METHODS: A systematic electronic literature search of PubMed, Embase, the Cochrane Library and Science Direct was conducted for the period 1995-2019. In these databases, search terms describing hypokalaemia and cardiotoxicity were combined with the term laxative use.
RESULTS AND DISCUSSION: Over the 23 years, 27 incidents were identified in 12 countries. There were 19 female and eight male patients, with ages ranging from 1 month to 93 years. The frequency of reported cases according to severity was the following: severe hypokalaemia 48%, moderate hypokalaemia 44.4% and mild hypokalaemia 7.4%. In 70% of patients, the effect of laxative on the heart was typical hypokalaemic electrographic changes, 7.4% showed abnormal changes in cardiac rhythm, whereas in 18.5%, the cardiotoxicity observed was a very serious kind. Two patients died due to severe cardiac effects.
WHAT IS NEW AND CONCLUSION: The laxatives-along with the involvement of some other contributing factors-caused mild-to-severe hypokalaemic cardiotoxicity. These factors were non-adherence of the patient to the recommended dosage, laxative abuse, drug-drug and drug-disease interactions, non-potassium electrolyte imbalances and the use of herbal laxatives. We recommend that laxatives and aggravating factors should be taken into account in the assessment of patients with suspected hypokalaemic cardiotoxicity.
METHODS AND RESULTS: The rapid delayed rectifier potassium current (IKr), L-type Ca2+ current (ICa,L) and action potential duration (APD) were measured by whole cell patch-clamp. The expression of KCNH2 and cytotoxicity was determined by real-time PCR and Caspase activity measurements. After significant IKr suppression by Mitragynine (10 µM) was confirmed in hERG-HEK cells, we systematically examined the effects of Mitragynine and other chemical constituents in hiPSC-CMs. Mitragynine, Paynantheine, Speciogynine and Speciociliatine, dosage-dependently (0.1∼100 µM) suppressed IKr in hiPSC-CMs by 67%∼84% with IC50 ranged from 0.91 to 2.47 µM. Moreover, Mitragynine (10 µM) significantly prolonged APD at 50 and 90% repolarization (APD50 and APD90) (439.0±11.6 vs. 585.2±45.5 ms and 536.0±22.6 vs. 705.9±46.1 ms, respectively) and induced arrhythmia, without altering the L-type Ca2+ current. Neither the expression, and intracellular distribution of KCNH2/Kv11.1, nor the Caspase 3 activity were significantly affected by Mitragynine.
CONCLUSIONS: Our study indicates that Mitragynine and its analogues may potentiate Torsade de Pointes through inhibition of IKr in human cardiomyocytes.