Everyone responds to medication differently, including side effect profile.
If you are experience severe adverse effect from the medication, make sure you contact your physician right away. In addition, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online at: http://www.fda.gov/Safety/MedWatch or by phone:1-800-332-1088.
I am not sure what you mean by "numbness in the throat". Alprazolam is a muscle relaxant and may cause dysarthria, or a motor speech problem due to inability to use or control muscles of the mouth, tongue, larynx, or vocal chord. I'd recommend for you to consult your physician regarding your reaction to alprazolam.
Also, are you taking the extended release formulation? If you are, please "do not chew, crush, or break them".
Please note: there is a moderate drug interaction with alprazolam and metoclopramide. When taken together, there is an increase risk for side effects such as dizziness, drowsiness, and difficulty concentrating. Monitor them closely if you are taking them together.
For more information, please go to:
1. Alprazolam XR - Daily Med
2. Alprazolam - Medline Plus
3. Dysarthria - Medline Plus
I have been on very low-dose Xanax (usually 1/2 half of .25mg. on an as-needed basis) for about four years. I have never experienced numbness. Maybe your fear is getting the better of you. I find Xanax very helpful and it pays quit to a panic attack almost immediately.