Phenytoin enzyme induction for management of supratherapeutic tacrolimus levels due to drug-drug interaction with nirmatrelvir/ritonavir: Case series and discussion.

PURPOSE: Nirmatrelvir/ritonavir is one of few options for outpatient treatment of COVID-19, but its use has been limited in transplant recipients due to significant drug interactions with immunosuppressants. Tacrolimus toxicity is possible when the drug is coadministered with nirmatrelvir/ritonavir and may require urgent reduction of tacrolimus levels. This case series describes the use of phenytoin for enzyme induction in 5 adult solid organ transplant recipients with supratherapeutic tacrolimus levels resulting from coadministration with nirmatrelvir/ritonavir. SUMMARY: Solid organ transplant recipients are at high risk for complications related to COVID-19. Outpatient treatment options are limited, and therapeutic drug monitoring is complex in patients requiring quarantine. The 5 solid organ transplant recipients described herein were initiated on nirmatrelvir/ritonavir in the outpatient setting and subsequently presented with supratherapeutic tacrolimus concentrations greater than 59 ng/mL and developed signs and symptoms of tacrolimus toxicity. In all patients, nirmatrelvir/ritonavir and tacrolimus were discontinued, and oral phenytoin (200-400 mg/day) was given for 2 to 4 days. Tacrolimus was resumed once tacrolimus levels decreased to appropriate levels. CONCLUSION: These observations demonstrate that metabolism induction using phenytoin may be a useful strategy in the setting of supratherapeutic tacrolimus levels resulting from concomitant administration with nirmatrelvir/ritonavir.

Outcomes of hepatitis C virus nucleic acid testing positive donors in aviremic recipients with delayed direct-acting antiviral initiation.

The use of allografts from hepatitis C virus (HCV) Nucleic Acid Testing (NAT)+ donors into HCV NAT- recipients has been reported to be efficacious in a handful of studies. However, these studies have not reflected real-world practice where the initiation of direct-acting antivirals (DAA) is dependent on insurance coverage. A single-center, retrospective chart review of HCV NAT- recipients who underwent solid organ transplantation (SOT) from a HCV NAT+ donor between April 1, 2019 and May 27, 2020 was conducted. Sixty-one HCV NAT- patients underwent SOT with a HCV NAT+ organ, with 59 transplant recipients included for evaluation: 22 kidney (KT), 18 liver (LiT), 10 heart (HT), nine lung (LuT). HCV transmission occurred in 100% of recipients. Average time to DAA initiation was POD 46.3 ± 25 days. SVR12 was achieved in 98% (56/57; two patients ineligible for analysis). Treatment failure occurred in one LuT on glecaprevir/pibrentasvir with P32del and Q80K mutations. No patients developed fibrosing cholestatic hepatitis. Two patients died, secondary to anastomotic complication (LuT) and pulmonary embolism (HT). Clinically significant rejection was diagnosed and treated in two HT (one patient with ACR2 and one with ACR2/pAMR2) and one LiT (RAI 5/9). Six patients (10.2%) had documented adverse effects attributed to DAA therapy, primarily gastrointestinal.