In patients with end-stage renal disease, erythromycin N-demethylation by CYP3A4 was also reported to decrease; however, the alteration of erythromycin clearance was not exclusively attributed to the reduced CYP3A4 activity, but also to the changes in transporter activities (OATPs, P-gp) [44]. The gene discussed is PGP; the disease is chronic kidney disease.