Estudio de biodisponibilidad comparativa de dos formulaciones de risperidona existentes en el mercado chileno / 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. AIM: To compare the bioavailability of two risperidone formulations available in the Chilean market. MATERIAL AND 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 per cent confidence interval for the difference of long transformed mean pharmacokinetic parameters), the formulations Risperdal and Spiron, cannot be considered interchangeable.

[Amiodarone absorption and elimination after oral and intravenous administration in healthy individuals]. / Absorción y eliminación de amiodarona después de su administración oral e intravenosa en individuos sanos.

We studied amiodarone absorption and disposal in eight male healthy subjects aged 21 +/- 1 years old and weighting 69.8 +/- 7.1 kg. An intravenous dose of 5 mg/kg and an oral dose of 600 mg of amiodarone were administered. Amiodarone concentrations were measured by HPLC and calculations were performed using a compartment model independent pharmacokinetic analysis program. After oral administration a Cmax of 1.17 +/- 0.3 mg/ml was achieved at 3.25 +/- 0.46 h (tmax). Absolute bioavailability ranged from 50.4 to 87.8% (68.6 +/- 12.6%). Compared to previous reports, the variability of this parameter is similar and the mean value is one of the highest informed. After intravenous administration, Amiodarone had a half life of 7.53 +/- 0.96 h, a total body clearance of 4.25 +/- 0.73 ml/kg/min and a distribution volume of 2.99 +/- 0.71 l/kg. Except the later figure, which is in the inferior range, all other parameters are within previously reported values. It is concluded that amiodarone absorption and disposal values found in Chilean subjects are similar to those reported abroad.