Penfluridol: an open phase III study in acute newly admitted hospitalized schizophrenic patients

Penfluridol for schizophrenia

BACKGROUND

Penfluridol, available since 1970, is an unusual long acting oral antipsychotic agent for the treatment of schizophrenia. It may be considered a depot medication as it is administered once a week.

OBJECTIVES

To review the effects of penfluridol for treatment of those with schizophrenia and schizophrenia-like illnesses in comparison to placebo, other antipsychotic medication or no intervention.

SEARCH STRATEGY

We undertook electronic searches of the Cochrane Schizophrenia Group's Register (2005), the Cochrane Central Register of Controlled Trials (2003-5) and LILACS (1982-2005). We hand searched references of all identified studies and sought citations of these studies in the Science Citation Index. We contacted the authors of trials and the manufacturer of penfluridol.

SELECTION CRITERIA

We reliably selected all randomised clinical trials comparing penfluridol to placebo or typical or atypical antipsychotic drugs for schizophrenia or serious mental illness.

DATA COLLECTION AND ANALYSIS

We independently extracted and analysed data on an intention-to-treat basis. We calculated the relative risk (RR) and 95% confidence intervals (CI) of homogeneous dichotomous data using a random effects model, and where possible calculated the number needed to treat. We calculated weighted mean differences (WMD) for continuous data.

MAIN RESULTS

We included twenty-five studies with a total of 1024 participants. Most of these studies were undertaken in the 1970s when penfluridol was launched. Ten studies, with 365 patients, compared penfluridol to placebo. In the meta-analysis of medium-term lasting studies, penfluridol was superior to placebo in the main efficacy measures: 'improvement in global state' (n=159, 4 RCTs, RR 0.69 CI 0.6 to 0.8, NNT 3 CI 2 to 10) and 'needing additional antipsychotic' (n=138, 5 RCTs, RR 0.43 CI 0.2 to 0.8, NNT 3 CI 1.8 to 20).A total of 449 patients from eleven studies were randomised to penfluridol or oral typical antipsychotics. There were no particular differences between penfluridol versus chlorpromazine, fluphenazine, trifluoperazine, thioridazine, or thiothixene for the main outcome measures in medium-term trials: 'improvement on global state' (N=2 studies), 'leaving the study early' (N=6), 'needing additional antipsychotic' (N=3), needing antiparkinsonian medication (N=2), and side-effects. Six studies, with 274 patients, compared penfluridol to depot typical antipsychotics. In general, for the efficacy and safety measures, no differences were established, but penfluridol was superior in keeping the patients in treatment; 'leaving the study early' (n=218, 5RCTs, RR 0.55 CI 0.3 to 0.97, NNT 6 CI 3.4 to 50).

AUTHORS' CONCLUSIONS

Although there are shortcomings and gaps in the data, there appears to be enough overall consistency for different outcomes. The efficacy and adverse effects profile of penfluridol are similar to other typical antipsychotics; both oral and depot. Furthermore, penfluridol is shown to be an adequate treatment option for people with schizophrenia, especially those who do not respond to oral medication on a daily basis and do not adapt well to depot drugs. One of the results favouring penfluridol was a lower drop out rate in medium term when compared to depot medications. It is also an option for chronic sufferers of schizophrenia with residual psychotic symptoms who nevertheless need continuous use of antipsychotic medication. An additional benefit of penfluridol is that it is a low-cost intervention.

Differential modulation of dopamine D2 receptors by chronic haloperidol, nitrendipine, and pimozide

Chronic administration of the neuroleptic haloperidol, the calcium channel antagonist nitrendipine, and the calcium channel antagonist neuroleptic pimozide produce differential effects on rat striatal 3H-spiperone binding. Following 7 days of 10 mg/kg i.p. administration, haloperidol significantly increases (p less than 0.01) dopamine D2 receptor binding to 123% +/- 6% of control values, whereas pimozide treatment significantly reduces (p less than 0.001) striatal 3H-spiperone binding to 46% +/- 6% of control values. Chronic administration of the calcium channel antagonist nitrendipine does not alter 3H-spiperone binding relative to control values. Saturation analysis reveals an increase in Bmax following chronic haloperidol and a decrease in Bmax following chronic pimozide treatment. No alterations in muscarinic cholinergic sites, dopamine uptake sites, or calcium channel antagonist sites result following chronic drug administration. These results are the first demonstration of a decrease in dopamine D2 binding sites after chronic neuroleptic treatment.

Antischizophrenic drugs of the diphenylbutylpiperidine type act as calcium channel antagonists

Antischizophrenic neuroleptic drugs of the diphenylbutylpiperidine class, which includes pimozide, fluspirilene, penfluridol, and clopimozide, inhibit [3H]nitrendipine binding with IC50 values of 13-30 nM. This inhibition involves receptors for the verapamil/prenylamine class of calcium channel antagonists. These diphenylbutylpiperidines also inhibit potassium-induced calcium-dependent contractions of rat vas deferens at concentrations of 40-350 nM. Other phenothiazine and butyrophenone neuroleptics lack such potent calcium-antagonist actions. Diphenylbutylpiperidines also differ from other neuroleptics in their ability to relieve negative symptoms of schizophrenia, such as emotional withdrawal, as well as the positive symptoms which respond to all neuroleptics. We suggest that these unique antischizophrenic actions are related to a blockade by diphenylbutylpiperidines of voltage-operated calcium channels.

Study of penfluridol and chlorpromazine in the treatment of chronic schizophrenia

This study presents data on the use of penfluridol, a once-a-week orally administered, antipsychotic agent, in the treatment of chronic schizophrenic patients. Fifty-nine patients participated in the initial dose titration segment during which doses of penfluridol were adjusted weekly until the patients' condition became stabilized. The starting dose did not exceed 60 mg per week, and the maximum weekly dose did not exceed 140 mg. Forty-one of these patients continued on to participate in a double-blind comparison of penfluridol with chlorpromazine. Maximum doses did not exceed 140 mg per dose per week for penfluridol and 7350 mg per week for chlorpromazine in the double-blind segment. Patients were abruptly switched from their previous neuroleptic medication to penfluridol without loss of control. Side effects, mainly extrapyramidal in nature, were readily alleviated with benztropine mesylate. Penfluridol, administered orally once a week, appeared to be well tolerated; it was comparable to daily chlorpromazine in treating and maintaining schizophrenic patients.