Final answer:
Ergot drugs, including Methergine, are contraindicated in hypertensive patients due to their vasoconstrictive effects which can worsen hypertension and lead to critical complications.
Step-by-step explanation:
Ergot drugs such as Methergine are contraindicated in patients with hypertension because they can cause a further increase in blood pressure. Ergot derivatives can constrict blood vessels, which is not advisable in a hypertensive patient as it can exacerbate the condition and lead to severe complications like stroke. These drugs work on alpha-adrenergic, serotonergic, and dopaminergic receptors, arousing vasoconstriction, which is dangerous in the setting of already elevated blood pressure.