Involuntary movement: Like other medications to control symptoms of schizophrenia, fluphenazine decanoate may cause rhythmic involuntary movements, known as tardive dyskinesia . Tardive dyskinesia is more likely to occur in women and seniors. These movements may involve only the tongue, face, mouth, or jaw, or they may include the extremities and trunk. Tardive dyskinesia is not reversible for some people. Report involuntary movements including sticking out the tongue, puckering mouth, or chewing movements to your doctor as soon as possible.
Fluphenazine came into use in 1959.  The injectable form is on the World Health Organization's List of Essential Medicines , the most effective and safe medicines needed in a health system .  It is available as a generic medication .  In the United States the tablets costs between and USD per day for a typical dose.  The wholesale cost in the developing world of the long acting form is between and USD per injection as of 2014.  It was discontinued in Australia around mid 2017. 
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.