It's time to give your medicine cabinet an emetic. Purge it now of all expired medications, beauty products you know you'll never use and any other useless crap clogging up your shelves.
Prescription drugs, especially antibiotics, hormone medications, and antidepressants should never be flushed down the toilet. Modern treatment facilities are not designed to remove those medications. You can minimize their impact on the environment by taking all your unwanted or expired medicines to an appropriate disposal facility. Find out where by calling your local pharmacist; in many of the saner parts of the world, this safe facility will be your pharmacist. You may also be able to find information on the web through a site like Safe Drug Disposal California (which I have quoted above).
Unused and non-rancid cosmetics and other sundries can often be donated to local homeless shelters. Into the Charity bag!
If you think you might need something, but you haven't needed it in the last year, put it in a box or a bag with a label saying "Dispose of this after [a date 6 months from now]".
For bonus points: now that there's less clutter, take a moment to wipe down all the shelves. Mmm, happy bathroom.