PURPOSE: To obtain a medicine tending to concentrate to the bone tissue, having both bone resorption-suppressive activity and osteogenesis-promotive activity, thus useful as an osteopathy therapeutic agent, containing a compound formed by covalent bonding between a specific antibiotic and a steroid through a linker.

CONSTITUTION: This medicine contains a compound of formula I X-Y-Z {X is a monovalent group of formula II (R1 and R2 each is H or OH; R3 is H or CH3; R4 is H, a halogen, etc.); Y is a divalent group of formula III (X is a direct bond, O or NH; (n) is 0-4), formula IV (X is the same as the X in formula III), etc.; Z is a monovalent group freed from the H and OH at 2-, 3-, 4-, 6-, 7-sites, etc., of a compound of formula V [R1' is CH3 or C2H5; R5' is OH, acetyl, etc.; R6' is H, OH, etc.; R7' is H, OH, etc.]}, e.g. 1,3-N-4-[17-oxy- estra-1,3,5(10)-triene-3-oxyethyl]-piperazine-1-methylene-tetracycline.