Log P converter
Convert log P into the actual ratio it stands for, and into how much of a compound ends up in the oily layer.
That's 6.5× as greasy as aspirin, while an ideal oral drug is 3.2× greasier. About 99.01% of it ends up in the oily layer.
What it means
Where does it go?
Log P is for the neutral molecule. For anything that ionizes, log D at a stated pH is the figure that matters in the body.
Every unit
Your partition in every unit
Learn
Three things worth knowing
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The rule of five wants 0 to 5
Below zero a drug will not cross a membrane; above five it will not dissolve or leave. Most oral drugs sit between one and three.
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Why octanol
Octanol has an oily tail and a polar head, which makes it a passable stand-in for the lipid of a cell membrane. It was a practical choice in the 1960s and it stuck.
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High log P is not better
DDT has a log P near seven, which is why it stays in fat for decades. Greasy molecules get in easily and never leave.
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Background
About log P
Shake a compound with octanol and water and it divides between them. P is the ratio, and log P is its logarithm — so log P = 2 means a hundred times more in the oil.
It predicts almost everything about how a drug behaves: crossing membranes, binding to proteins, and being stored in fat rather than excreted.