17 June 2011

Is levo-methadone the answer to so-called cardiac complications?

McCance-Katz EF. (R)-methadone versus racemic methadone: what is best for patient care? Addiction 2011 106:687-688

Dear Readers,

I need to disagree with my respected colleague Dr Elinore McCance-Katz in her editorial in Addiction proposing the active isomeric formulation of methadone as a viable solution to the supposed problem with cardiac arrhythmias. She states, without any supporting reference: “Methadone confers some risk for cardiac adverse events and sudden death.” The research I have read shows that methadone actually reduces the risk of sudden death. It is also likely that methadone protects against serious cardiac events (Krantz 2001).

Addiction published Justo’s reassuring literature review of QT prolongation and torsade de pointes in methadone prescribed subjects yet now the world’s oldest dependency journal has joined the cardiac cargo cult with this piece. There are no new references for cardiac side effects, nor are we told about the recent reassuring literature from France and Norway showing the vanishing rarity of this arrhythmia in methadone patients (and a lack of reported mortality). Krantz et al 2009 is the Editorial’s main supporting reference yet this piece was so problematic that it was withdrawn and republished with an altered list of contributors, new conflict statement and changed title (see my review Click here).

Dr McCance-Katz cites this latter paper as the CSAT (Centre for Substance Abuse Treatment) consensus guideline which it was not. The terms ‘CSAT’, ‘consensus’ and ‘guideline’ were all expunged from the title in the formally re-published version (and for good reason, it would appear). CSAT’s official advice came later and was quite different from the recommendations in the Annals publication of March 2009. Krantz quotes Ballesteros, Shah, Sorg, Gagajewski as ‘a growing number’ of reports of ‘unexplained methadone-associated deaths’: yet there were none in Ballesteros; one from Sorg; none in Gagajewski; reducing, not increasing NM death rates in Shah. In practice, unexplained deaths in MMT subjects are very rare. Sudden death in the general (‘healthy’) community is reported at about 7 per 10,000 person/years (Ray 2001). It is problematic that this editorial quotes Krantz 2009 as supporting the link between methadone maintenance treatment and torsade de pointes when the evidence cited by Krantz is on shaky epidemiological grounds (Chugh's conclusions are not sustainable; Fanoe’s findings are fanciful (10-30% of OTP subjects allegedly develop unexplained syncope in a year).

Furthermore, Wedam’s RCT findings are quoted by Dr McCance-Katz and Krantz et al, despite their being consistent with the view that there is almost no risk of torsade de pointes, even in those with substantially prolonged QT intervals (>500ms). Wedam showed very high rates of QT prolongation in young patients new to treatment, yet this is the very group which rarely if ever develops torsade de pointes (vide ~100 case reports over 30 years on request).

To support the argument about the probable safety of (R)-methadone the editorial cites two studies which relate to QT intervals but not to arrhythmias. The author seems to have missed the point that QT prolongation is commonplace in methadone patients, having been reported in over 30% of patients in 1973 (Lipski). Yet such electrical observations do not appear to translate into torsade de pointes unless other factors supervene (electrolytes, other drugs, heart disease, alcohol, HIV, old age, etc). Furthermore, many or even most of the actual case reports have had normal QT intervals away from the arrhythmia episode. Justo reported a known intercurrent cause in 85% of cases. Hence these findings show the futility of ECG as a strategy to prevent torsade de pointes … and they emphasise the value of a good history and physical examination.

When thousands of patients (in Germany) are currently taking the isomeric form of methadone it would appear superfluous to examine theoretical or indirect electrical studies. Out of over 100 case reports in the literature, one single German anecdotal report describes torsade de pointes causing recurrent syncope in a patient taking racemic methadone 120mg, doxepin 100mg and a beta blocker. The patient did well when the beta blocker and doxepin were withdrawn and (R)-methadone (40mg) was substituted (Rademacher 2005). A preliminary communication on these issues from a German colleague was very reassuring, pointing out that some patients preferred the active form for its lower rate of adverse effects (constipation, sweating, sexual disturbance, etc). Swiss toxicologist Dr Chin Eap and colleagues showed that the change from racaemic to (R)-methadone led to only very modest decreases in QT interval (7.8ms two weeks after changing, p=0.06, n=39).

The French and Norwegian studies would appear to satisfy the call by Krantz and others for large national studies due to the relative low prevalence of the syndrome (sic). Norway (Anchersen, 2009) had four unexplained sudden deaths in a six year period. None was a suspected torsade case but these were the only ‘possible’ torsade deaths. Despite 15,000 patients taking methadone maintenance in France only three single torsade cases were reported to the French ‘pharmacovigilence’ department over eleven years along with seven unexplained deaths (Perrin-Terrin 2010). These figures are likely to be under-reported even though there was a nationwide awareness campaign including a ‘Dear Doctor’ letter to prescribers in France. None of the deaths was due to suspected arrhythmia yet even if they had all been due to torsade de pointes the prevalence would still be very low (0.06 per 100 patient years in the case of Norway) and may be comparable with matched subjects who are not taking methadone.

When torsade de pointes is recognised it is almost universally non-fatal. In fact, Salle and colleagues, who Krantz cites in claiming that the torsade mortality is ‘less than 20%’ in fact showed that following their initial group that over eight more years their institution had a torsade mortality of zero. Phibbs’ cardiology primer states: ‘.. torsade can be controlled 100% of the time’ which is consistent with the older French experience.

So where does this leave the baffled clinician? ‘Addiction’ has long had a bias emphasising problems with maintenance treatments in favour of demonstrating their benefits when used in appropriate circumstances (refs on request). ‘Addiction’ once published an item [Curran 1999] purporting to show that increased doses of methadone caused increased cravings (!). Letters from humble Australian and distinguished British authors on the subject were rejected so that its bizarre finding stands uncorrected to this day.

On one point Dr McCance-Katz and I agree: levo-methadone (the active isomer, (R)-methadone) is worth examining regarding its possible benefits in addiction treatments.

Comments by Andrew Byrne ..


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