Its effects on the ECG include prolongation of the PR and QT intervals, blunting of the T wave and depression of the S-T segment. Ventricular arrythmia and sudden death have occurred rarely. Orthostatic hypotension is common after parenteral administration and usually lasts one-half to 2 hours. Patients should be supine when parenteral chlorpromazine is administered. Tachycardia, fainting and dizziness have also occurred.
Hypotension can also occur after oral administration.
Tolerance to hypotensive effects generally develop over time, however hypotension can persist in some patients, especially the elderly. In addition, slowing of the EEG rhythm, disturbed body temperature and lowering of the convulsive threshold have occurred. Dizziness has been reported. Tardive dyskinesia may appear in some patients on long term antipsychotic therapy or may appear after drug therapy has been discontinued. The risk appears to be greater in elderly patients on high-dose therapy, especially females.