OATP interactions

OATP1B1 and OATP1B3 are hepatic UPTAKE transporters: they carry drug from blood into the liver, so blocking them raises blood levels.

That direction is the thing to fix in mind. An efflux pump keeps drug out of the body; an uptake transporter pulls it into the organ that clears it. Inhibit OATP and the drug never reaches the hepatocyte, so it stays in the circulation and reaches the muscle instead.

The statins are the substrate group that matters — atorvastatin, simvastatin, rosuvastatin, pravastatin and pitavastatin — and myopathy is the endpoint. Cyclosporine, gemfibrozil and atazanavir are the inhibitors most likely to cause it; pibrentasvir and resmetirom also inhibit. Repaglinide, telmisartan and glecaprevir are the non-statin substrates shown.

Gemfibrozil and resmetirom appear on both sides of the page, inhibiting the transporter they are also carried by.

Do not confuse OATP with OAT. OATP is hepatic uptake and its story is statins and muscle; OAT is renal tubular secretion and its story is antibiotic clearance.