Drugs That Affect Women Differently

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

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

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

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.

READ Signs that YOU Are an Opiate Addict

 Opiates

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.

More Drugs That Affect Women Differently

Antidepressants

Men and women react differently to different antidepressant medications. Men seem to react better to tricyclic antidepressants, such as Amitriptyline (Elavil). However, regardless of the symptoms, women seem to respond better to selective serotonin reuptake inhibitors (SSRIs), with sertraline (Zoloft) appearing to be the most successful. This difference may be partly because women respond better of the serotonin-precursor tryptophan when given SSRIs.

No matter what antidepressants are prescribed, the lowest effective dose should be used, as a woman's higher proportion of body fat can lead to drugs staying in the body for longer, making side effects more likely.

Antipsychotics

Men generally exhibit more severe symptoms of psychoses (delusions, hallucinations, paranoia, and so on), and may require more prolonged hospitalisation. Women also respond better to treatment with "typical" antipsychotics (such as haloperidol) than men. Men may need up to twice the dosage to control their symptoms.

Anti-anxiety medication

Some anti-anxiety medications could be dangerous to women at normal doses. That's because women metabolise them quicker, causing them to feel the effects sooner. Women also take a longer time to process certain drugs. 

Benzodiazepines are especially dangerous because they dissolve into fat cells. Women have more fat, meaning that Benzodiazepines (like Xanax or Diazepam) can build to toxic levels in the body.

If you take anti-anxiety medication, and especially benzodiazepines, talk to your doctor about waiting longer to take a second dose.

READ Cognitive Behavioral Therapy: Best non-med treatment for anxiety and stress problems

Torsade de Pointes

In addition to the reactions above, women are also more prone to a very serious reaction called Torsade de Pointes. Torsade de Pointes is a type of ventricular tachycardia (where your heart beats more than 100 beats per minute; however, in Torsade de Pointes, the heartbeat is over 200 beats per minute). Patients with Torsade de Pointes usually have cold sweats, palpitations, and dizziness. It can cause sudden death.

Torsade de Pointes have been known to occur with: antidepressants, antipsychotics, antibiotics, and antiarrhythmics.

What Next?

We are becoming increasingly aware of gender-differences in reactions to medicines. Between 1997 and 2001, eight of the ten medications were removed from use by the FDA because they posed unacceptable risks to women. However, there's still a long way to go.

Women have up to an eightfold increase of drug-induced rash as a result of taking the antiretroviral drugs (to treat HIV), such as Nevirapine and Efavirenz). Women are also more likely to experience liver-disease as a result of taking antiepileptic drugs like Phenytoin.

Recently, the FDA has been conducting more research into drugs and sex-differences, but there's still some way to go before we fully understand the impact of gender.