It should not be used concomitantly with medications known to prolong the QTc interval (. 5-HT3 antagonists , tricyclic antidepressants , citalopram , etc.) as this may lead to an increased risk of QTc interval prolongation.   Neither should it be given concurrently with lithium (medication) as it may increase the risk of lithium toxicity and neuroleptic malignant syndrome .    It should not be given concurrently with other antipsychotics due to the potential for this to increase the risk of side effects, especially neurological side effects such as neuroleptic malignant syndrome .    It should be avoided in patients on CNS depressants such as opioids, alcohol and barbiturates. 
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. 
Fluphenazine is contraindicated in patients with hematological disease. Hematologic effects including leukopenia, neutropenia, and agranulocytosis have been associated with antipsychotic use. A history of drug-induced leukopenia or neutropenia or pre-existing low white blood cell (WBC) count may increase the likelihood of developing hematologic effects during treatment with an antipsychotic medication. Patients with a history of clinically significant low WBC count or drug-induced leukopenia/neutropenia should have frequent complete blood count (CBC) assessments during the first few months of treatment. Discontinuation of the antipsychotic should be considered if a clinically significant decline in WBC occurs in the absence of an identifiable cause. Patients with clinically significant neutropenia should be closely monitored for fever and infection, and appropriate medical intervention should be instituted if necessary. Fluphenazine should be discontinued in patients with severe neutropenia (ANC < 1000/mm3); ongoing medical care is recommended until the symptoms resolve. Patients with bone marrow suppression secondary to phenothiazine use should not be re-exposed to phenothiazine treatment.