Final answer:
The combined use of methylergonovine and heavy smoking, which both cause vasoconstriction, can increase the risk of severe vasoconstriction in patients.
Step-by-step explanation:
The question pertains to the effects of methylergonovine, a medication used to control bleeding by contracting the uterus, particularly after childbirth. One of the known effects of methylergonovine is vasoconstriction. When combined with the effects of heavy smoking, which can also induce vasoconstriction due to nicotine, there is an increased risk for severe vasoconstriction. This can lead to complications, as both methylergonovine and nicotine have sympathomimetic properties that could exacerbate vasoconstrictive responses. It’s important to monitor patients receiving methylergonovine who are heavy smokers carefully for signs of excessive vasoconstriction and related complications.