Extra Buttons on DeathAdder Not Working

I am using a Razer DeathAdder left handed edition on a Mac running OS X Mavericks. When I try to map the controls to the side buttons, they register as button 3 instead of 4 and 5. Therefore, the extra buttons (one of the main reasons I purchased this mouse) are unusable - they act as pick block, which is what I have button 3 set to