The Pharmacokinetic Study of Progesterone and Allopregnanolone in Refractory Epilepsy : Phase II Study

Abstract Background: Progesterone belongs to a class of neurosteroids used for the reduction of seizure frequency in patients with refractory epilepsy. However, the pharmacokinetics of progesterone and its active derivative, allopregnanolone, have never been studied in these patients. Objectives: This study was aim to explore the pharmacokinetic parameters of progesterone 400 mg every 12 h, for 3 months, in patients with refractory epilepsy as an add-on therapy to control seizures. Phoenix® WinNonlin® was used to analyse the pharmacokinetic parameters. Results: Twelve patients were recruited. From a therapeutic drug monitoring, the serum progesterone and allopregnanolone levels after taking the first dose of progesterone were characterised by a time to maximum concentration (Tmax) median of 1 and 2.5 h, a maximum concentration (Cmax) median of 274.97 and 3.81 ng/mL, and a minimum concentration (Cmin) median of 56.93 and 1.06 ng/mL, respectively. The median values of the pharmacokinetic parameters of progesterone and allopregnanolone during the steady state were as follows: t1/2 of 2.4 and 2.0 h, Cmax of 964.35 and 8.92 ng/mL, and Cmin of 64.67 and 1.86 ng/mL, respectively. By examining the relationship between the progesterone or allopregnanolone concentrations with seizure-controlling ability, we could identify a responder patient group with 6- to 7-fold higher serum concentrations of progesterone and allopregnanolone than the non-responders. Conclusions: We could establish higher serum levels of both progesterone and allopregnanolone, which could consequently relate to lowering the seizure frequency in patients with refractory epilepsy. The suggested progesterone dose was 400 mg orally every 12 h against refractory epilepsy Trial registration: This study has been registered on the Thai Clinical Trials Registry (No. TCTR20200710005, 10 July 2020)