I have not seen any positive results of the use of Apistan in the fight against SHB, but some recommend using Coumaphos(Checkmite).
I would recommend a more enviromental friendly approach, as to avoid the possibilities of the developement of mite resistance to the chemicals mentioned above. Get a West Hive Beetle Trap, with the use of vegetable oil or FGMO, to suffocate the beetles in the trap.