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Research suggests that women are up to 75% more likely to experience side effects than men taking the same dose of medication. But why is that?
Research into sex differences in medication absorption is a new field. Until the 1990s, all medications were only tested on men (at least in the US). This means there is little evidence of their safety and efficacy in women. New evidence suggests that some medication may be more potent in women, making side effects more likely.
Women take longer to digest food, and produce less gastric juices. Women take longer to digest medications that ought to be taken on an empty stomach if they have eaten. Women typically weigh less than men, and store more fat (which trap medications in the body), and this body composition also contributes to problems. Additionally, women tend to have a slower metabolism, which means it takes longer for medication to clear the system.
In 2013, the FDA released the first gender-specific dosing instructions for any medication. After finding that Ambien (a commonly prescribed sleeping medication) is doubly-potent in women, and is removed from the system more slowly, it ordered that Ambien doses should be lowered from 10mg to 5mg (immediate release) and from 12.5mg to 6.25mg (extended release).
Aspirin is commonly prescribed after a cardiac event such as a heart attack or stroke to prevent future reoccurrence. However, while men who take Aspirin had fewer heart attacks, women didn't show any benefit from taking Aspirin compared to taking a placebo.
However, there is some good news. While women taking Aspirin didn't experience reduction in heart attacks, they did experience fewer strokes. Men still experienced strokes at the same rate.
Beta blockers are used to lower the blood pressure. Women notice their blood pressure and heart rate drop particularly low with Beta Blockers, especially when taking Metoprolol. This effect is enhanced when exercising.
It's recommended that women using Beta Blockers closely monitor their heart rate and blood pressure.
Digoxin is a medication that is sometimes used in the treatment of heart disease. A 2002 study by Krumholtz and colleagues found that the use of Digoxin by women, though not men, increased the risk of death by heart failure.
It is recommended that Digoxin is used with caution, if at all, in women with symptomatic heart failure (heart failure in which there are symptoms such as breathlessness, fatigue, etc.). Prior to that stage, women require a lower dose.
Women receive a greater pain relief from opioid analgesia. Men need up to 40% more morphine to receive the same amount of pain relief.
However, women may be more likely to use pain relief. Due to oestrogen, women have lower pain tolerance. Women are also more likely to struggle to quit opioid painkillers, especially in the middle of their cycle. In the middle of the menstrual cycle, glucose in the brain (which governs self-control) is lower.