I really feel what you’re going through.
You have a few (none of them perfect) options here:
1. Talk to your boss. See if you can wear headphones while you’re working (proper headphones that’ll block out all the coughing). Also see if you can work the odd day from home or in a quiet room in the office. Turn it into a benefit for the company. Explain that when you can work in total quiet you can get lots more done.
2. Consider changing job. It might sound dramatic, but if there are 5 or 6 people triggering you constantly this problem isn’t going anywhere, even if you’re drugged up to the eyeballs. You might find ways to cope and reset in-between triggers but you’ll subjected yourself to an exhausting regime day in day out. There are other offices and jobs and, if you’re able, there is always freelancing. Too often as misophones we feel like have to conform to the accepted ‘norm’ (cramped, noisy offices) but there are a lot of different ways to work now.
Re: Drugs. Some people have found CBD oil helps a little. To be honest drugs won’t be a truly effective or sustainable route and they don’t really work for miso. It’s a bit like trying to shoot down a bumblebee with a rocket launcher and they never silence just the miso without tinkering with something else. They’ll be unwanted side effects and possibly dependency etc etc Some might give you a temporary respite (as you’ve found with alcohol) but when they wear off the misophonia is usually exacerbated, so I would avoid going down that route.
Wishing you all the best with it.