I awoke from my sleep last night and was stretching my legs. I believe that I clenched my toes, flexed my ankle, and then flexed my knee. My gastroc contracted incredibly tightly, causing excruciating pain, and I was completely unable to move my leg from knee down. I was in so much pain that it took at least 30 seconds to explain to my boyfriend what was happening. He proceeded to manually extend my gastroc, relieving the acute pain. However, the pain was intense enough that I vomited after cessation, and had a low grade fever for 20-30 minutes. My leg is pretty sore today.
I have a history of sciatica (I'm a runner), mild herpes zoster, and mild carpal tunnel pain. Also, I started Chantix for smoking cessation 2 days prior. I have taken Chantix in the past, and tolerated it well with the exception of constipation. Pfizer does not list anything like this as a previously observed Chantix side effect.