Recent studies have shown the new posaconazole delayed-release tablets have superior bioavailability compared with the liquid suspension formulation. As higher serum posaconazole concentrations have been associated with improved clinical responses, this formulation has been a welcome addition to available treatment options. However, higher serum and tissue levels are likely to reveal previously undescribed toxicity as adverse events attributed to “off-target” effects are observed.
We prospectively identified two patients with new onset hypertension, hypokalemia, and alkalosis after starting posaconazole tablets. Patient vital signs and laboratory values were within normal limits prior to starting posaconazole; however, following over 30 days of therapy both patients became newly hypertensive (mean systolic BP increase 59 mmHg). Serum posaconazole levels were 4.3–4.6 μg/ml. Complete suppression of renin and aldosterone, with increased 11-deoxycortisol, estradiol levels, and cortisol/cortisone ratios were observed in both patients. The TTKG in both patients was inappropriately elevated.
Posaconazole-induced disruption of the steroid biosynthesis pathway in patients has not previously been described, but has been suggested by in vitro studies. Our patients’ laboratory results show clinically significant inhibition of 11β-hydroxysteroid dehydrogenase enzyme type 2 isoform (11β-HSD2) as evidenced by: the elevated 11-deoxycortisol (with subsequent suppression of renin and aldosterone), the highly elevated cortisol/cortisone ratio, and the inappropriately elevated TTKG in the setting of hypokalemia. The normal deoxycorticosterone confirms normal function of 11β-hydroxylase and the observed effects in our patients are thus downstream from this enzyme.
Our findings support in vitro predictions and highlight the clinical sequelae of posaconazole-mediated inhibition of 11β-HSD2. Additional studies are necessary to determine the frequency of posaconazole induced apparent mineralocorticoid excess syndrome and whether other azole antifungals can be associated with this phenomenon.