I believe that it doesn’t work wholeheartedly, because every time I try it, it is ineffective - but my sinus problems are rarely bad enough to warrant medication (it’s been one year) and by then I’ve forgotten what works and what doesn’t.

Also, I suspect you’re mixing up your drugs. Phenylephrine (the drug in this article) lacks the methyl structure to be used for the synthesis of methamphetamines. In fact, that’s why it was popularized - pseudoephedrine, the truly effective sibling, was becoming too good for meth production, so they created a less potent alternative, phenylephrine, that lacks the ingredients necessary. They then locked pseudoephedrine behind the counter. Turns out the oral form of phenylephrine is less than “weaker” - it’s largely useless - so they pumped out enough of this crap to the tune of $1.7B that the American public spent every year for 18 years after they knew.