If you are a man and take a sleeping pill in the middle of the night, you may fall asleep quickly and wake up feeling refreshed. If you’re a woman and take the same pill, you may fall asleep just as fast but find that you are slogging through the morning with a drug-powered hangover.
Just a fluke? Absolutely not.
An under-recognized problem: While scientists have long suspected that men and women don’t respond in the same ways to certain drugs, a growing body of research shows that these differences are more significant than previously thought.
Why this matters: You may be taking a drug—or be prescribed one in the future—in a dose that’s not right for you…or in a class that is not the most effective for your condition. What you need to know…
Since 1992, when the sedative zolpidem (Ambien) was first introduced in the US, the recommended maximum dose for men and women has been the same—10 mg.
A startling finding: Recently, evidence came to light that women who took the same dose of zolpidem as men had blood levels that were 45% higher. The “standard” dose, in other words, was essentially an overdose for women.
Meanwhile, zolpidem has also been implicated in cases of so-called “sleep driving,” in which people
who have taken the drug drive their cars while not fully awake.
Now the FDA has stepped in and cut the recommended dose of zolpidem for women in half, to 5 mg. The daily dose for the extended-release version is up to 12.5 mg for men and 6.25 mg for women.
But it’s not just sleeping pills that affect men and women differently. Entire classes of medications—such as beta-blockers, opioid painkillers and heart medications—have sex-specific effects.
Why haven’t we heard more about this?
Until the early 1990s, women of childbearing age were excluded from most drug-based research. The majority of drugs were tested only in men. Based on these results, doctors assumed that any research that cleared a medication as being safe and effective for men would also apply to women—but they didn’t really know.
Today, medications are routinely tested in roughly equal numbers of men and women—but there are still hundreds, maybe thousands, of drugs on the market whose outcomes have never been analyzed based on gender. What’s more, data do not always separate outcomes based on age, ethnicity and other factors. So the recommended dose may not be the optimal amount for certain people.
You’d expect that a small woman would require a lower dose of medication than a large man. But size is only one difference.
Because women have a higher percentage of body fat, on average, drugs that are lipophilic—that is, accumulate in fatty tissue-cause longer-lasting effects in women than in men. On top of that, women tend to metabolize (break down) some medications more slowly than men, so women can be more likely to accumulate higher-than-expected concentrations of those drugs in their bodies.
A woman’s digestive process is also generally slower than a man’s, which means that women may have to wait for a longer time after meals in order to take some medications “on an empty stomach.”
Trust your gut: If you start taking a new medication and your instincts tell you that something’s wrong, pay attention. You may need a different drug or dose.
The research on sex-based drug effects is still in the early stages. There are probably hundreds, if not thousands, of drugs that affect men and women differently.
Among the drugs that women should use with caution…
SEDATIVES
Benzodiazepine sedatives, such as diazepam (Valium), accumulate in fat and have longer-lasting effects in women. Women may find themselves feeling drowsy the next day…less alert than usual…and having slower reaction times. (Zolpidem, the medication discussed earlier, has similar effects.)
My advice: If you are a woman taking one of these medications for anxiety, back spasms or any other condition, ask your physician, “Could I take a lower dose because I’m a woman?”
Beta-blockers, such as metoprolol (Lopressor), atenolol (Tenormin) and propranolol (Inderal), have stronger effects on women. For example, women who take them tend to have a greater drop in blood pressure and heart rate than men, particularly during exercise.
My advice: All patients should be started on the lowest possible dose, then gradually adjusted (titrated) every few weeks until the desired effects are achieved.
Let your doctor know if you’re experiencing dizziness, fatigue or other symptoms—this could signal that you’re taking a dose that’s too high for you.
Calcium channel blockers, including amlodipine (Norvasc) and felodipine (Plendil), are among the most commonly used drugs for high blood pressure. One potential side effect of these drugs is edema (fluid accumulation in the body)—and women tend to experience more of this edema than men.
My advice: Rather than taking a diuretic to manage edema, women (and men) who have this side effect might do better without a calcium channel blocker at all.
They can frequently switch to an ACE inhibitor such as lisinopril (Zestril), which also provides blood pressure-lowering effects—and does not cause edema. Alternatively, adding an ACE inhibitor to the calcium channel blocker can reverse edema.
Opiate analgesics, such as morphine, oxycodone (OxyContin) and hydromorphone (Dilaudid), have a greater analgesic effect in women.
In fact, women usually get pain relief from a 30% to 40% lower dose than that required for men. Women who do not take the lower dose are also more likely than men to experience side effects, including unwanted sedation.
My advice: Tell your doctor that you want the lowest effective dose. It can always be increased if you need more relief.
Low-dose aspirin is routinely recommended to prevent heart attacks and/or strokes. This benefit has been shown to occur in both men and women who have already had a heart attack or stroke but is less clear-cut in those who have not. Clinical studies have found that low-dose aspirin helps prevent stroke in healthy women ages 55 to 79 and heart attack in healthy men ages 45 to 79. Preventive low-dose aspirin may be especially beneficial for men and women with cardiovascular risk factors, such as high blood pressure, high cholesterol, diabetes, family history or smoking.
My advice: Men and women should discuss with their doctors whether they need low-dose (81-mg) aspirin to prevent a heart attack or stroke, especially since even small doses of aspirin increase the risk for gastric bleeding. Unlike some other drugs in which side effects are amplified for women, low-dose aspirin is less likely to cause gastric bleeding in women than in men.
