ABCG2 and amyotrophic lateral sclerosis: Other drugs that are ABCB1/ABCG2 substrates include HIV protease inhibitors (Kim et al., 1998a,b; Lee et al., 1998), the dopamine hydroxylase inhibitor etamicastat (Bicker et al., 2018), riluzole, one of the few Food and Drug Administration (FDA)-approved drugs for amyotrophic lateral sclerosis (ALS) therapy (Jablonski et al., 2014), and a myriad of drugs including opioids (Letrent et al., 1999; Dagenais et al., 2004; Bauer et al., 2006; Sharma and Ali, 2006; Hassan et al., 2007; Yousif et al., 2008, 2012; Chaves et al., 2016; Schaefer et al., 2018).