Little efficacy difference between old and new antipsychotics

By Eleanor McDermid, Senior medwireNews Reporter

Older and second-generation long-acting antipsychotics have broadly similar clinical efficacy, shows a randomised trial in JAMA.

However, the researchers say the results of the trial, which compared paliperidone palmitate with haloperidol decanoate in 311 patients with schizophrenia or schizoaffective disorder who were at risk of medication nonadherence, “do not rule out the possibility of a clinically meaningful difference” between the medications.

During up to 24 months of follow-up, the efficacy failure rates were 33.8% with paliperidone palmitate and 32.4% with haloperidol decanoate, giving a hazard ratio of 0.98. But the 95% confidence interval was 0.65 to 1.47, which does not rule out either drug being better than the other.

The patients received monthly injections at average doses ranging from 129 to 169 mg for paliperidone palmitate and from 67 to 83 mg for haloperidol decanoate.

In an accompanying editorial, Donald Goff (New York University School of Medicine, USA) says: “It is increasingly clear that results from early industry-sponsored studies that favored the newer agents may have been biased by excessively high dosing of the older comparator drug.”

He also highlights the differing efficacy and adverse effect profiles between second-generation drugs, which makes “broad comparisons between first- and second-generation agents potentially misleading.”

The two medications in the current study had different adverse effect profiles; notably, patients taking paliperidone palmitate gained weight, whereas those taking haloperidol decanoate lost weight. There were no differences in lipid and glycaemic profiles and, contrary to the researchers’ expectations, there was no significant increase in rates of abnormal involuntary movements, probable tardive dyskinesia or parkinsonism in patients taking haloperidol decanoate versus paliperidone palmitate.

However, global scores on the Barnes Akathisia Scale increased significantly more among patients taking haloperidol decanoate versus paliperidone palmitate, at 0.73 versus 0.45, and more of the former group started taking medications to control akathisia (11.0 vs 3.6%) or parkinsonism (29.3 vs 15.8%).

This thereby partly confirms “that paliperidone palmitate has a lower propensity to cause extrapyramidal symptoms than haloperidol decanoate”, say study author T Scott Stroup (College of Physicians and Surgeons, Columbia University, New York, USA) and colleagues.

In his editorial, Goff says that, aside from the large cost differences between older and second-generation antipsychotics, the findings “suggest that drug selection should be based on anticipated adverse effects rather than efficacy.”

But he notes that more research is needed to guide drug selection, and adds: “Not only is the compilation of reliable data about these drugs essential, so also is the clear communication of this information to patients as part of the shared decision-making process.”

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