Transporter Mediated Uptake of Montelukast

Leukotriene receptor antagonists (LTRAs) are frequently prescribed to reduce the symptoms associated with asthma. Singulair, manufactured by Merck, is a popular LTRA, however its effectiveness varies greatly between individuals. We are interested in understanding why the effectiveness of Singulair varies so greatly. For an oral drug such as Singulair to be effective, the body must efficiently absorb it. We have found that blood levels of Singulair vary greatly between individuals, and we think that this variability is responsible for variability in response. Drug absorption occurs primarily in the intestine. Due to differences in the chemical properties of drugs, some drugs can be absorbed easily while other drugs require help from special proteins produced by the cells that line the intestine. These proteins, or transporters act like turnstiles to allow drugs to move from the intestine to the bloodstream and are known to be inhibited by components of citrus juice. The activity of a transporter can be influenced by individual genetic variability. We think that Singulair requires help from a transport protein to be absorbed and that genetic variability in this transporter leads to variability in the blood level of Singulair. In this proposal we will use citrus juice (grapefruit and orange) to inhibit intestinal membrane transport proteins and show that Singulair requires these transporters to be efficiently absorbed. Eventually, what we learn from this work will allow doctors to quickly test individuals with asthma to determine how well they will absorb Singulair and possibly other LTRAs. Knowing this will allow the doctor to adjust the drug treatment on an individual basis to maximize benefit in the treatment of asthma.