Which tcas is more potent for sciatica pain relief, amitriptyline (or nortriptyline), imipramine (or desipramine)?

TCA. Tca are classic for neuropathic pain - sciatica for example. Any of the ones u mentioned may be quite eefective - and cheap. They are not without side effects - dry mouth, constipation, sedation. Any of the ones u mentioned can be effective. I personally like amytryptilline - 10mg at night - as mentioned all will work. Additionally other meds such as lyrica, (pregabalin) neurontin, Cymbalta are options.
Hard to say. generally though nortriptyline seems to have less side effects than the others.