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SLCO1B1 and medicines


When you take a medicine (drug), your body has to have a way to handle the medicine. One way is for carriers to transport medicines. A transporter called solute carrier organic anion transporter family member 1B1 (SLCO1B1) helps the body get rid of certain medicines after they are no longer needed.

Pharmacogenetic testing

DNA is like a set of instructions for your body that can help determine how your body will work. Each person differs from another at the DNA (gene) level. This means that each person has small differences in the genes that code for transporters. The part of DNA that instructs how well the SLCO1B1 transporter will work is called the SLCO1B1 gene. The study of how genes like SLCO1B1 affect the way your body handles medicines is called pharmacogenetics (FAR mah coh je NEH tiks).

Differences in your DNA that make up the SLCO1B1 gene can change how well you are able to handle certain medicines. By testing your DNA (with a pharmacogenetic test), we may find differences that can allow us to predict how well the SLCO1B1 transporter will work. The results of this test will guide your doctor to choose the correct dose of medicine to give you if you need to take a medicine that is affected by SLCO1B1. The results of your SLCO1B1 pharmacogenetic test will place you into one of three groups:

  • Normal (high) function – This means there are two copies of the normal activity SLCO1B1 gene. This results in normal SLCO1B1 function. About 7 out of every 10 people have normal (high) function. There is no reason to use genetic test results to adjust the normal dose of medicines that are affected by SLCO1B1 if you are in this group.
  • Low function – People in this group are at a very high risk for having side effects from medicines that are affected by SLCO1B1. Patients who have low SLCO1B1 function might need a different dose of medicine or even a different medicine that is not affected by SLCO1B1. About 1 out of every 20 people have low SLCO1B1 function.
  • Intermediate (medium) function – People in this group have medium SLCO1B1 function. It falls between that of the low and high SLCO1B1 function patients. People who have medium SLCO1B1 function may require lower doses of certain medicines that are affected by SLCO1B1 to avoid side effects. About 2 out of every 10 people have medium SLCO1B1 function.

Medicines that may be affected

The SLCO1B1 transporter aids in the breakdown of many medicines, including simvastatin – a medicine used to lower cholesterol levels.

The result of your SLCO1B1 test will place you into one of the three groups above. Knowing what group you are in may help your doctor pick the right medicine and right dose for you. For example, with simvastatin this might be the outcome:

  • Patients with low SLCO1B1 function may have more side effects (like muscle pain) from simvastatin and may require a different agent to lower cholesterol.
  • Patients with intermediate SLCO1B1 function may have more side effects (like muscle pain) from a normal dose of simvastatin and may need a lower dose.
  • Patients with normal SLCO1B1 function don’t need dose changes when taking simvastatin.

Scientists continue to find new information about which medicines are affected by gene test results. For details about which medicines are affected by SLCO1B1, please go to or


If you have questions or concerns about pharmacogenetic testing at St. Jude, call one of the Pharmaceutical Sciences research nurses at 901-595-2482 or email If you are calling from outside of the Memphis area, dial toll free 1-866-2ST-JUDE (1-866-278-5833), then dial extension 2482.


This document is not intended to take the place of the care and attention of your personal physician or other professional medical services. Our aim is to promote active participation in your care and treatment by providing information and education. Questions about individual health concerns or specific treatment options should be discussed with your physician.

St. Jude complies with health care-related federal civil rights laws and does not discriminate on the basis of race, color, national origin, age, disability, or sex.

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