The
incidence of myoclonus (muscle twitching or spasm) in patients on high doses of morphine appeared to be increased by tricyclic antidepressants in one study. Some studies suggest that the concurrent use of
opioids and
tricyclics may result in raised drug levels (amitriptyline and clomipramine increased the AUC of morphine, dextropropoxyphene (propoxyphene) raised amitriptyline and doxepin levels, and methadone raised desipramine levels). There is some evidence that suggests that combined use of
opioids and
tricyclics makes patients drowsier, clumsier and therefore more accident-prone, and may increase the risk of respiratory depression.
Serious adverse interactions seem rare. An increase in opioid levels could be
O beneficial,butbeawarethatincreasedadverseeffectsareapossibility.Bealertfor
any evidence of increased
CNS depression and increased tricyclic antidepressant adverse effects. Warn patients that sedation can occur. Respiratory depression is more likely to be of significance in those who already have respiratory impairment. Note that some
tricyclics and high-dose methadone may prolong the QT interval, see drugs that prolong the QT interval.