Isavuconazole is a newer broad-spectrum triazole active against both Aspergillus and Mucor species. Compared to voriconazole, it has important clinical advantages EXCEPT:

• A Linear, predictable pharmacokinetics without CYP2C19 polymorphism-dependent variability
• B Broader spectrum including Candida glabrata (Nakaseomyces glabrata) that has inherent voriconazole resistance ✓
• C Available as IV and oral prodrug (isavuconazonium sulfate) that is bioconverted in the plasma by plasma esterases
• D Activity against Mucorales (mucormycosis), which voriconazole lacks

Explanation

Isavuconazole's advantages over voriconazole include: linear pharmacokinetics (predictable levels without dose adjustment for CYP2C19 genotype — voriconazole shows highly variable exposure due to CYP2C19 polymorphism), oral availability as a water-soluble prodrug (isavuconazonium sulfate, hydrolysed by plasma esterases to the active isavuconazole), and critically, in vitro activity against Mucorales (mucormycosis organisms) — a situation where voriconazole is known to be paradoxically associated with breakthrough mucormycosis. However, isavuconazole does NOT have special activity against Candida glabrata beyond other azoles; C. glabrata has reduced susceptibility to most azoles including isavuconazole, primarily due to PDR1/PDR3-upregulated efflux pumps. This is not a unique advantage over voriconazole.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

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