Harm Reduction Maximal safe dosage of methadone, regarding cardiac side effect potential?

[Limpet_Chicken]

Title says it all really.

What is the maximal safe dosage of methadone daily, or spread out over two days (nights included, twice daily dosing, perhaps very small boosters, 15-20mg per a couple of times daily to prop up plasma levels)

With regards to cardiac side effects, as methadone can prolong the Q-T interval of the heart's electrophysiological cycle.

Couple of weeks ago, had to use a fair bit of methadone, 70x5mg, over two days and a night, and while I think it might be co-incidence, as I've had it happen before totally unconnected to methadone, a second episode involving a heart scare, ECG showed a sinus tach, asked the paramedics if they saw any prolongation of the QT interval, at which, for some reason they looked most surprised at the question, but the answer, was no. None.

This HAS happened before, again, sinus tach, uneventful aside from both times doing a fair job of scaring the piss out of me for obvious reasons.

No stimulant use, aside from a clinically insignificant quantity of caffeine, whatever is contained in a couple of mouthfuls of coke (beverage sort of coke), enough to wash some medication down, but that aside, none.

Opioid tolerance is not the issue here. Well not directly in the sense of potential OD.

My tolerance to opioids is high, and this, the methadone, it's an occasional measure when either pain becomes intolerable and my rx morphine/oxy cannot deal with it, or cannot do so long enough, I'm not scripted it.

BUT, I need to take large doses, 500mg/2 days isn't much, tolerance wise, in terms of opioid agonist effects.

I'm more concerned whether it may cause cardiac side effects at the kinds of dosages required to function in terms of opioid tolerance. Because I'm fairly sure, given the choice on it's part, any cardiotoxicity would knock me off long before MOR agonism would do so.

 

[Jekyl Anhydride]

I don't honestly think there's a set number where everyone will experience QT-P(rolongation) that continues into TdP, arrhythmia or Premature ventricular contractions. At the clinic where I volunteered as a patient advocate some people had issues at far lower doses than others.

Although most sudden cardiac arrests on MMT have been reported at high doses, life-threatening arrhythmias have been described at dosages as low as 29 mg/day

The risk of drug-induced ventricular arrhythmia is modulated by clearly identified predisposing factors including hypokalemia, structural heart disease, hepatic cytochrome P450 inhibitors, and genetic predisposition. At least one of these risk factors was present in the majority of documented cases of ventricular arrhythmias in MMT patients.

I would def make sure to keep up a solid intake of Magnesium as that's part of the treatment for QTP.

The initial management of a MMT patient presenting with QTP and polymorphic ventricular ectopy or TdP includes magnesium supplementation, isoproterenol and temporary pacing if arrhythmia persists

http://www.innovationsincrm.com/car...163-qt-prolongation-arrhythmia-risk-methadone

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4747000/

Another interesting finding was that 1/2 dose (R)-methadone (used in Germany) had a lower tendency to cause QTP vs full dose (R,S)-methadone, without loss of efficacy.

 

[Limpet_Chicken]

Not sure if it's enantiopure or racemic, physeptone, an english brand.

TY for the advice about Mg levels, Will have to convert some of the sulfate into the citrate or ascorbate (MgSO4 has awful oral BA, and is liable to give one the shits first)

I did wonder about hypokalaemia actually, so had been making sure to keep up a solid intake of bananas, watermelon juice (also rich in K)

Especially due to the rather high sodium levels in my diet atm, Broke means existing on porridge for a bit, although xmas dinner will negate that for a bit until I next get paid, unless of course..certain...things...can be readied in sufficient time...but anyhow, I admit, not the healthiest way to make it, but I tend to add a generous chunk of salty butter and a fair pile of salt in there when I make it.

The heart issue, both times has been a sinus tachycardia, the first time a tachyarrhythmia, this being quite some time back, this year, but a good long while back, this time, an uncomplicated sinus tachycardia, no ventricular involvement, and as mentioned, on enquiring, was told there was no QT prolongation.

29mg methadone? damn, one would need a pretty tiny tolerance to be covered by that.

As for beta-blockers, can't stand them, ugh, been given propranolol and also atenolol before whilst banged up on remand, so they could say they tried to do something and still make sure nobody gets anything potentially remotely 'fun', for anxiety, and they made me feel downright ill. I take clonidine though daily, and tizanidine (which actually helped a fair bit the other time, the recent one a couple of weeks ago)

Certainly helped bring my heart rate down. (the tizanidine I use as a myorelaxant, after some knee surgery went arse over tit, left me with neuropathy, causing a permanent contraction in the calf on that side. Hurts like a bastard otherwise, until I got on the tizanidine. The clonidine, it's something I take to prevent my overloading [in the autie sense], but together they seemed to help quite a lot.

And I wasn't expecting a precise figure. Biological systems just don't work that way. More of a ballpark 'heading into danger territory for the average human, based solely on potential cardiac side effects, rather than tolerance to opioids'. I could probably take 500mg in one dose, opioid-wise and be none the worse for it. Not about to try it to prove a point to myself, but I doubt it'd be more than 'nodding hard as fuck for the rest of the day' territory, not in OD ranges.