I have a related comment, not about Sudafed but about Dextromethorphan (DM). DM is found is some over-the-counter multi-symptom cough syrups in the US. The component that supresses the cough is DM. The US National Institute of Health (NIH) is studying whether DM can help SD patients.
It might be an alternative to Botox someday, taken in pill form
or liquid.Like your experience with Sudafed, DM most likely acts on certain receptors related to the larnyx. I don't know when the study times out but I am anxious to hear the results.
By the way, Sudafed is not good for anyone with high blood pressure; taking it long term might produce some nasty results for your liver (????). I'd be afraid to use it long term. I'd rather wait until the NIH study concludes on Dextromethorphan. If they come up with something, I'm sure it would be in a safe form for long-term use.