Category: transport
Phase-3 = active transmembrane transport that determines drug absorption, distribution, biliary + renal excretion. Efflux pumps (ABC family): P-glycoprotein (P-gp / ABCB1 — broad substrate; gut barrier + BBB + biliary; digoxin / colchicine / fexofenadine); BCRP (ABCG2 — overlapping with P-gp; rosuvastatin); MRP family (ABCC1-7 — glucuronide / glutathione conjugates). Uptake pumps (SLC family): OATP1B1/B3 (hepatic uptake of statins; SLCO1B1 polymorphism affects simvastatin myopathy risk); OCT2 (renal cation uptake; metformin); MATE1/2 (renal cation efflux; cobicistat blocks → mild creatinine rise). Cobicistat + ritonavir + verapamil are clinically important P-gp + OATP inhibitors. Rifampin is a P-gp inducer (digoxin AUC reduction).