research
The effect of verapamil on in vitro susceptibility
of promastigote and amastigote stages of Leishmania tropica
to meglumine antimoniate
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Abstract
Pentavalent antimonials are the standard treatment
for cutaneous leishmaniasis (CL) with low efficacy and
resistance is emerging. CL is increased significantly in respect
to incidence rate and expanding to new foci. In the present
study, the effect of verapamil on in vitro susceptibility of
promastigote and amastigote stages of Leishmania tropica to
meglumine antimoniate (MA, Glucantime) was evaluated
using colorimetric assay (MTT) and in a macrophage model,
respectively. Verapamil, as a calcium channel blocker, affects
drug uptake by preventing of drug efflux from the cells. In
promastigote form, several concentrations of MA with or
without verapamil showed significant decrease (P<0.05) in
optical density. The overall mean IC50 value with combination of MA plus verapamil (IC50=116.03 μg/ml) was
significantly less than MA (IC50=225.14 μg/ml) alone
(P<0.05) for promastigote stage. Similarly, the amastigote
stage was more susceptible to treatment with MA plus
verapamil to that of MA alone (P<0.05). Analysis of overall
effect of different concentrations of MA alone, compared
with combination of MA plus verapamil by mean infection
rate of amastigotes in each macrophage showed a significant
difference (P<0.05).These findings indicated some degree of
synergistic effects between MA and verapamil on in vitro
susceptibility of L. tropica to MA. Further works are required
to evaluate this synergistic effect on animal model or
volunteer human subjects