A stable effervescent tablet, granule or powder composition free from excipients that may react with an effervescing organic acid component, comprising, an effective amount of a bisphosphonate bone resorption inhibitor, an effervescing organic acid component, an effervescing base component; wherein said composition is free of polyol binders and tableting lubricants; has a loss on drying of 0.25% (m/m) or less; has a complete disintegration time of no more than 180 seconds when placed in 3 to 8 fluid ounces of water at between 5-20° C.; and said bisphosphonate is incorporated as a micronized particle or by spray drying and is completely solubdised in water within 2 minutes without stirring.