Tables 4 and 5 provide a summary of the major cloned human renal tubular transport systems grouped as having either anionic or cationic substrates. Knowing the basic properties of these transport systems may be useful in predicting potential drug interactions. Methotrexate and nonsteroidal anti-inflammatory (NSAIDs) are organic anions believed to be transported by OAT1. Animal models suggest that OATs are involved in the methotrexate-NSAIDs interaction. Trimethoprim, procainamide, triamterene and histamine receptor antagonists appear to interact via OCTs. Cimetidine and trimethoprim can inhibit renal secretion of procainamide, while ranitidine and famotidine can inhibit renal secretion of triamterene.
TABLE 4 Human organic anion transport proteins (OATPs)
ACE Angiotensin-converting enzyme; CNT Concentrative nucleoside transporter; a-KG a-ketoglutarate; MRP Multidrug resistance associated protein; NSAIDs Nonsteroidal anti-inflammatory drugs; OAT Organic anion transporter; PAH Para-aminohippurate; PEPT Peptide transporter; PGT Prostaglandin transporter; SPNT Sodium-dependent purine nucleoside transporter
TABLE 5 Human renal organic cation transport (OCT) proteins
TRANSPORT PROTEINS AND HUMAN IMMUNODEFICIENCY VIRUS MEDICINE
Transport protein science appears to be particularly important in human immunodeficiency virus (HIV) medicine. As described below, P-gp efflux may lead to drug interactions involving protease inhibitors and nucleoside analogs. Nucleoside analogs such as dideoxyinosine can interfere with excretion of inosine and other endogenous nucleosides . While clinically significant interactions have not yet been reported involving SPNT or CNT1, these data suggest that the potential does exist.