Very Little Change After Botox on Forehead

Normally at this point, most patients would see noticeable results after a Botox treatment. If you can still raise your eyebrows, then you may possibly be able to have more Botox injected to help soften those lines. If the lines are present, but you are not able to raise your eyebrows at all, then more Botox will not improve your result - it may actually cause ptosis. Botox does not always eradicate lines. It can soften them and prevent them from worsening over time with repeated treatments. It is best to consult with the person who performed your injections to be evaluated in order to determine the right course of action for you. 

Botox works by irreversibly inhibiting Acetylcholine release at the neural synapse. It takes 3-5 days for the remaining Acetylcholine stores to be used up, and as they are used up, the Botox will take effect. Waiting additional days will not enhance the results.
If you feel that you did not see results, have a frank discussion with your plastic surgeon about the administered Botox and determine if you need additional units of the Botulinum toxin.

Dear Annie,
As the post above attest, there could be MANY reasons why your Botox treatment may have been a disappointment to you.
By 12 days you would have seen a complete effect of the Botox. So - the period of elapsed time is not the answer.
Nor do I believe that your surgeon would have partially treated your frontalis muscles generated wrinkles without telling you as some of the above posts was suggesting. Yes -- weakening the frontalis in people who need it to prevent upper eyelid skin from dropping lower is counterindicated BUT a surgeon would tell you why they chose not to treat those folds rather than allowing you to believe they did.
Botox is most effective in smoothing active wrinkles - the wrinkles that appear on facial animation. You plainly state that "the lines were already visible at rest". The likelihood of Botox erasing established lines is very low. To do so would require Botox AND a filler (Restylane/Perlane OR Juvederm).
Botox efficacy depends on how it was reconstituted (gently or allowed to bubble which reduces its potency), was it over diluted (ie you are getting less Botox units than you should) and was it old and less potent. Always possible when a surgeon is not busy and reconstituted Botox sits in his/her fridge.
Lastly, Botox injectors are NOT the same. Some surgeons are better at doing it than others. Witness if you will the plethora of freakish botoxed celebrities with the "Spock look" (depression of the medial brow with unnatural elevation of the lateral brow). I am sure they paid a lot for their treatments -- but such Botox results are far from optimal.
Hope that helped.

If you have had forehead lines for a while, it will take a while to soften them up. Of course, Botox is designed to treat the underlying muscles that cause the wrinkles, but it does not actually change the skin. So, after the muscles are paralyzed, and done so on a continuous basis (meaning you have to keep up with re-treatments), eventually the wrinkles should soften up.
Sun damage, smoking, etc. can damage the skin and work to increase wrinkling. Protecting the skin, exfoliation and hydration will help treat the skin while the Botox works on the muscles that contract and can accentuate the folds (wrinkles) that are more likely to appear in damaged, as opposed to healthy skin.
Also, people require different doses of Botox. Some people need minimal units injected. Others need more. It sometimes takes a session or two or your doctor to figure out what dose works best in your case.

Annie,
It may take a few treatments of Botox to eventually smooth your forehead.  Look in the mirror and try to raise your eyebrows.  If you are unable to raise them, then your Botox is working.  Patience.

Your doctor did nothing wrong, nor is Botox not being effective. If you give high doses to the forehead, the brows will drop. We often need additional treatments to improve lines that are not just from facial muscle movement, but from sun damage too. Laser and filler are two complementing treatments to Botox in this area. Go see your doctor to discuss the options.

Botox does not treat wrinkles, it treats the muscles that make them. Therefore one should not expect prominent horizontal lines of the forehead to go away after one injection. Be patient, with continued ,regular use of Botox, the lines should soften because the muscles that created them have been weakened.

botox for the horizontal lines on the forehead is tricky. If you put too much in you drop the eyebrows and create a heavy upper lid. Put too little in and you don't get an effect. I would recommend going back to the doctor and getting a little more Botox. If you don't respond to more Botox you may be someone who has Botox anti-bodies and Botox does not work for you.

Botox works well for dynamic lines and usually will help within 2 weeks.  Lines that are present at rest may take months to remodel and may take up to 3 cycles of Botox over a year to remodel and smooth out,

There could be many explanations. In my mind, the practical issue is to get good results next time you have Botox.Ask your doctor to administer freshly prepared botox in sufficient concentration. If the forehead has many strong lines, you might need 25-40 units to get a complete correction. Best of luck!