The haul has increased concerns about the thriving market for these types of drugs in Sunderland.
Thousands of steroids and Valium tablets – which can fetch up to £1 each – have now been taken off the streets thanks to the police operation.
Officers raided the property, in Hylton Road, Millfield, after concerned members of the community tipped off police.
Officers found the drugs and arrested a 27-year-old man on suspicion of possessing a controlled drug with intent to supply. He has been released on police bail pending inquiries.