Hi, I had asked couple of questions earlier and I have waited for you, but it is possible you are currently not in a position to reply to me, what I will do is provide you an initial answer and explain how the very bad and worsening PHN can be treated successfully, after going through this answer if you have any further questions or need any further clarifications then please follow up with me and we can discuss this further.
Coming to the discussion;
Sorry to see you are suffering from very bad PHN and also the symptoms are worsening too but please see that the PHN is not a permanent condition, the neuralgia symptoms will subside eventually, sadly it is taking a prolonged course in your case but the symptoms will eventually subside. Until PHN subsides you will obviously require proper treatments to get relief from this very bad pain and I will discuss the various treatment options below here.
One of the options is to increase the dose of gabapentin further. I see the current dose of gabapentin you are on is not helping you much for the pain, but it seems helping with RLS & sleep, but not for the pain from PHN. Please see that the dose of gabapentin can be raised further to see whether it will help. Some patients respond to higher doses of this med, so you may try to optimize the dose further. The highest dose PHN patients go on gabapentin is usually around 3600 mg/day (in divided doses), as per my estimation you appear to be currently on around 1500 mg/day (5 pills of 300 mg each, please correct me if I am wrong), if my estimation is correct then you may gradually up the dose further and see whether higher doses will help you as discussed above (if required up to total 3600 mg per day - taken in divided doses).
If you up the dose of gabapentin as above but it does not help you, or if you are already not in favour of optimizing the dose of gabapentin further for whatever reasons and want to explore other treatment options then I have posted below a list of various additional treatment options that are available for the management of PHN.
This is the list of various additional treatments to help with very severe pain from PHN;
1) One of the nerve-pain relieving pills like Carbamazepine, or Oxcarbazepine etc (these can also be combined with Gabapentin)
2) Opioid (Narcotic) pain killers like Lortab or Vicodin or Percocet etc
3) Nerve-irritation relieving skin creams/ointments, or skin patches like Capsaicin skin cream (Zostrix skin cream), Capsaicin skin patches (Qutenza), Lidoderm anesthetic skin patches, Lidoderm skin cream etc
4) Skin soothing agents like Calamine lotion or Calamine cream
5) CAM (Complementary and Alternative Medicine treatments) like Acupuncture
6) If these above interventions do not help then one of the special procedures like
Nerve blocks with anesthetic agents (with or without steroid), or Sectioning of the affected nerve etc can help.
I am not telling each & every patient will require each & every of the above mentioned treatments, I am just providing you with a list like this so that you are familiar with the various treatment options that are available to treat this torturesome pain condition from very bad PHN.
Please let me know if you have any further questions, or if you want to discuss this further; and please click a positive rating (preferably 5 Star/Excellent) to credit for the time & effort put by me in answering your health question, and this is the only way I will be credited for my service to you. If you have follow-up or additional questions you can ask them after the rating too.