I get a nasty reaction to novocaine when combined, as is the usual practice in the US, with epinephrine (also known as adrenaline.) Epinephrine can make you shake. In me, it causes violent nausea. Dentists use it because it contracts the blood vessels and the novocaine lasts longer.
I ask for novocaine WITHOUT epinephrine and that really makes a big difference.
There is significant PAIN, sharp like someone is driving a knitting needle up through the room of my mouth and into my brain, with the initial injection, which previous dentists always dismiss, but for me it is severe. My current dentist, who I have had for about 10 years, has a son with developmental disabilities. He takes care to give the injections slowly and in areas known to be less reactive. I don't hurt when he injects the novocaine.
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The river is the melody
And sky is the refrain - Gordon Lightfoot