[Mike Smith]

hello Mike Smith
one dose will not have any effect its a long process of continually staying with a routine  
you may not have any issues with mixing Finasteride with BO , best to try at least a research on side effect of Finasteride
 but this hold true for any thing you consider taking  ( including BO )

was Finasteride doctor prescribed?

Yes, the Finasteride was prescribed to me for an enlarged prostate.  Looks like the only thing I see on the interaction list that would apply is saw palmetto. The rest are other prescribed drugs, none of them hormones or such. One side effect of Finasteride that is only seen in about 1% of men is reduced amount of semen during sex. I do have that side effect.