Opioid-induced respiratory depression suspected of drug interaction in a prostate cancer patient: a case report.

BACKGROUND: Many of the drugs used for the treatment and alleviation of symptoms in cancer patients are known to inhibit or induce cytochrome P450 (CYP). Therefore, it is important to pay attention to the drug interactions of opioid analgesics that are metabolized by CYPs, because for example when using oxycodone metabolized by CYP3A4, it is possible that the effect will be attenuated or enhanced by the concomitant use of drugs that induce or inhibit CYP3A4. Aprepitant, an antiemetic drug used in many patients receiving anticancer drugs, is known as a moderate competitive inhibitor of CYP3A4. We experienced a case of respiratory depression caused by opioids, which was suspected to be caused by a drug interaction with antiemetics especially aprepitant. CASE DESCRIPTION: The patient was a 72-year-old man. He had been treated with continuous oxycodone infusion for perianal pain associated with the rectal invasion of prostate cancer. No comorbidities other than renal dysfunction were observed. Oxycodone treatment was started at 48 mg/day, and was increased to 108 mg/day, and then the pain decreased. Once the pain was controlled, chemotherapy was planned. Antiemetics (dexamethasone, palonosetron, and aprepitant) were administered before anticancer drug administration. Approximately 3 hours after antiemetics administration and before the administration of the anticancer drugs, a ward nurse noticed that oversedation and respiratory depression had occurred. When the patient was called, he immediately woke up and was able to talk normally, so the anticancer drugs were administered as scheduled. About 2 hours after the nurse noticed oversedation, the attending physician reduced the dose of oxycodone infusion to 48 mg/day. After that, his drowsiness persisted, but his respiratory condition improved. Despite reducing the dose of oxycodone to less than half, the pain remained stable at numeric rating scale (NRS) 0-1, without the use of a rescue dose. The patient was discharged from the hospital 36 days after the administration of anticancer drugs, without any problems. CONCLUSIONS: The cause of respiratory depression in this case was thought to be a combination of factors, including drug interactions between oxycodone and antiemetics, and oxycodone accumulation due to renal dysfunction.

Dermatomyositis Identified During Palliative Care Management for Chemotherapy-Associated Pain: A Case Report.

Background: Skin disorders and neuropathy often occur as side effects of chemotherapy. We encountered a patient who was treated for drug-induced skin symptoms, but the symptoms did not improve, and he was eventually diagnosed as having dermatomyositis. Case presentation: A 71-year-old man underwent chemotherapy with regorafenib in February 2020 for the postoperative recurrence of sigmoid colon cancer, but treatment was discontinued after about 2 months owing to the appearance of skin symptoms, which were thought to be side effects of regorafenib. Subsequently, his symptoms further worsened, and he was hospitalized 3 weeks after the appearance of the initial skin symptoms, and a palliative care team was asked to relieve his back pain caused by the drug-induced skin symptoms. Erythema was widely observed on the lower back and limbs, and he experienced needle stick-like pain. Furthermore, the patient demonstrated difficulty in lifting both upper limbs. As acetaminophen was effective for his pain, the dose was slowly increased with careful observation. The cause of the patient's muscle weakness was unclear, and after careful discussion of the possible causes among specialists in dermatology, neurology, and rheumatoid arthritis, a diagnosis of dermatomyositis associated with the malignant tumor was made about 10 days after his admission. The patient's symptoms gradually improved with steroid pulse treatment (methylprednisolone 1 g/day for 3 days) followed by high-dose gamma globulin treatment (2.5 g/day for 5 days), and the patient was discharged 48 days after admission. Discussion: Because this patient was referred to a palliative care team for the purpose of relieving pain caused by skin symptoms associated with chemotherapy, a crucial point is the symptoms were treated as side effects of the chemotherapy from the beginning. As neuropathy can occur as a result of chemotherapy, the pain and muscle weakness could be explained at the time; however, the symptoms continued to worsen even after the chemotherapy was stopped. Because the symptoms were not typical of polymyositis/dermatomyositis, diagnosis of the patient was delayed, even though he was treated in each specialized department. Our present case indicates that paraneoplastic syndrome should always be kept in mind when treating cancer patients.