Final answer:
The effectiveness of Tegretol for treating trigeminal neuralgia is best indicated by a reduction in the frequency and severity of pain episodes. Other options related to heart rate, blood pressure, and blood glucose levels are not related to the medication's efficacy for this condition.
Step-by-step explanation:
To determine if Tegretol (carbamazepine), a medication used for treating trigeminal neuralgia, is working effectively, one would look for a reduction in the frequency and severity of pain episodes associated with the condition. Neither increased heart rate, decreased blood pressure, nor elevated blood glucose are directly related to the efficacy of Tegretol for this use. Instead, the best indicator of Tegretol's effectiveness for trigeminal neuralgia is c) Reduced pain episodes. This aligns with the medication's intent, which is to diminish nerve pain by stabilizing the nerve membranes and reducing the firing of the trigeminal nerve.