QT-Interval Effects of Methadone, Levomethadyl, and Buprenorphine in a Randomized Trial. Wedam EF, Bigelow GE, Johnson RE, Nuzzo PA, Haigney MCP. Arch Intern Med 2007 167;22:2469-2473
Dear Colleagues,
This is the latest salvo in a cavalcade of papers on the supposed cardiac associations of methadone in addiction treatment. Readers might assume from the title that this is a randomised trial looking at cardiographic changes from a new perspective. In fact it is a re-examination of study performed in the 1990s, this time with old analogue cardiograph traces salvaged and corrected QT estimations attempted. I have repeatedly written to the corresponding author over some apparent discrepancies in the methadone �rescue� group but without any resolution. Some heroin addicted patients received placebo-equivalent (20mg methadone daily) which I believe would be unethical under today�s standards.
These authors report an average corrected QT interval increased of up to 23 milliseconds 4 months into methadone treatment. We are told that 6 of 52 (12%) met clinical criteria for cardiac risk at some stage during the trial (eg. QTc > 500ms).
It appears that no patient developed tachycardia during the trial which is consistent with the literature. Torsades arrhythmia in methadone clinic patients seems to be a very rare event as I could not find a single clinician in New York recently who had ever seen a case out of tens of thousands of MMT subjects. The finding of lengthened QT timings in this trial is consistent with Lipsky�s study from 1973.
The clinical significance in causing arrhythmias is still unclear, but according to Martell, Gourevitch and colleagues: �� an increase in QTc interval of greater than 40 milliseconds [is] the generally accepted threshold for an increase that should prompt clinical concern (4). Similarly, � a QTc interval of more than 500 milliseconds is considered a definite risk for torsade de pointes regardless of sex (5) ��. By these criteria, the findings of Wedam and colleagues are consistent with a substantial theoretical risk of cardiac symptoms in �standard� methadone patients given guideline-based treatment. Yet torsade is almost unknown except for those on extremely high doses (>300mg daily), co-medication (especially alcohol and cocaine), pre-existing heart disease and/or with documented metabolic problems.
Far from conceding this conclusion, the authors find that methadone is far more likely to involve risks which can be avoided by the use of buprenorphine which they state should be considered in its place. This is a most na�ve deduction, and seems to show a lack of insight into the current state of dependency treatment (see Kakko�s trial from Sweden; Ling; Strang and others showing the limitations of buprenorphine in addiction treatment).
Having stated in the first sentence that buprenorphine and methadone are equivalent (which they are not), they state further: �Levomethadyl and methadone each have had reports of notable clinical adverse events, including TdP [refs 9-15 see below].� On closer examination, these references do not generally involve methadone maintenance cases which is what they address in their conclusions, but rather, they are complex medical and overdose cases (see below).
The mean daily dose in Krantz� original study was 397mg (n=17); Walker >600mg (n=3); Sala (n=4) mean 365mg daily; Mokwe � street methadone dose unknown (n=1); de Bels blood levels 3500mg/L and 1740mg/L (n=2) overdose cases (therapeutic range 100-1000mg/L).
Martell: (n=132) doses 30-150mg had �a small QT interval prolongation of uncertain significance� [average 12ms, mostly in males taking 110-150mg daily]. Also not cited is the world�s largest and most authoritative series from FDA reports: Pearson�s mean dose was 410mg (n=56).
The Wedam report concludes: �We know of no published cases of TdP with the use of buprenorphine� [they omit that there are virtually no reports of TdP in uncomplicated methadone maintenance patients either]. Then: �Physicians must use their judgment in choosing the appropriate therapy for opioid dependence; failure of therapy results in considerable mortality. However, given that buprenorphine has previously been proven to be equally efficacious in the treatment of opioid addiction [this is not referenced and is incorrect in my view], buprenorphine may be a safe alternative for treatment of this common and life-threatening problem.� As drug guru Walter Ling has written, finding no significant difference between treatments does NOT prove that they are equivalent.
The paper states: �Financial Disclosure: Dr Johnson is currently an employee of Reckitt-Benckiser Pharmaceuticals Inc, the manufacturer and distributor of buprenorphine. Dr Bigelow has received, or anticipates receiving, research support, through his institution, from Purdue Pharma LP, Biotek Inc, and Titan Pharmaceuticals Inc for studies of other buprenorphine formulations.�
Comments by Andrew Byrne .. http://www.redfernclinic.com/ (who is an enthusiastic prescriber of both buprenorphine and methadone in addiction medicine).
References:
Johnson RE, Chutuape MA, Strain ED, Walsh SL, Stitzer ML, Bigelow GE. A Comparison of Levomethadyl Acetate, Buprenorphine, and Methadone for Opioid Dependence. NEJM (2000) 343;18:1290-1297
Martell BA, Arnsten JH, Krantz MJ, Gourevitch MN. Impact of methadone treatment on cardiac repolarization and conduction in opioid users. Am J Cardiol. 2005;95:915-8
Pearson EC, Woosley RL. QT prolongation and torsades de pointes among methadone users: reports to the FDA spontaneous reporting system. Pharmcoepidemiol Drug Saf. 2005 14;11:747-753
Krantz MJ, Mehler PS. QTc prolongation: methadone's efficacy-safety paradox. Lancet 2006 368:556-557
Byrne A, Stimmel B. Methadone and QTc prolongation. Lancet 2007 369:366
Krantz MJ, Lewkowiez L, Hays H, Woodroffe MA, D. Robertson AD, Mehler PS. Torsade de Pointes Associated with Very-High-Dose Methadone. Ann Intern Med. (2002) 137:501-504
Walker PW, Klein D, Kasze L. High dose methadone and ventricular arrhythimias: a report of three cases. Pain 2003 103:321-4
[This summary has been up-dated with come corrections and clarifications.]
