[Comparative bioavailability study of two formulations of risperidone available in the Chilean market].
BACKGROUND
Bioavailability of a particular drug can vary according to the formulation used. Therefore, studies of comparative bioavailability of different formulations of a same drug are worthwhile.


OBJECTIVE
To compare the bioavailability of two risperidone formulations available in the Chilean market.


METHODS
The bioavailability of a local risperidone formulation (Spiron) was compared with the original formulation of the drug (Risperdal) in 12 healthy volunteers, aged 19 +/- 1 years. A single dose of 3 mg was given orally, using a randomized double blind protocol in two periods. Fifteen blood samples were obtained at regular intervals, until 24 h after drug administration. Risperidone plasma levels were measured by high pressure liquid chromatography. pharmacokinetic parameters were calculated using a computer program that is independent of compartmental analysis.


RESULTS
The area under the curve of plasma concentration versus time, from 0 to infinite (ABC0-infinity) and from 0 to 24 h (ABC0-24), early exposure (ABC from 0 to maximal time) and maximal plasma concentrations were significantly lower for Spiron. Half life time and time to achieve the maximal concentration were similar for the two formulations.


CONCLUSIONS
According to bioequivalence tests suggested by the Food and Drug Administration (FDA) of the United States (90% confidence interval for the difference of long transformed mean pharmacokinetic parameters), the formulations Risperdal and Spiron, cannot be considered interchangeable.
Gaete
Leonardo E
LE
Programa de Farmacología Molecular y Clínica, ICBM, Hospital Clínico de la Universidad de Chile. lgaete@machi.med.uchile.cl
Solís
Jaime
J
Venegas
Pablo
P
Carrillo
Mitzy J
MJ
Schatloff
Oscar
O
Saavedra
Iván
I
D000293:Adolescent; D000328:Adult; D014150:Antipsychotic Agents / Q000009:adverse effects / Q000493:pharmacokinetics*; D001682:Biological Availability; D002677:Chile; D004311:Double-Blind Method; D006801:Humans; D008297:Male; D018967:Risperidone / Q000009:adverse effects / Q000493:pharmacokinetics*; D013810:Therapeutic Equivalency
D014150:Antipsychotic Agents; D018967:Risperidone