Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am so sorry to hear that Sunny is in so much pain, not controlled with Prednisone and Tramadol. That combination is often very helpful for dogs with intervertebral disc disease.
The short answer is that if those medications aren't helping enough we can add more medication to relieve discomfort.
If she is having painful muscle spasms then a muscle relaxant such as methocarbamol can be added, and Gabapentin can be used along with the medications she is taking as well.
Do not administer liquid formulations of Gabapentin intended for human use (such as Neurontin) to Sunny as these may contain high concentrations of xylitol. Xylitol is an artificial sweetener that is liver toxic in dogs.
The dose of Gabapentin for pain control in dogs is 1.5 to 3mgs per pound of body weight once daily. A 40 pound dog could take 60- 120mgs per day. We recommend starting with the low end in dogs that are taking other drugs that are in the morphine family (tramadol). Side effects are possible sedation and incoordination.
At home now you can alternate warm and cold compresses on her neck muscles for 10 minutes at a time several times a day. The warmth relieves painful muscle spasms and the cold helps decrease inflammation. At this point, this many days out, I suspect she will benefit most from warm compresses.
She should be closely confined starting now. No stairs, running or jumping. If you have a crate for her I highly recommend using it. The less she moves around the more comfortable she will be and the faster she will heal.
She should go out on a leash to relieve herself. Do not use a collar for her, a harness which more evenly distributes forces if she pulls on her leash is better. You will need to confine her for several weeks, even as she starts to feel better or she may reinjure herself. Keeping her on the thin side is recommended to decrease stress on her neck and back, but is no guarantee that she won't have another episode. Once a dog has one bad disc the likelihood of another is very high.
In some cases we cannot control pain with medication and surgery becomes the only possible option. I think it is worth adding medication, but I wanted you to be aware of that.
If you are interested in reading more here is a link to an excellent article about intervertebral disc disease, its causes and therapy: http://www.petwave.com/Dogs/Dog-Health-Center/Bone-Joint-Muscle-Disorders/Intervertebral-Disk-Disease/Symptoms.aspx
There are other less common causes of back pain such as infections, tumors of the vertebrae or the spinal cord itself or fibrocartilagenous emboli but far and away disc disease is the most common cause of back pain in dogs.
Please let me know if you have any further questions.