For men and women, differences in how drugs react

<p>Gender equality has its place, but when it comes to the effects of many medications, men and women are not equal.</p><p>In general, women have lower body weights, slower gastrointestinal motility, less intestinal enzyme activity, and slower kidney function than men. All of these differences affect the way drugs act in the body. And because much of the research has been done on men, it comes as no surprise that women are 50 to 75 percent more likely than men to experience an adverse drug reaction.</p><p>Differences in body composition between men and women lead to differences in body distributions of medications. Women, even those who are not obese, have larger fat stores than men. </p><p>Some medications are naturally stored in fat, so women who take these drugs are more sensitive to drug effects and will notice a longer duration of action.</p><p>This is especially significant in common anti-anxiety medications like Xanax, Valium, and Ativan. In general, women need smaller doses of drugs that bind to fat. </p><p>Men have increased stomach acid, so drugs that require an acidic environment work better in men than in women.</p><p>Women can compensate by taking these drugs with orange juice or another equally acidic drink.</p><p>Antibiotics taken for fungal infections, like ketoconazole, are an example of drugs affected by stomach acidity. </p><p>Men also have faster moving gastrointestinal tracts than women. To compensate, women need to wait longer after eating a meal before taking drugs that must be taken on an empty stomach.</p><p>Ampicillin, captropril, levothyroxine, and Claritin are all drugs affected by this physiologic variation.</p><p>Men have faster metabolisms, so they clear many drugs much faster than women do. Tylenol, caffeine, and digoxin are a few of the medicines that move more quickly through the male body. Women who take the blood thinner known as Coumadin usually need less of it than men, simply because they metabolize it more slowly. </p><p>Kidneys filter 10 to 25 percent more slowly in women than in men. Many antibiotics, digoxin, Neurontin and Lyrica all require smaller dosages in women because they are cleared from the body much less rapidly by a woman's kidneys. </p><p>But not all medication disparities are due to the differences in body types between men and women. It appears that some differences are not directly related to body composition or a particular physiologic process.</p><p>Women treated with digoxin for heart failure require smaller doses than men. We still don't know the complete physiologic explanation, but we do know that if given a man's dose of digoxin, women have a significantly higher risk of death.</p><p>Beta blockers (metoprolol, for example) lower blood pressure and decrease heart rate.</p><p>But in women, especially while exercising, beta blockers work much more effectively than in men. This means that a woman taking regular beta blockers may have an uncomfortable drop in blood pressure during her morning workout. If she is not aware of this possible side effect, she may be surprised by feeling light-headed and weak when she exercises. </p><p>Women who are clinically depressed appear to respond well to SSRIs like sertraline (Zoloft) while men with depression respond better to a class of drugs called tricyclic antidepressants, like amitriptyline (Elavil). Choosing which anti-depressant to treat serious clinical depression can be guided by these known gender differences.</p><p>Estrogen influences pain pathways, making women more susceptible to pain but also more responsive to morphine. </p><p>Men require a 30 percent to 40 percent larger dose of morphine than women do. It's not that they are less tolerant of pain; it's that their bodies process opioids differently than women. Women are also more likely to experience common side effects of opioids like sedation and difficulty breathing.</p><p>It's easy to see how different women and men are — even when it comes to medications and dosages. It may be wise to ask your doctor about your medication choices and dosages, and to check with your pharmacist about dosing based on your gender.</p><p>After all, the right drug at the right amount may depend on whether you are a man or a woman.</p><p>Dr. Stacey Kerr, a longtime Sonoma County family physician, graduated from UC Davis Medical School and has been certified in her specialty by the American Board of Family Medicine. Her columns are not intended as a substitute for hand-on medical advice or treatment. Consult your health care provider before adhering to any recommendations in this column. Email comments to drkerr@the-doctors-inn.com.</p>