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mexiletine side effects please advise

Kristina1

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Hi I was hoping others who are on or have tried mexiletine could chime in with their experience. Apologies in advance for the length of this post.

Background: I'm in the AMX0035 (amylyx) clinical trial in the open label phase meaning we know for sure I am receiving the real drug. I was told there is a possible drug:drug interaction between amylyx and mexiletine and that they want me to start mexiletine at just once per day (150mg) first for a few week while they monitor me, then they will let me try going up to twice a day (total=300mg) with continued monitoring.

I was also told dizziness is a normal/expected side effect.

So I took my first dose of mexiletine this morning shortly after my morning amylyx and other AM meds. About 15 minutes later I became suddenly extremly dizzy and unsteady and my clonus kept going off all over my body (jaw, knees, ankles, wrist) though not each area at the same time (that would have been nuts).

I also became suddenly very sad and anxious and started crying from feelings of sadness. My husband and PCA (helper) were both present trying to assist me.

My dizzyness and unsteadiness were so bad that even though my husband was assisting me to transfer from standing to sitting I somehow lost my legs and slipped past his hands and fell.

I was so anxious I took a lorazepam and they got me in my wheelchair (i was not even safe on my walker) and I finally felt calm enough when the lorazepam kicked in. But I remained unable to walk until around 3pm, needing assistance with getting on/off toilet (something I can normally do by myself with hand rails).

Is this within the range of a normal response to first dose? Or should I suspect it was caused or worsened by interactions with my clinical trial drug?
 

sassy

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My husband started taking it last month and has not had any side effects.

Sassy
 

KarenNWendyn

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Here’s what I found on Mexiletine side effects:

Adverse Reactions
>10%:
Cardiovascular: Exacerbation of cardiac arrhythmia (10% to 15%; patients with malignant arrhythmia)
Central nervous system: Dizziness (11% to 25%), ataxia (10% to 20%), nervousness (5% to 10%), unsteady gait
Gastrointestinal: Gastrointestinal distress (41%), nausea (≤40%), vomiting (≤40%)
Neuromuscular & skeletal: Tremor (13%)
1% to 10%:
Cardiovascular: Palpitations (4% to 8%), chest pain (3% to 8%), angina pectoris (2%), ventricular premature contractions (1% to 2%)
Central nervous system: Insomnia (5% to 7%), numbness (fingers or toes: 2% to 4%), depression (2%), paresthesia (2%), confusion, headache
Dermatologic: Skin rash (4%)
Gastrointestinal: Constipation (≤5%), diarrhea (≤5%), xerostomia (3%), abdominal pain (1%)
Neuromuscular & skeletal: Weakness (5%), arthralgia (1%)
Ophthalmic: Blurred vision (5% to 7%), nystagmus (6%)
Otic: Tinnitus (2% to 3%)
Respiratory: Dyspnea (3%)

So stomach upset, dizziness, and palpitations are most likely. Depression has been reported and nervousness.

I couldn’t find info on Amylyx to know if there is an interaction.

I recommend you check in with the neurologist.
 

Kristina1

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So I just happned to get all the CNS adverse reactions and the neuromuscular? even though they were less likely.

I already emailed neuro but it's the weekend so I havent heard back yet. Neuro is the site investigator for the amylyx trial she is the one advised me there might be a drug interaction with mexiletine but i was under the impression the interaction would have cardio side effects. though she didnt say explicitly what theyre worried about so im anxious to hear back from them on this.

in the meantime ill see if it is any better tomorrow in case i need to adjust to it
 

Nikki J

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It sounds like a truly awful experience. I am sorry.

My sister took it twice a day and tolerated it well. She was petite like you.

Was anyone able to check your blood pressure and pulse while this was happening?

You are taking it for cramps?
 

Kristina1

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yes taking it for cramps. no one rook vitals no. but they are sendinng VNA to monitor and they start today so im sure they will
 

Nikki J

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If you are planning to take it today ( and in your place I am not sure I would without hearing from my doctor) do it when the vna is there so if you have a reaction you can get things checked while it is happening. Does anyone there have a wearable device that tracks heart rate you can borrow?
 

lgelb

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One of the ingredients in AMX is sodium phenylbutyrate, which affects ammonia levels. That can definitely potentiate the effects of any other drug that can affect heart rhythm such as the mexiletine. And that same ingredient can affect mood as a known side effect.

I would not take both again unsupervised.
 

Kristina1

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I took it again with vna care present. I took it before taking the amylyx drug. Initially experienced only mild unsteadiness. About 15 minutes later I took the study drug. Right away things went downhill. Extreme dizziness, weakness, unsteadiness, anxiety, and nausea (though I had not had nausea yesterday). Vitals were ok except O2 saturation which way only 89%. No idea if that was related, but I'm guessing not. I immediately got on my BiPAP.

I've decided not to continue mexiletine.
 

Nikki J

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Sorry it did not work out but I think you made a wise decision. I hope you find another way to control the cramping
 

Doglady

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Those are really bad sounding side affects. More than I’ve ever had on mexiletine. I had miserable nausea at first so careful now to take it only with a meal and have no problems. Good luck. Your doctor should be able to help you decide which of the two drugs or the combination is the cause.
 
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