Chronic use of morphine and other opioids is marked by acquired tolerance to the depressant agonist effects, e.g. analgesic action and respiratory depression (the fatal dose becomes higher), but not to some stimulant agonist effects, e.g. constipation and miosis, which persist.
Opioids that have mixed agonist/antagonist actions (partial agonists) induce tolerance to the agonist but not to the antagonist effects; naloxone (a pure antagonist) induces no tolerance to itself. There is a cross-tolerance between opioids (for dependence and withdrawal see below).
Acquired tolerance develops over days with continued frequent use and passes off (variably for different actions) over a few days to weeks.
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Did you ever think feeling angry and irritable could be a symptom of constipation? A horrible fullness and pressing sharp pains against the bladders can’t help but affect your mood. Sometimes you just want everyone to leave you alone and sleep to escape the pain. It is virtually impossible to be constipated and keep a sunny disposition. Follow the steps in this guide to alleviate constipation and lead a happier healthy life.