Suggest Treatment For Peripheral Neuropathy
SNRI class is the one option left.
Detailed Answer:
I read your question carefully and I understand your concern. Neuropathic symptoms can be very hard to treat at times.
I must say that looking at the tried medications the most common first choices seem to have been correctly applied. Unfortunately they don't always provide the hoped for relief.
Considering what other options you have, I would say there remains a group of antidepressants called SNRI which include either duloxetine or venlafaxine. They are also first line treatments for neuropathic pain and have the advantage of having much fewer side effects then amitriptyline which is not very appropriate at your age.
Also they can be tried in combination with gabapentin, some studies have shown combined therapy with venlafaxine and gabapentine to be better then either drug alone (although the added side effects should be kept in mind).
You seem to be already using other 2nd line options such as anesthetic cream and opioids (codeine).
Of course, if a cause could be determined (25% of cases can't be found) it should be treated. I'm assuming you've had other tests apart from those for diabetes and electrolytes (sodium) to determine the cause, like vitamin B12 deficiency, thyroid function etc.
I remain at your disposal for further questions.
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Detailed Answer:
I didn't mean in the sense of there being some interactions by the use of both drugs at the same time, actually there are no interactions between the two.
I meant it in the sense of being cautious of taking many drugs, in our case drugs which act on the nervous system (including alprazolam and codeine)
Common side effects for venlafaxine are headache, nausea, tiredness etc, while for gabapentin dizziness, balance issues (did your balance issues start after starting gabapentin?) drowsiness, somnolence, headache etc.
The dosage of Gabapentin you are taking is fairly low, it often is given 900mg a day or higher, I guess your doctor is being careful considering your age. If you have felt no side effects after starting it and have no kidney problems, perhaps you can discuss with your doctor increasing the dose before considering the therapy unsuccessful.
I hope to have been of help.