I have been experiencing horrible anxiety and panic attacks since I was injected 4 weeks ago, read online this is very common.

I’m sorry to hear you are having anxiety problems. I’m also sorry  to repeat what other Drs have told you. The Botox has nothing to do with your anxiety issue. You need to see a Dr who specializes in treating anxiety disorders.

Your Botox is bound to the receptor in the muscle nerve junction where it was injected. It is not floating around in your body. Since your primary doctor's attempt to treat your anxiety did not work, I strongly suggest you see a psychiatrist for a formal consultation to take control of your anxiety symptoms. Botox is one of the safest medications around and has been injected millions of times into humans with an excellent track record. 

I have been injecting Botox for over 10 years in a very high-volume cosmetic practice and have not heard of any patient complain about Botox causing anxiety. To reassure you, the anxiety is real and can be appropriatley treated. However regardless what others say online it is NOT related to Botox. I believe you will have a hard time finding an authority or experiened physician to tell you otherwise.
That is not to say the things you are reading aren't honest people simply telling THEIR truth of what they BELIEVE to be the cause. However, anxiety is common and many people often attribute symptoms to something that seems to makes sense to them, especially if the timing is consistent with onset of their symptoms.
Personnally I have experienced anxiety and know first hand that it can be quite disturbing and disabling- often leading to more anxiety! There are several treatment options that are helpful if done in combination:
1. Short term anxiety med - oftentimes first med will not work (Buspar not great for significant anxiety) - so be patient and go back to same MD for another med if warranted.
2. Any exercise is good and daily WALKING by far is the best for me.
3. TALKING is helpful - so don't isolate!  Share your symptoms and feelings with trusted friends, family or counselor.
Hope you feel better soon. Let us know how things turn out.

Hi there -
This is a tough one. 
Botulinum toxin has been used for many years for medical conditions such as strabismus and spasticity with an excellent safety profile. 
However there have been a very few number of reported issues as it has become more commonly used.
When injected in high medical doses for conditions such as muscle spasticity, botulinum toxin can extremely rarely enter the systemic circulation in doses high enough to cause muscle weakness. The cases seen were seen mostly when botulinum doses were over 600 units and injected into large vascular muscles (so higher number of blood vessels able to carry the toxin throughout the body) 
These doses were MUCH MUCH larger than any cosmetic injections.
Also the side effects from such large doses were muscle weakness - not anxiety.  
When we inject even small doses for cosmetic use, there is a chance that the tiny capillaries in the skin and facial muscles could carry minute doses into the systemic circulation. Looking at the medical studies though, it really appears the cosmetic doses would be too low to cause weakness of muscles and would be undetectable to the patient. 
That being said, I have seen forums where people have described unusual symptoms after cosmetic botulinum injections which don't make any logical sense knowing what we know from its current safety profile.
Who knows what time will tell.
I would advise you to report your symptoms  to Allergan, the makers of Botox, at 1 (800) 433-8871. 
If there really were a syndrome, then the only way it could be confirmed, would be if it were reported repeatedly and studied. 
All of this, of course, doesn't help you right now.
Whatever is causing your symptoms is causing you a great deal of distress. Even if Botox were the culprit there is no reversal agent. The rare cases showing musculature weakness in patients receiving over 600 units resolved within 3 months. 
I would agree with the other  physicians.
Please see a psychiatrist as they have a larger selection of anxiety medications to draw from - hopefully one will help you.
I wish you all the luck and take care.

Botox is not causing your anxiety. Botox is bound to the neuromuscular junction in the muscle it was injected causing it to relax. Your anxiety is caused because you believe it is causing you harm. You have anxiety and panic attacks that were triggered by Botox injections, but not caused by the Botox itself. Ask your family and friends if you were more anxious than the average person before the Botox was ever given. You should see a psychiatrist/psychologist to help with this as it is unlikely to fully resolve even after the Botox completely wears off in a few months.