Abstract:
Background: Praziquantel (PZQ) is an antihelminthic drug whose P-glycoprotein (P-gp) substrate specificity has not
been conclusively characterized. We investigated its specificity by comparing its in vitro intracellular accumulation
in CEM (parental), and CEM VBL cells which over express P-gp, a drug efflux transporter. Saquinavir (SQV), a known
substrate of efflux transporters was used as control.
Methods: A reversed phase liquid chromatography method was developed to simultaneously quantify PZQ and
SQV in cell culture media involving involved a liquid - liquid extraction followed by ultra-high performance
liquid chromatography using a Hypurity C 18 column and ultraviolet detection set at a wavelength of 215 nm.
The mobile phase consisted of ammonium formate, acetonitrile and methanol (57:38:5 v/v). Separation was
facilitated via isocratic elution at a flow rate of 1.5 ml/min, with clozapine (CLZ) as internal standard. This
was validated over the concentration range of 1.6 to 25.6 μM for all analytes. Intracellular accumulation of
SQV in CEM VBL was significantly lower compared to that in CEM cells (0.1 ± 0.031 versus 0.52 ± 0.046, p = 0.03
[p <0.05]).
Results: Accumulation of PZQ in both cell lines cells were similar (0.05 ± 0.005 versus 0.04 ± 0.009, p = 0.4)
suggesting that it is not a substrate of P-gp in CEM cells. In presence tariquidar, a known inhibitor of P-gp,
the intracellular accumulation of SQV in CEM VBL cells increased (0.52 ± 0.068 versus 0.61 ± 0.102, p = 0.34 in
CEM cells and 0.09 ± 0.015 versus 0.56 ± 0.089, p = 0.029 [p < 0.05] in CEM VBL cells). PZQ did not significantly
affect the accumulation of SQV in either CEM (0.52 ± 0.068 versus 0.54 ± 0.061, p = 0.77), or in CEM VBL cells
(0.09 ± 0.015 versus 0.1 ± 0.031, p = 0.89) cells compared to tariquidar, implying that PZQ is not an inhibitor of
P-gp in CEM VBL cells.
Conclusions: PZQ is neither a substrate nor an inhibitor of the efflux drug transporter P-gp in T-lymphoblastoid cells,
CEM and CEM VBL . We also report a simple, accurate and precise method for simultaneous quantification of
PZQ and SQV.
