20? damn. Owch!.
As for constipation, that is one side effect of opiates and opioids (the difference, if you wondered, is that opiates are those derived from the poppy plant, whilst all others, strictly speaking are known as opioids), that despite the way tolerance can skyrocket with ever increasing doses etc., there seems to be very little tolerance developed to the way they tend to slow peristalsis and gastric emptying etc.)
That, and itching, for those who get a lot of histamine release (some opioids/opiates are worse than others for causing itching however. For example, fentanyl, in me, although I really dislike the stuff, it causes relatively little constipation and almost no itching. Codeine, causes a ton of itching, and especially terrible for it, is morphine, an IM or subcutaneous morphine shot, or IV dose causes MASSES of itching, and if I were to inject it IV, and have just a very little bit of the solution miss the vein and go into the tissues around it instead, then I'll get non-painful, but damn itchy hives, spreading up the limb used, which blanches and turns pale, with raised, coin-sized welts that itch like crazy. Although they don't last very long. I've been taking it for quite a long time now, and I've developed tolerance, being a chronic pain patient on significant doses of morphine and oxycodone, but whilst tolerance to respiratory depression occurs quite fast, likewise it also does to euphoria, effects that could be considered recreational, whether the dose taken was taken for that reason or otherwise, tolerance to this takes place quickly, but even over the years, there is little or no tolerance either to the histamine releasing effects, or to constipation.
Although as mentioned some cause worse histamine release than others. Morphine, as I said, does it a lot. Dipropionylmorphine, heroin, do it less so than morphine, quite considerably, particularly dipropionylmorphine. Methadone almost completely lacks such effects in me, and oxycodone, slightly more than methadone but not very much at all.
