Don't prescribe drugs based on race but on genotype.
Prescribing on the basis of a patient's presumed race or ethnicity is for the birds. More important than skin color or presumed ethnicity is the person's genotype, speakers said at a special session on "Racial/Ethnic Differences in Drug Response and Pharmacokinetics." The session was part of the annual meeting of the American Society for Clinical Pharmacology & Therapeutics (ASCPT), held recently in Washington, D.C.
Julie Johnson, Pharm.D., professor and chair of the department of pharmacy practice at the University of Florida, Gainesville, led off the discussion, finding fault with both ethnicity and race in terms of prescribing. The prescribed U.S. Office of Management and Budget guidelines call for only a Hispanic/non-Hispanic breakdown. "That leaves a lot of ethnicities out there," she said, adding that "prescribing by ethnicity has a very low level of predictability."
Her review of the literature, Johnson said, "indicates no differences in any of the pharmacokinetic processes that are passive or involve passive absorption. Where there are differences by race or ethnicity are in gut metabolism and gut transport, the hepatic first-pass effect, renal tubular secretion, or binding of alfa-fetaprotein compared with albumin." Most of the literature on such active processes, she noted, centers on hepatic metabolism.
But even using these categories to prescribe by race can lead one astray, she said. "There are examples in the literature of blacks having higher metabolism compared with whitesand for having lower metabolism."
A number of papers indicate racial differences in pharmacokinetics for some drugs, she told the audience. "But they don't translate into any important differences in drug response because of their wide therapeutic index" except possibly in the category of cardiovascular drugs.
The oldest and best-recognized racial differences, she continued, were those between blacks and whites in their response to beta-blockers versus diuretics for control of hypertension. (Blacks respond better to diuretics, whites to beta-blockers.) But she added that, even in this well-known example, one could be misled.
In a recent study she did, Johnson found that in the response of blacks and whites to beta-blockers, what counted was haplotype (a combination of genotypes on the same chromosome). The haplotype most responsive to beta-blockers was carried by 42% of Caucasians but only by 18% of African-Americans. "We believe genotype is a much better way to describe a person's drug response than race. Our evidence shows that if a black person has the right genotype, he will respond very well to the drug."
Panelist Nicholas Schork, Ph.D., of the University of California, San Diego, agreed that race is no way to predict drug response. In the United States, where there is a considerable admixture of races, there are many genetic variants in individuals classified as of a certain race, he explained. For example, about 20%-25% of the genome in African-Americans is of European ancestry.
Pilar Ossorio, Ph.D., J.D., of the University of Wisconsin schools of law and medicine, agreed that using race as a basis for prescribing poses difficulties. Race-conscious research and medical care can harm people of color, by "reinforcing negative stereotypes." Physicians may withhold effective drugs, she said, when they mistakenly apply statistical information about a group to an individual.
Betsy Sleath, Ph.D., R.Ph., of the University of North Carolina, Chapel Hill, school of pharmacy, underscored the inadequacy of predicting drug response by racial/ethnic categories as the U.S. population becomes more racially and ethnically diverse. It is more important, she said, to understand different health beliefs and cultures (including medication-taking behavior). Members of minority groups may also be less able to understand how to take their medications, feeling doctors don't listen to them. This is more of a problem as many physicians spend less time with individual patients.
As to language, Sleath said her state is "exploding with Hispanics." A survey of pharmacists in 1998 showed that 83% were serving Hispanics. Only 4% were fluent in Spanish, yet 42% said they needed Spanish in their practice. "Our university is trying to address this problem and develop Web-based courses" and "our board of pharmacy has created a campaign with wall posters in Spanish, so a patient can point to them and get a prescription label in their own language.
"Still, this may not be enough for a patient taking a complicated medication," Sleath said. One particular problem is the use of the word once on a prescription label. Once in Spanish means not "one time," but the number "11."
Jean McCann. Color of skin no way to prescribe drugs.
May 19, 2003;147:23.