The benefits from the first shot only lasted 2 weeks. The second and third set of injections lasted about 90 days. In November, I was ready to have surgery. My EMG and nerve conduction tests proved that the nerves were "sleeping" before I was. After another MRI, the neurosurgeon said I was a candidate for surgery but I was not able to get the endoscopic type surgery that is less invasive. I would have an incision about 6-8" long. Along with removing the herniation, they would have to increase the size of the hole where the nerve roots were going through.
Activated charcoal can act as an adsorbent (kind of a "chemical sponge") to bind toxins in the gut. If you use a preparation that is safe for people and use a smaller dose, it should be harmless.
If the problem was an insect sting, I doubt that there are any toxins in the gut that the charcoal would help with.
So many times we are unable to determine the source of the allergen.
Kenalog is a long-acting corticosteroid (cortisone) injection that stays in the body for weeks, where the dexamethasone lasts only a couple of days.
Antihistamines like benadryl are often helpful for something like an insect sting, even though most dogs don't get much relief from them in regard to allergic itching.