I know this drug very well. I was on it for several years for depression. At one point, I was taking 600 mg a day.I wasn't aware that imipramine was given for pain, though I suppose that any of the trycyclics could be used for pain. The two trycyclics that seem to be most often used for pain are Pamelor (nortryptiline) and desipramine (I don't know the brand name). Both of these can cause tachycardia. I suppose that it's possible that imipramine can do this too, but I think that the tachycardia is due to these drugs' effect on epinephrine. Imipramine isn't supposed to have such a marked effect; I may be wrong about this. I have had problems with rapid heart beat (tachycardia) on desipramine and nortryptiline. I never had this kind of problem, even on massive dosses of imipramine. All the trycyclics can effect blood pressure.You have to keep in mind that you are on really, really small doses of these medications. For example, I am now taking 25mg 2x a day of nortryptiline. That is considered to be a small dose also.Steven