Acute renal failure after ibutilide

Targeting BKCa Channels in Migraine: Rationale and Perspectives

Large (big)-conductance calcium-activated potassium (BK_Ca) channels are expressed in migraine-related structures such as the cranial arteries, trigeminal ganglion and trigeminal spinal nucleus, and they play a substantial role in vascular tonus and neuronal excitability. Using synthetic BK_Ca channels openers was associated with headache as a frequent adverse effect in healthy volunteers. Additionally, BK_Ca channels are downstream molecules in migraine signalling pathways that are activated by several compounds known to provoke migraine, including calcitonin gene-related peptide (CGRP), pituitary adenylate cyclase-activating polypeptide (PACAP) and glyceryl trinitrate (GTN). Also, there is a high affinity and a close coupling between BK_Ca channels and ATP-sensitive potassium (K_ATP) channels, the role of which has recently been established in migraine pathophysiology. These observations raise the question as to whether direct BK_Ca channel activation can provoke migraine in migraine patients, and whether the BK_Ca channel could be a potential novel anti-migraine target. Hence, randomized and placebo-controlled clinical studies on BK_Ca channel openers or blockers in migraine patients are needed.

Female preponderance in ibutilide-induced torsade de pointes

OBJECTIVE

Ibutilide, a class III antiarrhythmic agent used for pharmacological cardioversion of atrial arrhythmias, has a potential to cause QT-interval prolongation and torsade de pointes. Purpose of this study was to determine whether women are more prone to develop ibutilide-induced torsade de pointes.

METHODS

All clinical trials, cases, case series, and related articles in English-language in addition to 51 patients from our institution on the subject were examined.

RESULTS

In a database derived from 23 reports in literature and from our institution, 1720 patients received ibutilide for cardioversion of atrial arrhythmias. Only in 87% (n=1492) patients, data were reported whether or not ibutilide caused torsade de pointes. The overall incidence of torsade de pointes was 3.9% (n=58) patients. Data on sex distribution of ibutilide-induced torsade de pointes was available in 73% (n=1096) patients. Torsade de pointes developed in 17 (5.6%) of 304 women and 24 (3%) of 792 men (P=0.05). It occurred during or within 45 min after completion of the infusion of ibutilide. Treatment instituted was with intravenous magnesium sulfate alone in 14% (n=8) patients, magnesium sulfate plus lidocaine in 5% (n=3) patients, magnesium sulfate with electrical cardioversion in 17% (n=10) patients, electrical cardioversion alone in 19% (n=11) patients, and precordial thump in 3% (n=2) patients. In 41% (n=24) of patients who developed torsade de pointes, it resolved without treatment. There were no reported deaths secondary to torsade de pointes associated with ibutilide infusion.

CONCLUSION

Incidence of ibutilide-induced torsade de pointes is higher in women than in men. Greater caution must be observed while using ibutilide in women.