Posted by Cam W. on February 28, 2001, at 10:51:30
In reply to Re: Tardive Dystonia Question (Cam W?), posted by SLS on February 28, 2001, at 6:34:31
Scott - Risperdal probably causes more EPS than Clozaril and Zyprexa because when it was first marketed the doses recommended were in the 8mg to 12mg range. Subsequently, through clinical experience it was found that doses above 6mg/day greatly increased the incidence of EPS and that doses above 6mg/day are seldom more efficacious than those below this dosage (ie more is not necessarily better).
The reason that Risperdal causes more EPS than Zyprexa or Clozaril is that over 6mg/day Risperdal is saturating D2 receptors, making act more like a typical antipsychotic. When kept below 6mg/day (in most people) the incidence of EPS in comparable to low to mid-range doses of Zyprexa (7.5mg to 10mg/day).
Recent research has found that low doses of Risperdal (0.5mg - 1mg/day) are often enough for a therapeutic effect. Janssen really shot themselves in the foot when they came out with their original dosing guidelines. Risperdal is an effective drug when kept to lower doses, but the bad publicity in the past has really restricted it's use (unnecessarily).
Prolactin increases are also seen with Risperdal, but they are generally asymptomatic. I am not sure if they are dose related, but I do know that you do not see as many symptomatic cases (ie amenorrhea, galactorrhea, etc) at doses under 6mg/day.
Hope this helps - Cam
poster:Cam W.
thread:54845
URL: http://www.dr-bob.org/babble/20010221/msgs/55105.html