Interaction of digoxin with antihypertensive drugs via MDR1.

Kohji Takara, Mikio Kakumoto, Yusuke Tanigawara, Junko Funakoshi, Toshiyuki Sakaeda, Katsuhiko Okumura

Department of Hospital Pharmacy, School of Medicine, Kobe University, Japan.

Life sciences 2002 Feb 15

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The multidrug transporter MDR1 (P-glycoprotein)-mediated interaction between digoxin and 29 antihypertensive drugs of various types was examined by using the MDR1 overexpressing LLC-GA5-COL150 cells, which were established by transfecting MDR1 cDNA into porcine kidney epithelial LLC-PK1 cells. These cells construct monolayers with tight junctions, and enable the evaluation of transcellular transport. The MDR1 was highly expressed on the apical membrane (urine side). The basal-to-apical and apical-to-basal transcellular transport of [3H]digoxin in LLC-GA5-COL150 cells was time- and temperature-dependent. The basal-to-apical transport of [3H]digoxin was markedly increased, whereas the apical-to-basal transport was decreased in LLC-GA5-COL150 cells, compared with the host LLC-PK1 cells, suggesting that [3H]digoxin was a substrate for MDR1. Most of the Ca2+ channel blockers used here markedly inhibited basal-to-apical transport and increased apical-to-basal transport. Exceptions were diltiazem, nifedipine and nitrendipine, which hardly showed inhibitory effects on transcellular transport of [3H]digoxin. Alpha-blocker doxazosin and beta-blocker carvedilol also inhibited transcellular transport of [3H]digoxin, but none of the angiotensin converting enzyme inhibitors and AT1 angiotensin II receptor antagonists used here were active. These observations will promote understanding of the digoxin-drug interactions resulting from their actions on MDR1, and which may aid in avoiding these unexpected effects of digoxin.

Citation

Kohji Takara, Mikio Kakumoto, Yusuke Tanigawara, Junko Funakoshi, Toshiyuki Sakaeda, Katsuhiko Okumura. Interaction of digoxin with antihypertensive drugs via MDR1. Life sciences. 2002 Feb 15;70(13):1491-500