Why didn't my xanax work this time ?

So lately my anxiety has calmed down a lot for the past few months but for some reason out of nowhere today I started getting anxiety. I assumed it would just last a few minutes and pass but it actually started getting worse and worse so I decided to take a xanax . I rarely ever take xanax maybe once a month for when I get horrible anxiety and don't want to have a panic attack. I only take .25 and I break the pill in half. So I only take half of a .25 pill as this is always enough to calm me down .
So after I took the xanax i patiently waited for it to work as I know it can take up to 45 minutes . For some reason the xanax didn't do anything and for the next 2 hours my anxiety was worse I even kept getting on and off mini panic attacks it was horrible I've never had my panic attacks go on and off I usually just have one big one and then I feel ok afterwards . I got even more scared that this was something else and not anxiety because the xanax didn't work and if it was anxiety wouldn't the xanax have to work ? I even got scared that maybe it was a heart attack because I've heard one of the symptoms can be anxiety and this worried me even more . This is the first time that my Xanax didn't have any effect on me. What does this mean ?

Hi Brandi
Sorry anxiety has flared ... Its only a blip your rational mind knows it but the anxiety head is telling you other wise.
If it happens again take another quarter that's still only 1 mg which is under the normal dose add some coping skills anything you know works for you.

You seem to have thing's sussed as you've been doing so well so keep it up.
As for the tiny amount not working you probably had more anxiety than was showing and just needed that little bit extra .

Your not on your own , I was given some for emergency situation s and split my 2mg tabs into same as you and once in a taxi to airport quarter wasn't enough so had to have another ....
Which was still way under prescribed dose... So try not to worry about it is possible.

They are still in my drawer but thankfully have not needed them since...

Strength and encouragement to you