The intravenous route is not FDA approved and is generally not recommended except when no other alternatives are available. Intravenous administration appears to be associated with a higher risk of QT prolongation and torsade de pointes (TdP) than other forms of administration. The manufacturer recommends ECG monitoring for QT prolongation and arrhythmias if IV administration is required. A dose in the range of 1 to 5 mg IV has been suggested, with the dose being repeated at 30 to 60 minute intervals, if needed. A maximum IV dose has not been established. The lowest effective dose should be used in conjunction with conversion to oral therapy as soon as possible.
The good news is that, even with these medications, most patients do not have significant weight gain . People who are going to gain a significant amount of weight typically report a sudden (within a day or two) fairly dramatic increase in carbohydrate craving (raiding the refrigerator at night for ice cream or other high carbohydrate foods). Thus, if there is a good reason to try one of these medications, it is reasonable to do so and closely monitor for weight gain. If there is no significant change in appetite or weight in the first two weeks of treatment the risks of significant weight gain over time are much reduced.