Isotretinoin vs Tretinoin: what is the difference?

How they differ

These two have the identical formula, C20H28O2, and identical weight, and they differ only in the geometry of one double bond. Tretinoin is all-trans retinoic acid, the natural active form of vitamin A, used topically for acne and photoaging and given systemically for one type of leukaemia. Isotretinoin is the 13-cis isomer, used by mouth for severe acne, where it shrinks sebaceous glands in a way topical retinoids do not. Both are potent teratogens, which is why isotretinoin is dispensed under strict pregnancy-prevention programmes in the US and Europe. That is the practical meaning of the pair: the same atoms, one bond flipped, and two very different regulatory regimes.

Side by side

Structural similarity 1.00 of 1, computed as a Morgan fingerprint Tanimoto coefficient. It measures shape, not effect.

Common questions

What is the difference between Isotretinoin and Tretinoin?

These two have the identical formula, C20H28O2, and identical weight, and they differ only in the geometry of one double bond. Tretinoin is all-trans retinoic acid, the natural active form of vitamin A, used topically for acne and photoaging and given systemically for one type of leukaemia. Isotretinoin is the 13-cis isomer, used by mouth for severe acne, where it shrinks sebaceous glands in a way topical retinoids do not.

Do Isotretinoin and Tretinoin have the same formula?

Yes. Both are C20H28O2 at 300.4 g/mol. They are isomers: the same atoms arranged differently, which is why they behave differently despite weighing the same.