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Rationale of a lower dexamethasone dose in prenatal congenital adrenal hyperplasia therapy based on pharmacokinetic modelling

Viktoria Stachanow, Uta Neumann, Oliver Blankenstein, Uwe Fuhr, Wilhelm Huisinga, Robin Michelet, Nicole Reisch, and Charlotte Kloft

Context

Prenatal dexamethasone therapy is used in female foetuses with congenital adrenal hyperplasia to suppress androgen excess and prevent virilisation of the external genitalia. The traditional dexamethasone dose of 20 µg/kg/day has been used since decades without examination in clinical trials and is thus still considered experimental.

Objective

As the traditional dexamethasone dose potentially causes adverse effects in treated mothers and foetuses, we aimed to provide a rationale of a reduced dexamethasone dose in prenatal congenital adrenal hyperplasia therapy based on a pharmacokinetics-based modelling and simulation framework.

Methods

Based on a published dexamethasone dataset, a nonlinear mixed-effects model was developed describing maternal dexamethasone pharmacokinetics. In stochastic simulations (n = 1000), a typical pregnant population (n = 124) was split into two dosing arms receiving either the traditional 20 µg/kg/day dexamethasone dose or reduced doses between 5 and 10 µg/kg/day. Target maternal dexamethasone concentrations, identified from the literature, served as a threshold to be exceeded by 90% of mothers at a steady state to ensure foetal hypothalamic-pituitary-adrenal axis suppression.

Results

A two-compartment dexamethasone pharmacokinetic model was developed and subsequently evaluated to be fit for purpose. The simulations, including a sensitivity analysis regarding the assumed foetal:maternal dexamethasone concentration ratio, resulted in 7.5 µg/kg/day to be the minimum effective dose and thus our suggested dose.

Conclusions

We conclude that the traditional dexamethasone dose is three-fold higher than needed, possibly causing harm in treated foetuses and mothers. The clinical relevance and appropriateness of our recommended dose should be tested in a prospective clinical trial.

Free access

Response to ‘Hydrocortisone suspension formulations are not necessarily the same in the treatment of children with congenital adrenal hyperplasia’

Robin Michelet, Johanna Melin, Zinnia P Parra‐Guillen, Uta Neumann, Martin J Whitaker, Viktoria Stachanow, Wilhelm Huisinga, John Porter, Oliver Blankenstein, Richard J Ross, and Charlotte Kloft

Free access

Paediatric population pharmacokinetic modelling to assess hydrocortisone replacement dosing regimens in young children

Robin Michelet, Johanna Melin, Zinnia P. Parra-Guillen, Uta Neumann, J Martin Whitaker, Viktoria Stachanow, Wilhelm Huisinga, John Porter, Oliver Blankenstein, Richard J. Ross, and Charlotte Kloft

Context:

Accurate hydrocortisone dosing in children with adrenal insufficiency is important to avoid the risks of over and under treatment including iatrogenic Cushing’s syndrome and adrenal crisis.

Objective:

To establish a population pharmacokinetic model of hydrocortisone in children and use this to refine hydrocortisone replacement regimens.

Design and methods:

Pharmacokinetic study of hydrocortisone granules, available in 0.5, 1, 2 and 5 mg dose strengths, in 24 children with adrenal insufficiency aged 2 weeks to 6 years. Cortisol concentrations quantified by LC-MS/MS were used to refine an adult pharmacokinetic model to a paediatric population model which was then used to simulate seven different hydrocortisone treatment regimens.

Results:

Pre-dose cortisol levels were undetectable in 54% of the 24 children. The developed pharmacokinetic model had good predictive performance. Simulations for the seven treatment regimens using either three- or four-times daily dosing showed treatment regimens delivered an AUC0- 24h within the 90% reference range for healthy children except in neonates where two regimens had an AUC below the 5th percentile. Cortisol concentrations at individual time points in the 24 h were outside the 90% reference range for healthy individuals in 50%, 55–65% and 70–75% for children, infants and neonates, respectively, with low cortisol levels being most prevalent.

Conclusions:

Current paediatric hydrocortisone treatment regimens based on either three- or four-times daily administration replicate cortisol exposure based on AUC0- 24h, but the majority of cortisol levels are above or below physiological cortisol levels with low levels very common before the next dose.