Exploring in vitro solubility of lamotrigine in physiologically mimetic conditions to prospect the in vivo dissolution in pediatric population

Pediatric drugs knowledge still leaves several gaps to be filled, all the while many biopharmaceutic properties applied to adults do not work in pediatrics. The solubility in many cases is extrapolated to pediatrics; however, sometimes it may not represent the real scenario. In this context, the aim of this study was to assess the possibility of the extrapolation of the solubility data assumed for adults to children aged 2–12 years using lamotrigine (LTG) as a model. LTG showed that its solubility is dependent on the pH of the medium, no precipitate formation was seen, and biomimetic media showed a greater capacity to solubilize it. Based on the dose number (D₀) in adults, the LTG was soluble in acidic pH media and poorly soluble in neutral to basic. Similar behavior was found in conditions which mimic children aged 10–12 years at a dose of 5 and 15 mg/kg. The D₀ for 5-year-old children at a dose of 15 mg/kg showed different behaviors between biorelevant and pharmacopeial buffers media. For children aged 2–3 years, LTG appeared to be poorly soluble under both gastric and intestinal conditions. Solubility was dependent on the volume of fluid calculated for each age group, and this may impact the development of better pharmaceutical formulations for this population, better pharmacokinetic predictions in tools as PBPK, and physiologically-based biopharmaceutics modeling, greater accuracy in the justifications for biowaiver, and many other possibilities.