Hi Jan,
If you prescribe itraconazole for mold-related illness, I want to share something that doesn't get enough attention—and ask for a small amount of your help.
Itraconazole absorption is notoriously variable from patient to patient, and generic formulations are especially unreliable. A patient can take a standard dose faithfully and still never reach a therapeutic blood level. The only way to know is to measure it.
This matters clinically. When a patient doesn't improve on itraconazole, it's easy to conclude the drug, or the whole mold hypothesis, has failed. But if they were never absorbing the medication, that's not a treatment failure; it's an absorption problem, and it's fixable. Left unrecognized, subtherapeutic exposure carries real risks: it can foster antifungal resistance, drive relapse, and cost patients months of time, money, and effort chasing a treatment that never had a fair trial.
We recently started measuring itraconazole trough levels in our own patients. So far, every patient we've tested has come back subtherapeutic despite standard dosing. We found that striking enough to build a paper around it, which we're preparing for peer-reviewed publication with the goal of making therapeutic drug monitoring (TDM) a routine part of prescribing itraconazole.
This is where you can help. We're collecting itraconazole level data from practices beyond our own to strengthen the picture. We want every result you have, whether the level came back subtherapeutic or therapeutic. The full range is what makes the data meaningful.
If you're willing to contribute, please go to this google form and submit the requested information without any patient identifying information by October 10th. Once submitted, the information is added into a google sheet. From there, we'll analyze the data and summarize it in the paper we're working on publishing.
If you haven't been checking levels but would like to start, here's how:
Order serum itraconazole (Quest: 94092 / Labcorp: 700833). Draw in the morning, as a trough, right before the next dose, after at least two weeks on a stable dose.
Professional Co-Op offers it for around $159, well below the typical $300–$500 elsewhere, and accounts are simple to set up.
We're genuinely grateful to anyone who contributes. Data like this is how practice actually changes, and every result you send makes the case sharper.
