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CYP - Cytochrome P450

OATP - Organic anion transporting polypeptide

Organic anion transporting polypeptide (OATP), sometimes referred to by its gene name SLCO1A2, SLCO1B1, SLCO1B3, etc., is a family of transport molecules located in cell membranes that transport negatively-charged drugs (anions) from the blood into cells (influx) to be metabolized. Currently, eleven different OATPs have been discovered. OATP1B1 and OATP1B3 are the most studied, while OATP2B1 and OATP1A2 have limited data. The remaining polypeptides are not well characterized.
OATP should not be confused with with OAT1, OAT2, OAT3, etc., which are another family of transporters

Inducers - OATP inducers increase transporter activity, decreasing exposure to substrates
Inhibitors - OATP inhibitors block transporter activity, increasing exposure to substrates
One drug may inhibit or induce multiple transporters and enzymes (e.g. p-glycoprotein, OATP, CYP3A4)
Some OATP substrates also simultaneously inhibit the transporter
Inducers and inhibitors can be subdivided into strong, moderate, or weak, depending on the degree of their effect

If two drugs are transported by the same OATP, they may "compete" for the transporter, altering the metabolism of one or both of the drugs

Information on drug interactions can be difficult to assimilate
Certain drug interactions and metabolic pathways are well-defined while many are not

During drug development, the FDA requires interaction testing with medications that are known to have significant effects on CYP enzymes and transporters. Obviously, there is no way to test a new drug with every medication available, meaning most drugs come to market with incomplete interaction profiles. After the medication is prescribed to a large number of people, other drug interactions are inevitably discovered.

Drug research often occurs in a laboratory setting (in vitro) with animals and cell cultures. Findings from these experiments do not always reflect what happens in the human body (in vivo).

Drug metabolism is an evolving field, and researchers are just beginning to understand all the different ways the body eliminates medications. Cytochrome P450 enzymes have been studied for a while, but cell transport systems (e.g. p-glycoprotein, OAT) are a relatively new area of pharmacology, and their role in drug elimination has not been completely elucidated.

Not all drug interactions are known or can be predicted
Good information on possible drug interactions may not be available
Not all drug interactions are clinically significant, and patients should consult their healthcare provider if they are concerned about a possible interaction
Drug interaction checkers provide the most efficient and practical way to check for interactions among multiple medications. A free interaction checker is available from Drugs.com (see Drugs.com interactions checker).

ORGANIC ANION TRANSPORTING POLYPEPTIDE (OATP)