Evaluation of Pharmacokinetics and Dose Proportionality of Diazepam After Intranasal Administration of NRL‐1 to Healthy Volunteers

NRL-1 is a novel intranasal formulation of diazepam that is being evaluated as rescue medication in patients with epilepsy who experience bouts of increased seizure activity despite stable regimens of antiepileptic drugs. This phase 1, open-label, randomized, crossover study in healthy adult volunteers consisted of 3 single-dose periods (5, 10, and 20 mg) followed by a 2-dose period (2 × 10 mg) with a minimum 28-day washout between treatments. Blood samples were taken at prespecified time points after intranasal dosing, and bioanalytic analysis of diazepam and nordiazepam was conducted using a validated liquid chromatography-tandem mass spectrometry method. Plasma pharmacokinetic parameters were summarized using descriptive statistics, and dose proportionality (peak concentration [C_max ] and area under the plasma concentration-time curve [AUC_0-∞ ]) was evaluated based on a power model within a 90%CI of 0.84 to 1.16. Comparisons were also conducted between single 10-mg dose and multidose (2 × 10 mg) treatments. NRL-1 administration resulted in rapid diazepam absorption (median time to peak concentration 1.4-1.5 hours). Plasma concentration-time profiles showed similar patterns of exposure that appeared to be dose dependent, with C_max of 85.6, 133.6, and 235.3 ng/mL for the 5-, 10-, and 20-mg doses, respectively, although the lower 90%CI for C_max and AUC_0-∞ exceeded dose proportionality criteria. The coefficient of variation ranged from 59% to 67% for C_max and 48% to 56% for AUC parameters. Dose-normalized AUC_0-∞ values were comparable between the 2 × 10-mg and single 10-mg doses. Treatment-emergent adverse events were consistent with those expected for diazepam, with transient somnolence the most frequent adverse event (94.4%). These results support NRL-1 as a potential therapy for managing seizure emergencies.