Invega, the new atypical antipsychotic from Johnson & Johnson subsidiary Janssen-Cilag and follow-up to its blockbuster Risperdal is beginning to distinguish itself from both Risperdal, and from rival antipsychotics such as AstraZeneca’s Seroquel, according to research presented at psychiatry meetings on both sides of the Atlantic.

Schizophrenic patients treated using Invega (paliperidone) are much less likely to show weight gain than those treated with either Risperdal (risperidone) or Seroquel (quetiapine), says Dr Zafar Sharif, Columbia University College of Physicians and Surgeons, New York, USA. He believes that Invega’s extended-release delivery (via the osmotic delivery system developed by Alza Corp) smoothes peaks and troughs in plasma drug levels, leading to less histamine antagonism and therefore less weight gain.

According to data presented by Dr Sharif, only 8% of Invega-treated patients show a more than 7% increase in body weight, compared with 19% for risperidone and 23% for Seroquel. His colleague Dr Prakash Masand, Duke University Medical Centre, Durham, NC, USA, told a briefing held this week in Vienna, Austria (where both clinicians are attending the European College of Neuropsychopharmacology meeting) that weight gain is the leading reason for schizophrenic patients stopping antipsychotic medications.

In the USA, data from a placebo-controlled, double-blind study presented at the 20thAnnual US Psychiatric and Mental Health Congress, Orlando, Florida (Canuso C et al) showed significantly greater efficacy for Invega versus Seroquel (Positive and Negative Syndrome Scale, PANSS).

Dr David Walling of the Collaborative Neuroscience Network, UK, told the Vienna briefing that studies of Invega in other indications were now well advanced. Data from recently completed studies of Invega in bipolar disorder were currently ‘in house’ with J&J and should be available “within months”. Studies were also progressing of Invega in schizoaffective disorder “If these prove positive, it will be first time we will have a medication for schizoaffective disorder in the US – at the moment all treatment for schizoaffective disorder is off-label,” he said. By Ian Mason