Do you have medicine for a cold?  你们有卖感冒药吗？

I'd like some pain-killers.  我想要一些止痛药。

Doctor, what is this for?  医生，这是治什么的？

How to take these medicine?  这些药怎么服用？

How many tablets do I take everyday?  我每天要吃多少片？

Does this drug have any side-effects?  这种药有什么副作用吗？

Can I drive after taking this medicine?  吃这个药后可以开车吗？

After taking this medicine, how long before I feel better? 
服用这个药多久之后我能有所好转？