You should be careful when using this drug. One of the reasons some of the more severe side effects often occur is because of abuse of this medication, or of accidental misuse.
Remember to never take more than you need, or more than is recommended by your psychiatrist or a doctor. Furthermore, never mix this drug with alcohol, illegal drugs, or the wrong medications.
Do not use it with other sedative drugs and be careful about using cold medicines and additional muscle relaxers with it. There are also a long list of drugs such as antidepressants, MAOIs, and other psychotropic drugs you should not use with Alprazolam.
For a more comprehensive explanation of these dangers, talk to your medical doctor or psychiatrist. You can also view the other sections of this site.
If you are already having trouble breathing, feel like you are going to faint, or someone you know has just passed out call for medical help immediately. Otherwise, you could end up in a coma or even dead.
If it is not after hours and you have not yet experienced a reaction to the accidental or intentional overdose, still call for help right away. However, in this case you can ask for help from a non-emergency medical person in the event you can stop the bad reaction before it starts.
Either that or call the poison center. Usually they may tell you to take precautions such as drink water frequently to help flush out your system. Remember though that the method for preventing severe reactions to an overdose might be different for everyone.
The most important point to remember is to just make sure that you are safe. Make sure you get help immediately whether you are noticing the effects of an overdose or not.
You may not need to worry, though if you just accidentally took one too many pills and several hours already passed. In this case you are likely to not have anything to worry about.