(However, a potentially fatal adverse reaction does exist when it's injected intravenously: laryngospasm, a condition where the vocal cords spasm and cause suffocation. It's sphincter-tightening for even the most seasoned physician to witness as it requires immediate and aggressive medical intervention to prevent cardiac arrest. Thankfully it only occurs in roughly 0.4 percent of cases, but this fact alone should strike fear in anyone considering using it without supervision from a medical professional.)