Tretinoin

Tretinoin is a pharmaceutical. As a creme, it is used to treat acne. However, as an oral medication, it is used to treat acute promyelocytic leukemia.
The side effects depend on how the medication is administered. When administered to skin, it can cause redness, skin peeling and sensitivity to the sun. As an oral medication, it's side effects are more severe and include shortness of breath, headache, depression, hair loss, vomiting, muscle pain and vision changes. More severe side effects include increase in white blood cell count and clotting. Skin cremes containing tretinoin should not be used by pregnant women. 
Tretinoin at Wikipedia
Category:Pharmaceuticals