It appears that your pain is due to diabetic neuropathy. Unfortunately, it is very difficult to cure this disorder but one can stop progression by effective control over blood sugar.
Gabaneuron is a brand name of a product that contains two medicines in a Fixed-Dose Combination (FDC): gabapentin 300 mg and methylcobalamin 500mcg. It is medically an irrational combination, not allowed to be manufactured in any advanced, western country such as US, Britain, Australia etc. Because of lax laws in India, such FDCs have flooded the market.
Even if a patient needs both gabapentin and methylcobalamin, these drugs should be taken individually.
Gabapentin is actually a drug meant for epilepsy but it also controls nerve pain. However it has no curative role. The moment one stops taking this drug, the pain returns. Hence as a pain-killer, gabapentin should only be taken for acute, severe pain. For little pain in the back of the shoulder it is not advisable to take this medicine. Furthermore it should be avoided in kidney impairment (a creatinine level of 1.5 mg/dL is a bit on the higher side) because of its adverse effects, not to mention the fact that there is along list of other side effects right from dizziness, unstable gait to pain in joints, diplopia (two images of the same article) etc. Surprisingly, one of the side effects of gabapentin is back pain!
For aches and pain, you should only take paracetamol (Crocin).
Methylcobalamin is claimed to control diabetic peripheral neuropathy. It should be taken as a single-ingredient (not combination) product such as Methycobal, (Wockhardt). The dose is 500mcg tablet 3 times daily for two months initially; if there is no improvement it should be stopped after 3 months.