Cystic echinococcosis (CE) is a widespread zoonosis caused by the species complex Echinococcus granulosus. Albendazole (ABZ)-the first-line anthelminthic drug for medical treatment of CE-is metabolized in vivo to the active derivative ABZ-sulphoxide (ABZ-SO). Target-site ABZ-SO concentrations in the hydatid cyst mediate the anthelminthic effect in CE. Primary outcome of this systematic review of individual patient data was the intra-cystic ABZ-SO concentration stratified by cyst size, location, calcification status and use of praziquantel. Studies reporting intra-cystic ABZ-SO concentrations in humans were identified by a systematic search. A pooled analysis of individual patient data was performed to assess intra-cystic concentrations. Pharmacokinetic data of 121 individual cysts were analysed. There was no correlation between plasma and intra-cystic ABZ-SO concentrations (rho = -0.03, p = 0.76). Intra-cystic drug concentrations were also not associated with sex and treatment duration. Use of praziquantel in combination with ABZ was associated with higher plasma (median 540 vs. 240 μg/L; p = 0.04) but not intra-cystic ABZ-SO concentrations (median 220 vs. 199 μg/L; p = 0.36). Relative drug concentrations in hepatic cysts were higher than in other cysts (0.8 vs. 0.4; p = 0.05). Intra-cystic concentrations were higher in calcified than non-calcified cysts (median 897 vs. 245 μg/L; p = 0.03). There was a trend towards higher intra-cystic concentrations in smaller sized cysts (β = -17.2 μg/L/cm; 95th CI, -35.9 to 1.6; p = 0.07). This study demonstrates that mean intra-cystic drug concentrations are similar to plasma concentrations on a population level. However, in individual patients plasma concentrations are not directly predictive for intra-cystic concentrations. The use of booster drugs was not associated with higher intra-cystic ABZ-SO concentrations in this analysis.
Keywords: Albendazole; Albendazole-sulphoxide; Cystic echinococcosis; Drug concentration; Echinococcus granulosus; Hydatid disease.