https://marco.org/2009/04/14/those-12-hour-120mg-doses-of-pseudoephedrine
Those 12-hour, 120mg doses of pseudoephedrine (original, meth-making Sudafed) make you incredibly dizzy, woozy, and generally useless. I learned this during a sick day at home on my couch.
David has unfortunately learned this minutes before a flight to New Zealand.