Isavuconazole Capsules Should Not Be Routinely Crushed
The FDA-approved drug label does not support crushing isavuconazole capsules, and guidelines consistently specify administration as intact capsules or tablets. However, emerging real-world evidence demonstrates that opened capsules administered via enteral feeding tubes can achieve therapeutic drug concentrations when combined with therapeutic drug monitoring (TDM).
Official Guidance
The available guidelines consistently recommend isavuconazole be given "intravenously or by oral tablet/capsule" without any mention of crushing or opening the formulation 1, 2, 1. The FDA labeling does not provide instructions for crushing or opening capsules 3.
Real-World Evidence for Opened Capsules
Despite the lack of official approval, published case series provide important practical data:
A 2022 retrospective review of 37 patients receiving enteral feeding tube (EFT) administration of opened isavuconazole capsules showed that 83.3% achieved therapeutic plasma concentrations on first assessment (mean level 2.07 ± 1.1 mg/L), with nearly all subtherapeutic patients reaching target levels after dose titration 4.
A 2019 case report documented therapeutic trough levels (2.7-4.0 mcg/mL) when isavuconazole capsules were opened and administered through a gastrostomy-jejunostomy tube, comparable to intact capsule administration 5.
Clinical Approach When Crushing/Opening Is Necessary
If a patient cannot swallow intact capsules and IV administration is not feasible:
Prioritize IV formulation first - Isavuconazole IV does not contain cyclodextrin and avoids absorption concerns 6
If EFT administration is unavoidable:
- Open capsules (do not crush the beads inside)
- Use standard maintenance dosing initially (200 mg daily after loading)
- Implement mandatory TDM - Check trough levels after 5-7 days at steady state
- Target trough concentrations: ≥1 mg/L for prophylaxis, ≥2 mg/L for treatment 4, 7
- Adjust doses based on measured levels
Monitor for tube occlusion - The capsule contents may pose mechanical risks to feeding tubes
Important Caveats
- Children <6 years require higher weight-based dosing due to accelerated clearance (lower C/D ratios) 7
- ICU patients may need dose optimization due to enhanced clearance and larger volume of distribution 8
- Patients >120 kg may have lower plasma exposures and require closer monitoring for breakthrough infections 3
Bottom Line
While not officially approved, opened isavuconazole capsules administered via EFT with rigorous TDM can achieve therapeutic concentrations when no alternative exists. This practice requires close pharmacokinetic monitoring and should only be used when IV therapy is contraindicated and the patient cannot swallow intact formulations.