)-. One of other compounds created was 1,2-Propanediol, 3-(2-methoxyphenoxy)-, which is commonly known today as guaifenesin. At the time, it was known as guaiacol glyceryl ether. Unfortunately, the muscle relaxant effect of propanediols only lasts a short time, due to the drugs being rapidly metabolized. That is to say, they are converted into other chemicals, and then these resulting "metabolites" are excreted in the urine. Thus, because of their short effective duration, the first propanediol drugs that were created had limited use for humans (the timed release version of guaifenesin was not created until decades later). However, they could be used in veterinary medicine, in intravenous anesthetic preparations for surgery. But another problem was that all of these drugs have a also hemolytic side effect, i.e. causing cellular destruction of red blood cells. Guaifenesin, however, has less hemolytic activity, and it also has greater water solubility, so it became the preferred drug to use.