Although there are selective PDE4 inhibitors for treating asthma, such as roflumilast, the poor solubility in normal saline makes spray administration impossible, hence aminophylline, a nonselective phosphodiesterase inhibitor, was selected as the positive control (Campbell et al., 1977; Myou et al., 2003; Hsu and Bajaj, 2020; Zafar and Zulfiqar, 2020). This evidence concerns the gene PDE4A and asthma.