I've read a couple anecdotes concerning loperamide and its possible QT interval/QTc prolongation and/or cardiotoxicity and could not find true confirmation. I consider this to be "true" and should serve as a warning to those who use megadoses of loperamide for opioid withdrawal or recreation. I can't say for sure what the "safe" zone is for this drug, but these people were in the 200 - 800 mg range and it seems they were using daily. Just a heads up, be careful with lope. It seems to have a sinister side that is poorly understood.
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From: https://www.clintox.org/NACCT/2013/NAACT2013_Poster_Sessions_III.pdf - Page 6
Introduction: We report three episodes in two adults of recurrent polymorphic ventricular tachycardia (PMVT) following loperamide
abuse.
Case 1: A 43 year old female was admitted following syncope and PMVT. She reported ingestion of 140 tablets daily of loperamide
2 mg to prevent opioid withdrawal. She had recurrent PMVT requiring dozens of defibrillations, multiple medications including
lidocaine, amiodarone, sodium bicarbonate and magnesium, and eventually required transvenous pacemaker for sustained control.
Cardiac catheterization was normal. There were no further episodes of PMVT and the patient was discharged well on day 5.
Electrocardiogram (ECG) was normal with a normal QT interval. A serum loperamide level was sent however was not reported due
to laboratory error.
Case 2: A 28 year old male with a history of Crohn's disease and depression was admitted following syncope and recurrent PMVT.
His initial ECG revealed a QTc interval of 509 msec. He was treated with amiodarone and potassium supplementation and
experienced no further arrhythmias. He was discharged after 4 days with a normal ECG (QTc 430 msec). One year later the patient
was readmitted with syncope and prolonged QTc interval. The patient experienced recurrent episodes of PMVT over the first 16
hours unresponsive to magnesium, sodium bicarbonate and lidocaine. After multiple defibrillations control was achieved with a
transvenous pacemaker with overdrive pacing. The patient subsequently reported chronic abuse of loperamide, up to 400-2 mg
tablets daily for opioid withdrawal. He was discharged after 12 days with a normal ECG. A serum loperamide level on hospital day 1
was 130 ng/mL.
Discussion: Various internet sites discuss the use of loperamide for opioid withdrawal and an opioid substitute. Both patients reported
escalating use of loperamide to ameliorate opioid withdrawal. Neither was using any other drug known to affect cardiac conduction at
the time of these events. The use of a p-glycoprotein inhibitor such as quinine has been reported to enhance transport of loperamide
into the brain. Our patients denied this and both had negative quinine levels. There is only one previously published report of
ventricular tachycardia following loperamide abuse. A FDA Medwatch® query done through December 2012 reported only 3 other
cases of ventricular tachycardia, arrhythmia or death with loperamide as the only substance. Loperamide plasma levels following
therapeutic doses of 4 and 8 mg are 0.24 to 1.2 ng/mL, respectively. Our patient's level was four orders of magnitude higher.
Conclusion: Massive loperamide abuse may result in QTc prolongation and subsequent recurrent ventricular arrhythmias.
Note to mods: Feel free to move this to a more suitable location.
From: https://www.clintox.org/NACCT/2013/NAACT2013_Poster_Sessions_III.pdf - Page 6
Introduction: We report three episodes in two adults of recurrent polymorphic ventricular tachycardia (PMVT) following loperamide
abuse.
Case 1: A 43 year old female was admitted following syncope and PMVT. She reported ingestion of 140 tablets daily of loperamide
2 mg to prevent opioid withdrawal. She had recurrent PMVT requiring dozens of defibrillations, multiple medications including
lidocaine, amiodarone, sodium bicarbonate and magnesium, and eventually required transvenous pacemaker for sustained control.
Cardiac catheterization was normal. There were no further episodes of PMVT and the patient was discharged well on day 5.
Electrocardiogram (ECG) was normal with a normal QT interval. A serum loperamide level was sent however was not reported due
to laboratory error.
Case 2: A 28 year old male with a history of Crohn's disease and depression was admitted following syncope and recurrent PMVT.
His initial ECG revealed a QTc interval of 509 msec. He was treated with amiodarone and potassium supplementation and
experienced no further arrhythmias. He was discharged after 4 days with a normal ECG (QTc 430 msec). One year later the patient
was readmitted with syncope and prolonged QTc interval. The patient experienced recurrent episodes of PMVT over the first 16
hours unresponsive to magnesium, sodium bicarbonate and lidocaine. After multiple defibrillations control was achieved with a
transvenous pacemaker with overdrive pacing. The patient subsequently reported chronic abuse of loperamide, up to 400-2 mg
tablets daily for opioid withdrawal. He was discharged after 12 days with a normal ECG. A serum loperamide level on hospital day 1
was 130 ng/mL.
Discussion: Various internet sites discuss the use of loperamide for opioid withdrawal and an opioid substitute. Both patients reported
escalating use of loperamide to ameliorate opioid withdrawal. Neither was using any other drug known to affect cardiac conduction at
the time of these events. The use of a p-glycoprotein inhibitor such as quinine has been reported to enhance transport of loperamide
into the brain. Our patients denied this and both had negative quinine levels. There is only one previously published report of
ventricular tachycardia following loperamide abuse. A FDA Medwatch® query done through December 2012 reported only 3 other
cases of ventricular tachycardia, arrhythmia or death with loperamide as the only substance. Loperamide plasma levels following
therapeutic doses of 4 and 8 mg are 0.24 to 1.2 ng/mL, respectively. Our patient's level was four orders of magnitude higher.
Conclusion: Massive loperamide abuse may result in QTc prolongation and subsequent recurrent ventricular arrhythmias.
