"It belongs to the piperazine class of phenothiazines and is extremely potent; more potent than haloperidol and around fifty to seventy times the potency of chlorpromazine."
While fluphenazine certainly is a highly potent neuroleptic, I don't think it's more potent than haloperidol. Most sources I have state, that the neuroleptic potency of fluphenazine dihydrochloride administred orally or intramusculary is somewhere between 30 and 40 (maximum 50) chlorpromazine-equivalents; haloperidol is stated to have CPZeq. of 50 in all sources I have to my disposition; thus, fluphenazine is slightly less, or maximaly equaly potent, compared to haloperidol; in one publication, intramuscular fluphenazine decanoate is stated to have a potency of about 115 - 130 CPZeq's, but then again, haloperidol decanoate . is stated to have potency of 110 - 125 CPZeq.-- 00:12, 1 May 2007 (UTC)
Decanoic acid acts as a non-competitive AMPA receptor antagonist at therapeutically relevant concentrations, in a voltage- and subunit-dependent manner, and this is sufficient to explain its antiseizure effects.  This direct inhibition of excitatory neurotransmission by decanoic acid in the brain contributes to the anticonvulsant effect of the MCT ketogenic diet .  Decanoic acid and the AMPA receptor antagonist drug perampanel act at separate sites on the AMPA receptor, and so it is possible that they have a cooperative effect at the AMPA receptor, suggesting that perampanel and the ketogenic diet could be synergistic. 
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.