INVESTIGADORES
ALVAREZ Luis Ignacio
congresos y reuniones científicas
Título:
Development of a cyclodextrin-based flubendazole formulation to control secondary echinococcosis: pharmacokinetics, hydatid cyst morphology and efficacy in mice.
Autor/es:
CEBALLOS, L.; ALVAREZ, L.; SANCHEZ BRUNI, S.; ELISSONDO, C.; DENEGRI, G.; LANUSSE, C.
Lugar:
Torino, Italia
Reunión:
Congreso; 10th International Congress of the European Association for Veterinary Pharmacology and Toxicology; 2006
Institución organizadora:
European Association for Veterinary Pharmacology and Toxicology
Resumen:
  Introduction: Cystic echinococcosis (CE) caused by the metacestode (larval) stage of Echinococcus granulosus is an important public health problem worldwide. Surgery and chemotherapy are the most used strategies to treat CE in man. Albendazole and mebendazole are currently used for CE treatment with highly variable clinical success. A flubendazole (FLBZ) suspension has also been assayed against CE in vivo, showing poor efficacy (1). However, FLBZ demonstrated a marked in vitro effect against E. granulosus protoscoleces (2). FLBZ is poorly soluble in water which accounts for limited gastrointestinal (GI) dissolution, low absorption/systemic availability and poor clinical efficacy after its oral administration. Thus, the use of pharmacotechnical strategies to overcome these limitations may improve the in vivo efficacy of FLBZ against CE. Cyclodextrins (CDs) are used in pharmaceutical formulations to enhance solubility of poorly water soluble drugs. The goals of the current work were: a) to compare the plasma pharmacokinetic (PK) behaviour of FLBZ formulated as either an aqueous CDs-solution or aqueous suspension, both given by the oral route to mice,  b) to compare FLBZ efficacy against secondary CE in mice after its administration as both formulations, c) to compare the chemoprophylactic effect observed for both FLBZ formulations, and d) to evaluate FLBZ-induced morphological changes in hydatid cysts recovered from infected mice treated with both drug formulations. Materials and Methods:  a) PK study: Balb/c mice were allocated into two groups.  Group 1 (n= 44): animals were orally treated with a CDs-based aqueous solution of FLBZ (FLBZ 0.5 mg/ml, CDs 10%) at 5 mg/kg. Group 2 (n= 44): mice were orally treated with an aqueous suspension of FLBZ in carboximethylcellulose (CMC) (FLBZ 0.5 mg/ml, CMC 0.5 %) at the same dose rate. Blood samples were collected at different times during 16 h post treatment, and plasma analyzed for FLBZ/metabolites by HPLC. The estimated PK parameters were statistically compared by using a non-parametric test. b) Efficacy study: Thirty (30) Balb/c mice were infected by i.p. inoculation of 1500 protoscoleces/animal. Three months after infection animals were divided into three groups: I- Control (animals received saline solution orally as a placebo), II-FLBZ-CDs (animals were orally treated with the same FLBZ-CDs solution used in the PK study) and III- FLBZ-CMC (animals were orally treated with the same FLBZ-CMC suspension used in the PK study). All FLBZ treatments (5 mg/kg) were performed twice a day during 25 days. After treatment, all animals were killed and necropsied to collect the hydatid cysts. The weight of the cysts collected from each animal was recorded. The same experimental protocol was followed in 6-month and 9-month infected mice. Cyst weight differences between groups were analysed by ANOVA plus Tuckey test. c) Chemoprophylactic study: Thirty (30) Balb/c mice were infected by i.p. inoculation of 1500 protoscoleces/animal.  One day after infection the animals were allocated into three groups to receive the treatments above described. The chemoprophylatic FLBZ treatments were given twice a day during 15 days. At six months post-infection, the animals were killed to collect parasite cysts. Cyst weight differences among treatment groups were analysed by ANOVA plus Tuckey test. d) Morphological study: Cyst samples recovered from infected-treated mice from the Efficacy study were prepared for scanning (SEM) and transmission (TEM) electron microscopy to evaluate FLBZ-induced morphological alterations.  Results: FLBZ administration as a CDs-based solution resulted in a significantly higher (>450%) plasma Cmax compared to that obtained after the FLBZ-CMC treatment. This enhanced availability was well correlated with the increased efficacy observed for the FLBZ-CDs formulation in animals treated at 3 and 9 months post-infection, where the suspension (FLBZ-CMC) formulation did not reach differences in efficacy with the control group (Efficacy Study). However, no statistical differences in cyst weight between both formulations were observed in the Chemoprophylactic Study. Both assayed formulations showed similar FLBZ-induced ultrastructural morphological changes after the TEM and SEM studies, including alterations in the germinal layer with the presence of numerous vacuoles and lipid droplets.   Discussion and Conclusion: CDs increased FLBZ water solubility, which accounted for enhanced absorption and bioavailability in mice. This improved PK behaviour permitted higher drug exposure of the hydatid cysts which enhanced FLBZ clinical efficacy in echinococcosis. Lower FLBZ concentrations were required to achieve good efficacy against protoscoleces in the early stage of infection (chemoprophylaxis). In conclusion, FLBZ may be a suitable drug for treating CE and the use of pharmacotechnically-based strategies would be helpful to improve clinical efficacy of benzimidazole anthelmintics to treat the hydatid disease.   References 1. Davis et al. Bull World Health Org 1986; 64: 333-388. 2. Elissondo et al. Parasitol Res 2005; 22: 1-7. Acknowledgments. The authors acknowledge Dr. Kathleen Vlaminck (Janssen Animal Health, Beerse, Belgium) and Dr. Gustavo Viana (Janssen, Buenos Aires, Argentina) for providing FLBZ and metabolites used in the present experimental work.