretic agent, which may mask the drug-induced fever. Even in patients with Parkinson's disease whose body temperature is generally unstable due to autonomic nerve system disorder, if they are administered risedronate and experience chronic fever of unknown cause, the possibility of drug fever may be considered. This study concludes that risedronate-induced chronic fever, as observed in our case, represents a rare phenomenon, and it may be necessary to reconsider treatment methods for osteoporosis.