Oh yeah, the structural similarity to modafinil is indeed astonishing.
Captodiamine is known to potentiate the action of barbiturates, thiobarbiturates, ketobemidone, pethidine, isomethadone, and morphine, most probably by inhibition of metabolising enzymes (CYP-family).
To my best knowledge, the exact molecular pharmacology (targeted receptor(s)) is not known, as captodiamine was abandoned some time ago and oviously nobody sees the need for new investigations.
Murphy