Annals of the American Psychotherapy Association - The conventional long-acting antipsychotics
In the last primer, we discussed the first long-acting formulation of an atypical antipsychotic, Risperdal Consta, which became available in 2003. For the sake of completeness regarding this primer, it should be noted that long-acting forms of two conventional antipsychotics were developed in the 1960s, namely fluphenazine (Prolixin) decanoate and haloperidol (Haldol) decanoate. They have a risk versus benefit profile less favorable than the atypical antipsychotics (1) but have assisted with compliance and subsequently decreased both relapse rates and re-hospitalizations in comparison to oral neuroleptics over extended periods of time. (2)
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Haldol decanoate is administered intramuscularly and results in a slow and sustained release of haloperidol. The indications and target symptoms are similar to those for oral Haldol, but the duration of action is longer. Haloperidol decanoate reaches a peak at about 6 days and has an apparent half-life of about 3 weeks. Steady state plasma concentrations are achieved after the third or fourth dose. It is indicated for the treatment of patients who have schizophrenia and require prolonged parenteral antipsychotic therapy. It blocks the effects of dopamine and increases its turnover rate; (3) however, the exact mechanism of action is unknown.
It is available in two doses: 50 and 100 milligrams (mg). Patients should be tried on the oral formulation to establish tolerability and response. The initial decanoate dose is 10-20 times the previous daily oral dose; however, the elderly, debilitated, or those maintained on low doses may need lower doses and a conversion factor of 10-15 times the previous oral dose. Regardless of the conversion, the first dose should not exceed 100 mg. If the conversion requires more than 100 mg, then it should be administered in 2 injections, with a maximum of 100 mg in the first shot followed by the remaining in 3-7 days. It is usually administered every 4 weeks (monthly), but patient response may warrant a more frequent dosing interval. Clinical experience at doses greater than 450 mg a month has been limited. (3)
Fluphenazine decanoate is available for both intramuscular and subcutaneous administration. The onset of action is between 24 and 72 hours after injection and the effect on psychosis becomes significant within 48-96 hours. Like haloperidol decanoate, it is intended for the management of patients with schizophrenia who require prolonged parenteral neuroleptic treatment, but the exact mechanism of action is unknown.
Patients should be started on a short-acting formulation of fluphenazine to determine dose and response. A 10 mg daily dose of oral fluphenazine conforms approximately to 12.5 mg of fluphenazine decanoate every 3 weeks. For most patients a dose of 12.5 mg or 25 mg may be given to initiate therapy. Subsequent injections and the dosage interval are determined in accordance with the patient’s response. If doses greater than 50 mg are deemed necessary, the next dose and succeeding doses should be increased cautiously in increments of 12.5 mg. Dosage should not exceed 100 mg. (4)
Both haloperidol decanoate and fluphenazine decanoate can cause the following adverse effects: sedation, hyperprolactinemia, extrapyramidal symptoms, tardive dyskinesia, neuroleptic malignant syndrome, and acute dystonic reactions. These preparations are esterified in a sesame oil vehicle, so both acute and cumulative local reactions at the injection site are possible. As with other antipsychotic agents it should be noted that they can potentiate central nervous system depressants such as anesthetics, opiates, and alcohol. They are contraindicated in comatose states and known hypersentivity. Haloperidol decanoate is classified as category “C” in pregnancy; there is no current evidence of fetal damage. Fluphenazine decanoate is not intended for use in children under 12 years of age, and its safety in pregnancy has not been established. Cardiac effects of Haldol may include prolongation of the QT segment on the electrocardiogram and changes compatible with the polymorphous shapes of torsades de pointes. (3,4)
A risk-benefit assessment with long-term depot antipsychotics showed that the main advantage was in overcoming noncompliance. Further, it reduced the individual variation in bioavailability, metabolism, and maintained stable plasma concentrations over long periods. (5) A pharmaco-economic model showed considerable cost savings with haloperidol decanoate versus oral Haldol or oral Risperdal. (6)
CME/CREDIT
CE/CREDIT
This 1-credit continuing education opportunity is co-sponsored by the American College of Forensic Examiners International (ACFEI) and the American Psychotherapy Association. ACFEI maintains responsibility For all continuing education accreditations. This article is approved by the following for 1 continuing education credit:
APA provides this continuing education credit for Diplomates.
This program is co-sponsored by ACFEI and APA. ACFEI is approved by the American Psychological Association to offer continuing education for psychologists. ACFEI maintains responsibility for the program.
