Formulation and stability study of an oral paediatric phenobarbital 1% solution containing hydroxypropyl-β-cyclodextrins.

Objectives: Phenobarbital is a barbiturate, used to treat focal and generalised epilepsy. Since the end of marketing of the oral solution KANEURON in 2017, phenobarbital tablets remain the only available dosage form. Development of an oral phenobarbital solution for paediatric use is therefore essential to fulfil clinical needs. A new formulation of phenobarbital with hydroxypropyl-β-cyclodextrins (HPBCD) was developed, and the physicochemical stability of the solution was evaluated.

Methods: Different excipients have been selected to formulate a solution of phenobarbital. Samples were dosed by High Performance Liquid Chromatography (HPLC) at 216 nm with a LiChroCART C18 endcapped column and mobile phase composed of phosphate buffer pH 3 and methanol (50:50 v/v). Linearity, accuracy, sensibility and specificity of the method were tested, and a forced degradation study was carried out. During stability study, content of phenobarbital, pH, osmolality of the phenobarbital solution and degradation products were followed up for 6 months in line with GERPAC guidelines.

Results: The stability indicating the character of the assay method has been validated. The physicochemical stability study shows that the phenobarbital solution formulated is stable for 6 months, in line with International Conference of Harmonisation (ICH) recommendations Q1A and Q3B (R2) regarding the content of phenobarbital and levels of degradation products (no degradation products >0.01%). Phenobarbital concentration was 101.59±2.6% of initial concentration in refrigerated samples and 101.14±0.5% at 20±5°C. No phenobarbital degradation products (>0.01%) were observed throughout the 6 months. No significant variation of pH or osmolality was observed.

Conclusions: HPBCD solubilise phenobarbital and create a homogeneous solution. These stability data set the shelf life of this new phenobarbital solution at up to 6 months. A microbiological stability study will be carried out to ensure the possibility of using this solution in children.