Drug Interaction between Paxlovid and Tacrolimus in an Adolescent with Inflammatory Bowel Disease

ABSTRACT

The coronavirus disease of 2019 (COVID-19) caused by SARS-CoV-2 virus led to a worldwide pandemic. Emergency use of an investigational medication, Paxlovid, was approved for patient 12 and older who tested positive for COVID-19 and at high risk for severe infection. Inflammatory Bowel Disease (IBD) is a chronic condition causing inflammation in the gastrointestinal tract. Ulcerative Colitis (UC) is a type of IBD centralized in colon and commonly treated with Immunosuppressive drugs. We present an adolescent with UC treated with paxlovid due to being on tacrolimus who developed with suspected tacrolimus toxicity. CASE REPORT A 13-year-old female with UC presented to the ED with vomiting and fatigue after paxlovid ttreatment for COVID. The patient's UC treatment included tacrolimus along with ustekinumab. She had been diagnosed with SARS-CoV-2 and prescribed Paxlovid bid x 5 days due to immunosuppressive status. Tacrolimus was held during treatment. Once paxlovid completed, tacrolimus was restarted. Two days later, patient presented to ER for vomiting, fatigue, headaches and myalgia. Labs revealed a tacrolimus level of >60 ng/ml . Electrolytes and Creatinine were normal. Toxicology felt this was due to interaction between paxlovid and tacrolimus. Patient advised to hold tacrolimus for 48 hours and repeat levels were 15.8 ng/ mL. Symptoms resolved and level repeated three days later and was 2.9 ng/mL DISCUSSION: Tacrolimus is an immunosuppressant, commonly used for management of organ transplants but also been found effective in treatment of IBD. Tacrolimus requires close monitoring as toxicity may lead to acute or chronic kidney disease. The normal concentration is between 5-15 ng/mL. Due to rapid escalation of the COVID-19 pandemic, Paxlovid was approved for emergency use for treatment of high-risk patients. It is administered as a 5-day oral course consisting of nirmatrelvir and ritonavir. Our patient was prescribed Paxlovid due to risk secondary to immunosuppression. She was appropriately instructed to stop tacrolimus. Ritonavir is a cytochrome P450 3A inhibitor and can increase plasma concentration of tacrolimus. She restarted tacrolimus treatment 12 hours after her last dose of Paxlovid and presented with symptoms and a level consistent with toxicity. This level was concluded to be due to drug interaction between tacrolimus and Paxlovid. After further withholding of tacrolimus, symptoms improved, and levels normalized. Previous reports in transplant population stress importance of decreasing the dose of tacrolimus or withholding during the course of paxlovid treatment. This case demonstrates the importance of not only ceasing tacrolimus when administering paxlovid, but continuing discontinuation for longer period post completion of therapy to minimize interactions.