Was rooting around in Medscape UK drug database because they emailed me about it. I usually use Drugs. com UK version.
In Medscape I found the following re Flecainide. "Tobacco smoke may reduce flecainide plasma level. Dosage adjustment may be required if a patient starts or stops smoking during treatment with flecainide"
Realise I'm preaching to the converted here and unlikely to be an issue, just found it interesting as have never come across it.
Also after a Google see screen shot
That's interesting and something I don't think we've ever heard about before on this forum.
"Smokers are likely to require larger doses of flecainide than non-smokers to achieve the same therapeutic effects. If a patient abruptly stops smoking be alert for flecainide adverse effects and be aware that it is likely that the dose of flecainide will need to be reduced.1 Sept 2020" Also from GP notebook. And no I'm not a doctor just nosey!!
Mentioned similar for warfarin.
I would think that for someone with afib, a flecainide dose change would be the least of a smoker's problems 
Jim
Do people still smoke? I can't think of anybody I know who still does.
Alas although rates have dropped many do! About 14% admit to smoking regularly
But still less by a considerable margin than when I was young - non-smokers were in the minority and houses regularly had yellow walls and ceilings!
I remember it well!!!
I smoke Bob. I started in 1965 and 57 years later I still buy my daily packet of cigarettes. I am well aware it is nothing to be proud of and apart from what tobacco does to one’s body it’s a senseless act of just burning money. You are not wrong in thinking no one smokes nowadays. Few do. It is now a lonely life being a smoker. I am likened to a virus. I never have company to join me in the smoke haze (my own back garden, some quiet hidden spot behind a building when I have been walking around Edinburgh for several hours or deserted hillsides and glens [I always carrying a travelling ashtray. I take the ends home) when out on a hike) I create. Ah well! No fool like an old fool or indeed a young fool as I was. After 57 years of smoking I doubt I will stop. I enjoy my cigarettes but I am fully aware of the damage they cause and I am eternally grateful that my family have had more sense than I had. They are all non smokers. I hide from them that I am still smoking but I know that ‘Mum’ is fooling no one.
Pleased you feel able to share this. My son ( 50) smokes. I remember him walking into the kitchen at 18 and saying he wanted to tell us something. I thought he'd got a girl pregnant so it softened the blow!!
I used to smoke 40 Marboro (better than the Sobrani Black Russian I smoked as a youth) a day but stopped one day in 1982 when my dying mother asked me to. Never interested me since.
Blimey Bob. Full strength but well done you for having given up all these years ago. I do wish I had made the effort but too late now. It’s not the cigarette I smoke today that’s going to get me, it’s the cigarettes I smoked 30 years ago and more. I honestly believe if I did stop my body would go into some sort of overdrive due to withdrawal of the drug and that the outcome would be no different a path than the one I am in at the moment. It is certainly not wise for me to be smoking when I have the health issues I do have. However, we are all here on this Forum. The smoker, the reformed smoker and the sensible person who never smoked a cigarette in their life. Doesn’t seem fair.
I’m an ex smoker, stopped about 5 years ago. I’m convinced it was the original trigger for my AF. Interestingly, I was prescribed flecanaide when I was still a smoker, and had a blackout shortly after starting the flec whilst smoking a cigarette. Coincidence? I think not….
Good find! To follow up with some "techy stuff", the same effect may be in play with propafenone, also:
“Drugs for which induced metabolism because of cigarette smoking may have clinical consequence include theophylline, caffeine, tacrine, imipramine, haloperidol, pentazocine, propranolol, flecainide and estradiol.”
pubmed.ncbi.nlm.nih.gov/104...
“CYP1A2 is also involved in the metabolism of proafenone “ (ncbi.nlm.nih.gov/books/NBK4....
Flecainide and beta blockers
Flecainide?
Flecainide and Tinnitus 
Flecainide - usage and dosage
Flecainide 
