PT  - JOURNAL ARTICLE
AU  - Yuri A. Kuryshev
AU  - Arthur M. Brown
AU  - Lin Wang
AU  - Claude R. Benedict
AU  - David Rampe
TI  - Interactions of the 5-Hydroxytryptamine 3 Antagonist Class of Antiemetic Drugs with Human Cardiac Ion Channels
DP  - 2000 Nov 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 614--620
VI  - 295
IP  - 2
4099  - http://jpet.aspetjournals.org/content/295/2/614.short
4100  - http://jpet.aspetjournals.org/content/295/2/614.full
SO  - J Pharmacol Exp Ther2000 Nov 01; 295
AB  - Administration of the 5-hydroxytryptamine 3 receptor class of antiemetic agents has been associated with prolongation in the QRS, JT, and QT intervals of the ECG. To explore the mechanisms underlying these findings, we examined the effects of granisetron, ondansetron, dolasetron, and the active metabolite of dolasetron MDL 74,156 on the cloned human cardiac Na+ channel hH1 and the human cardiac K+ channel HERG and the slow delayed rectifier K+ channel KvLQT1/minK. Using patch-clamp electrophysiology we found that all of the drugs blocked Na+ channels in a frequency-dependent manner. At a frequency of 3 Hz, the IC50 values for block of Na+ current measured 2.6, 88.5, 38.0, and 8.5 μM for granisetron, ondansetron, dolasetron, and MDL 74,156, respectively. Block was relieved by strong hyperpolarizing potentials, suggesting a possible interaction with an inactivated channel state. Recovery from inactivation was impaired at −80 mV compared with −100 mV, and the fractional recovery was impaired by drug in a concentration-dependent manner. IC50values for block of the HERG cardiac K+ channel measured 3.73, 0.81, 5.95, and 12.1 μM for granisetron, ondansetron, dolasetron, and MDL 74,156, respectively. Ondansetron (3 μM) also slowed decay of HERG tail currents. In contrast, none of these drugs (10 μM) produced greater than 30% block of the slow delayed rectifier K+ channel KvLQT1/minK. We concluded that the antiemetic agents tested in this study block human cardiac Na+ channels probably by interacting with the inactivated state. This may lead to clinically relevant Na+ channel blockade, especially when high heart rates or depolarized/ischemic tissue is present. The submicromolar affinity of ondansetron for the HERG K+ channel likely underlies the prolongation of cardiac repolarization reported for this drug. The American Society for Pharmacology and Experimental Therapeutics