Invega (paliperidone) is a new, once-a-day oral medication from Janssen for schizophrenia, also being studied for promotion as a bipolar treatment as well.  There are only three brief, 6-week studies which have been done, all funded by the manufacturer and all comparing Invega to placebo.  There is absolutely no evidence that Invega is superior to the many other less expensive traditional anti-psychotic alternatives available.  Invega is the 9-hydroxy metabolite of risperidone (Risperdal), which it responsible for most or all of risperidone's anti-psychotic effect.  Invega has similar side-effects to Risperdal, e.g. extra-pyramidal side-effects and prolactin elevation, except Invega may have no weight gain effect. 

Janssen advertising claims that Invega is a "powerful" anti-psychotic.  However, it is extremely unlikely that Invega is any better than any of the dozen other anti-psychotic medications available.

At least one study uses the increasingly popular and unreliable open trial initiation of treatment followed by a double-blind withdrawal phase in which half of the patients are switched to placebo (J Clin Psychopharm 2007 Feb;27(1):6-14).  This overrepresents the benefits of the medication, since initial treatment failures and side-effect drop-outs are eliminated and withdrawal effects may make the placebo group look worse than would have been the case.

Paroxetine (Paxil) and fluoxetine considerably increase the blood level of risperidone (J Clin Psychopharm 2005 Dec;25(6):527-32), but paliperidone is little affected.  Risperidone and paliperidone levels in mother's milk are one tenth that of blood levels for mothers on risperidone (J Psychopharm 2005 Mar;19(2):211-3) with infant blood levels 2%-5% of mother's (Ann Pharmaco 2004 Feb;38(2):273-6).

Invega is very expensive: 3 mg tabs for $380/month, 6 mg for $380, and 9 mg for $541 (Walgreen.com 3/11/07).  Some patients in the company studies were taking 15 mg/day which would cost $921/month or $11,000 per year.  In contrast, perphenazine would cost $920-$1840 per year at Walgreen prices for the top dose of 32 mg/day.  Haloperidol 10 mg/day would only cost $192 per year at Wal-Mart prices!  The Wal-Mart price for perphenazine would also be very low, since it, too, is covered by their generic program.