Known to cause QT prolongation, ex. ondansetron (Zofran), granisetron (Kytril), and dolasetron (Anzemet). These drugs have been reported to widen the QRS complex and prolong JT, QT, and PR intervals. Dolasetron (-4mg/kg IV) can prolong QRS by 5-20% whereas Ondansetron has been shown to increase QT and JT intervals by an average of 2-5%. The QRS widening is likely due to blockade of sodium channels while the QT prolongation is caused by blocking potassium channels. In a study done with human myocytes, all of the drugs in this class where shown to block human cardiac Na+ channels probably by interacting with the inactivated state. This could lead to clinically relevant blockade, especially with high heart rates or depolarized/ischemic tissue, potentially leading to ventricular arrhythmias. The rank order of potency for Na+ blockade is granisetron>dolasetron>ondansetron. For blockade of the K+ channel (QT prolongation), the order of potency is ondansetron>granisetron>dolasetron.
There are no well controlled studies with Haldol (haloperidol) in pregnant women. There are reports, however, of cases of limb malformations observed following maternal use of Haldol along with other drugs which have suspected teratogenic potential during the first trimester of pregnancy. Causal relationships were not established in these cases. Since such experience does not exclude the possibility of fetal damage due to Haldol, this drug should be used during pregnancy or in women likely to become pregnant only if the benefit clearly justifies a potential risk to the fetus.