The effects of
ivermectin at a concentration of 3.13 x 10(-6) M used in combination with other
antiparasitic drugs on the viability of adult Onchocerca in vitro were assessed using MTT colorimetry and worm motility levels. When
ivermectin was used against male O. gutturosa over
a 7 d period in combination with
suramin (5 x 10(-5) M),
CGP 6140 (3.13 x 10(-6) M),
CGP 20376 (1.95 x 10(-7) M),
mefloquine (3.13 x 10(-6) M),
levamisole (3.13 x 10(-6) M),
mebendazole (5 x 10(-5) M),
flubendazole (5 x 10(-5) M) and
albendazole (5 x 10(-5) M), there was either no increased effect or only a marginally increased effect on motility levels when compared with the use of
ivermectin alone. MTT colorimetry revealed that in most cases there was a cumulative effect of the 2 drugs used in combination but not a synergistic effect. In a trial extended to 26 d it was demonstrated that the combination of
ivermectin and
suramin did not produce a greater inhibition of motility than
ivermectin alone. Using female O.
volvulus, the activity of
ivermectin,
CGP 6140 and the 2 drugs combined was examined. The motility of all 3 groups exposed to
drug(s) was suppressed by 24 h compared with controls. MTT colorimetry performed on day 7, using the pre-weighed anterior end of each worm, illustrated that
ivermectin alone produced a 43.4% inhibition of
formazan formation compared with controls,
CGP 6140 alone produced 50.6% inhibition, while the
drug combination produced a 72% inhibition, equivalent to the heat-killed control.(ABSTRACT TRUNCATED AT 250 WORDS)