Several other medicines like pregabalin, gabapentin, amitriptyline, fluoxetine, escitalopram, nortryptilline and several combinations of the above are available. We don't know which medicine will give optimal relief for any given patient because of patient to patient difference in drug metabolism and response. What we call as pharmacokinetic and pharmacodynamic heterogeneity. Hence we can arrive at the optimal treatment in any given case only after trying out one drug at a time under strict medical supervision and evaluation.