I found it! You can find a lot about this on Google, just type in the words "Stop with Effexor".

Here is what I found so far:

What happens when I stop using EFFEXOR XR?
Symptoms are known to occur when people stop using EFFEXOR XR, especially when they suddenly stop therapy.

When people suddenly stop using EFFEXOR XR, they can get symptoms from stopping the medicine too fast. Some of these symptoms include:

Agitation
Anxiety
Confusion
Diarrhea
Dizziness or vertigo
Dry mouth
Fasciculation (muscle twitching)
Headaches
Hypomania
Impaired coordination
Insomnia (trouble sleeping)
Loss of appetite
Nausea
Nervousness
Nightmares
Seizures
Sensory disturbances (including electric shock sensations)
Somnolence (sleepiness)
Sweating
Tinnitus
Tiredness
Tremor
Unpleasant mood
Vomiting

Do not stop taking EFFEXOR XR without talking with your doctor first. Your doctor may want to slowly decrease your dose of EFFEXOR XR to help avoid these kinds of symptoms.Stop as slowly as possible.