Battino D, Croci D, Mamoli D, Messina S, Perucca E. Influence of aging on serum phenytoin concentrations: a pharmacokinetic analysis based on therapeutic drug monitoring data. Epilepsy Res. 2004 Apr;59(2-3):155–65. doi: 10.1016/j.eplepsyres.2004.04.006. PMID: 15246117.