I have this same thing happen, and for what I know it is the thyroid dumping hormones. The thyroid is in that area of the throat and drips the hormones you need, but sometimes if you have a sluggish (Hypothyroid) or overactive (Hyperthyroid) it can suddenly dump a large amount of hormones all at once. It tastes very bitter, and in my experience its bitter, medical, and oily tasting.
You may want to get a blood test to check for either condition.