2012). In contrast, a single dose of 4 mg/kg sildenafil increased kidney tubular AQP2 expression in Brattleboro rats, a model of central diabetes insipidus (Bouley et al. 2005). In support of its efficacy, 200 mg sildenafil per kg food administered for 3 weeks to rats with lithium‐induced NDI, increased urine osmolality by 37% (Sanches et al. 2012). This evidence concerns the gene AQP2 and Central diabetes insipidus.