There's a few different things I do.
The largest pot you have full of boiling water down the drain is always helpful.
Liquid dishsoap followed by very hot water will take care of buildup from ointments/moisturizers. 1/4 cup of liquid dishsoap should do it.
Bleach, say two cups. Let it sit for at least 10 minutes then very hot water. This can be very irritating to the nose/eyes so I'm not too fond of it.
Equal parts baking soda followed by equal parts vinegar will make it foam and bubble for a bit. Again, let it sit for at least 10 minutes, then run very hot water down.
I am female, and was born in 1972 with Lamellar Ichthyosis.