An injection really? Sorry to dirt your mind with this all but I wouldn't vote for the injectable N-way out...
https://www.motherjones.com/environment/2017/05/lethal-injection-inquring-minds/
This is a kind of mediocre article. I've read the same criticisms of lethal injections and they are entirely valid - in general, state killings are performed primarily to not traumatise others, imo. But the article is almost entirely not about the agent being used. Potassium chloride is just not comparable to any barbiturate and is primarily responsible for the pain in that cocktail. Sodium pentothal is, as far as I know, not injected without KCl.
Where it does mention N, we do get more confirmation of the burning, though. But I can't find anywhere that it was similar to what Smedley went through. The state blamed it on impurities from the compounder—those would hurt like hell if injected (one reason to go with the oral solution, I guess... would still prefer the injection if I was going with Dignitas).
I personally thought Smedley's case was choking due to dysphagia or the taste, based on the cough, but upon review he was talking normally before the cough. Not very clear if he aspirated anything by accident afterwards.
I've struggled to find a cause for a burning sensation before, should you take the oral solution. Fever is associated with hypersensitivity, but I'm not sure that's a fever... There's nothing about the cause of death that should make you burn up. Drinking the N might make you thirsty and uncomfortable, especially with the prior fasting—especially with the really foul taste (someone on here compared it to crushed medicine held in the mouth, which I have done before), could explain the choking... Are there other examples of the phenomenon?
The only Pepto-Bismol comments I can find are related to proposed alternatives for execution not involving N, I believe for the taste of chloral hydrate. (This could be because Google is shit, I am still looking for the one Chinaski mentioned.)
I have to say though, the state of Texas is not high on my personal trust list, especially when it comes to the rights of felons. I've seen it blamed on expiration, etc. but the case was potentially important politically. So I am interested in being shown things I have missed obviously. I trust the Smedley video more, but there's a cut and one can only speculate about what he experienced because doctors have never to my knowledge publicly commented why he died like that.
And I understand that people are invested in this primarily because they are preparing to take N—I am sorry that it is so hard to make a truly informed decision and prepare for the experience.