Is naltrexone a vasodilator? [Edit: Probably not]

[kushami]

I can’t find anything either way, but it feels like it is having a vasodilating effect on me – classic hot, red face and hot hands and feet – plus it has possible side effects of dizziness and fainting listed.

Maybe it’s not a vasodilator, but has some similar effect?

 

[pamojja]

As someone using low dose Naltrexone, my best guess it's not.

perplexity.ai answers this way:

Naltrexone is not a vasodilator. In fact, it can have the opposite effect in certain contexts. Here's a detailed explanation:

Naltrexone's Effects on the Cardiovascular System​

Naltrexone is a pure opioid antagonist that primarily works by blocking opioid receptors
4
. Its effects on the cardiovascular system are complex and often indirect, resulting from its interaction with endogenous opioid systems.

Blood Pressure Effects​

Rather than causing vasodilation, naltrexone can potentially increase blood pressure:

1. Naltrexone may reverse the vasodilatory effects of endogenous opioids, which can lead to a slight increase in blood pressure
   3
   .
2. An increase in arterial blood pressure is mentioned as a possible side effect in the prescribing information for naltrexone
   3
   .

Interaction with Endogenous Opioid System​

Naltrexone's cardiovascular effects are largely due to its blockade of endogenous opioids:

1. Endogenous opioids typically cause vasodilation and blunt baroreceptor reflexes
   3
   .
2. By blocking these effects, naltrexone can indirectly lead to vasoconstriction and increased blood pressure.

Effects on Heart Rate​

Naltrexone has been shown to dampen alcohol-induced increases in heart rate and diastolic blood pressure
5
. This effect is not due to vasodilation, but rather to naltrexone's ability to modulate the autonomic nervous system's response to alcohol.

Comparison to True Vasodilators​

Unlike true vasodilators, such as ACE inhibitors, naltrexone does not directly cause blood vessels to dilate:

1. ACE inhibitors lower blood pressure through vasodilation by inhibiting the formation of angiotensin II and preventing the degradation of bradykinin
   2
   .
2. Naltrexone, in contrast, can potentially increase blood pressure by blocking the vasodilatory effects of endogenous opioids
   3
   .

In conclusion, naltrexone is not a vasodilator. Its cardiovascular effects are primarily related to its antagonism of opioid receptors, which can lead to indirect effects on blood pressure and heart rate. These effects are generally mild and not the primary therapeutic action of the drug, which is used mainly for treating opioid and alcohol dependence
4

Is there any supplement or medication you take together, which could either be alone or in combination, be responsible for your observed effect?

 

[kushami]

@pamojja , thank you for that. I tried asking Perplexity too but I mustn’t have phrased my question very well.

No, LDN is the only new thing I have added.

It is weird because I get a red, hot face and my hands and feet get hot at the same time each day since I started LDN. Maybe my blood pressure is going up – I have had a hot, red face from that in the past. Not in conjunction with hot hands and feet though.

Will check blood pressure next time it happens.

 

[kushami]

The other odd thing is that it is having an immediate effect that then wears off. Is this normal? I can’t believe it is doing anything autoimmune so quickly (i.e. from the first dose).

All I can think is that it is affecting cerebral blood flow, because I know that’s where my problems lie.

It’s not just the mild euphoric effect that some people have described, because I managed to cook an omelette today, something I couldn’t normally do because of cognitive problems, and on previous days since starting it I have also prepared simple meals without disaster striking.

Prior to that, my baseline at meals was “crying and making a bad cheese sandwich” (except for when a family member kindly helps me).

 

[pamojja]

– classic hot, red face and hot hands and feet –

On its own, it sounds exactly like a niacin-flush. Do you take any supplement with niacin with the LDN?

LDN is the only new thing I have added.

Always consider, too, that new medications always can cause new symptoms from already taken supplements through new unknown interactions.

 

[JES]

What dosage are you using? I don't notice much vasodilating effect from LDN and my body is quite sensitive to that.

 

[bad1080]

i've seen reports of people usually being cold feeling warm all of a sudden but idk how that effect comes about.

 

[kushami]

@pamojja , I did try niacin a long time ago and had that effect (the niacin flush).

I got the hot face after going to bed last night but was too lazy to get up and check my blood pressure.

 

[kushami]

Hmm, it seems it’s not vasodilation, judging by everyone’s input. Thank you kindly for your thoughts and experience.

Must be some other action that is helping my brain to make omelettes!

I will check my blood pressure and see whether it is going up when I get the red face. I am not concerned about it because my face is not burning hot or blotchy and I do not get a headache (a reaction I had some years ago when my BP went paradoxically high in reaction to verapamil, a blood pressure medication). Plus it only lasts half an hour or so.

Positive effects continued today, although I am still getting side effects as well. Fingers crossed they go away and the good effect continues.

 

[kushami]

@JES , I think I was mistaken. It must be doing something else by a different mechanism to help my symptoms.

I’m taking 0.05mg twice a day, but I might reduce to once a day when I work out the optimal timing.

EDIT: I should have written 0.5mg, i.e. half a milligram.

Have you been taking it long?

 

[kushami]

@bad1080, that is interesting. I don’t usually feel cold, and, apart from sometimes waking up with numb arms, my general circulation is okay.

My vasoconstriction problem is only in the brain. I jokingly call it “Raynaud’s of the head”. although that’s not very accurate, but it sometimes gets the point over to puzzled medical personnel.

 

[JES]

@JES , I think I was mistaken. It must be doing something else by a different mechanism to help my symptoms.

I’m taking 0.05mg twice a day, but I might reduce to once a day when I work out the optimal timing.

Have you been taking it long?

0.05 mg. Oh, wow. Yeah that's not an issue with too high dosage then. I take around 2 mg per day. When I had worse OI/POTS issues I reckon I noticed a bit more ANS effects from LDN. Now I can tolerate 2 mg just fine, so as with many things, it seems you can never know what to expect with ME/CFS.

 

[Zebra]

Hmm, it seems it’s not vasodilation, judging by everyone’s input. Thank you kindly for your thoughts and experience

I was just coming back to this thread in case my experience with LDN might be useful to you.

I recently tried LDN for two months.

I experienced unusual warmth, like a hot flash, but more widespread and longer lasting. This was notable, because I'm one of those girls that is cold all the damn time.

I also experienced worsening venous pooling, from my butt down through my toes and my BP was quite low, most days the systolic was below 100 and my HR was regularly elevated.

The latter, on top of other side effects, led my physician to suggest that we table the LDN for now and try again if/when my nervous system is calmer, less irritated.

Feel free to ignore this post if not helpful to you!

 

[kushami]

@Zebra, I’m sorry it didn’t work so well. Low blood pressue and extra blood pooling would not be pleasant.

It’s always helpful to hear about other people’s experiences, especially with LDN when there’s not a lot of studies done on the effects of the lower dose generally, let alone specific to us.

 

[kushami]

@JES, I put my decimal point in the wrong place. I’m taking 0.5mg twice a day.

Sorry!

 

[kushami]

It turns out that some of what I thought were side effects from LDN were in fact due to an impending attack of BPPV (benign thingie vertigo).

Probably the headache, general blah feeling, and definitely the dizziness. (Not the hot face and extremities though.)

Had a rotten night with it but did Epley manoeuvre today and seem to be recovering.