Prochlorperazine and Cardiovascular disease

Phenothiazines may cause hypotension (including orthostatic hypotension), reflex tachycardia, increased pulse rate, syncope, and dizziness, particularly after the first parenteral dose but rarely after the first oral dose. Low-potency agents such as chlorpromazine and thioridazine are more likely to induce these effects, which usually subside within the first couple of hours following administration. Tolerance to the hypotensive effects often develops after a few doses. Rarely, fatal cardiac arrest has occurred secondary to severe hypotension. Other reported adverse cardiovascular effects include edema, thrombosis, and ECG abnormalities such as PR and QT interval prolongation, diffuse T-wave flattening, and ST segment depression. Therapy with phenothiazines should be avoided or otherwise administered cautiously in patients with severe cardiovascular disease, pheochromocytoma, a predisposition to hypotension, or conditions that could be exacerbated by hypotension such as a history of myocardial infarction, angina, or ischemic stroke. Close monitoring of cardiovascular status, including ECG changes, is recommended at all dosages. If parenteral therapy is given, patients should be in a supine position during administration and for at least 30 to 60 minutes afterwards. Patients who experience orthostatic hypotension should be cautioned not to rise too abruptly. Occasionally, when severe, hypotension may require treatment with vasoconstrictive agents such as norepinephrine or phenylephrine. Epinephrine should not be used, however, since phenothiazines can reverse its vasopressor effects and cause a further lowering of blood pressure.