Lipinski's rule of five

Meanings

1. A rule of thumb stating that a chemical compound is likely to be an orally active drug in humans unless it violates more than one of these criteria: (i) no more than 5 hydrogen bond donors (the total number of nitrogen–hydrogen and oxygen–hydrogen bonds); (ii) no more than 10 hydrogen bond acceptors (all nitrogen or oxygen atoms); (iii) a molecular mass less than 500 daltons; (iv) an octanol-water partition coefficient (log P) that does not exceed 5.

Etymology

The rule was formulated by Christopher A. Lipinski in 1997. Five refers to the multiples of five that occur in all of the criteria.