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March 8, 2017

How Do EpiPens Work?

This is the latest post in my #BrainBits series, where I'll answer your burning neuroscience questions in 60 seconds or less. If you have a question you'd like me to answer, you can e-mail me, tweet me, or submit your questions anonymously here.

EpiPen has made a splash in the headlines in recent months. Last summer, the pharmaceutical company Mylan drew widespread criticism when it was revealed that a 500% price hike had been placed on the epinephrine autoinjector. After Congressional investigations, Mylan agreed to introduce a cheaper generic version of the drug, as well as fund programs to help patients afford the costs.

An EpiPen, with its safety cover. Source: Tokyogirl79 (Wikimedia Commons)

But the damage has already been done: since the beginning of 2017, physicians have been prescribing alternatives to EpiPen at a rate 6X higher than in 2016. Without insurance, a generic version called Adrenaclick costs just $10 for a two-pack at CVS.

A young boy with anaphylaxis. 
Source: James Heilman, MD 
(Wikimedia Commons)
So how do EpiPens, and other brands of epinephrine autoinjectors, work in the first place?

Millions of people keep epinephrine autoinjectors on hand due to their risk of anaphylaxis. Anaphylaxis is a serious type of allergic reaction — most commonly to particular foods, animal stings or bites, and medications — that can start within minutes of exposure to the allergen. Symptoms include shortness of breath, throat or tongue swelling, vomiting, lightheadedness, and a drop in blood pressure.

Why such a severe reaction? In response to the the allergen, inflammatory mediators such as histamine cause contraction of smooth muscles (such as the lungs), blood vessel dilation and fluid leakage, and changes in heart rate. A person can die from anaphylaxis if their heart stops beating, or if they are unable to breathe due to swelling of the airway.

EpiPens work by rapidly injecting a dose of epipinephrine (also called adrenaline), which reverses the effects of anaphylaxis.

Epinephrine. Source: Roland Mattern (Wikimedia Commons)
Epinephrine, which plays an important role in our fight-or-flight response, relaxes the smooth muscles of the airways and lungs, and rapidly increases blood pressure by constricting blood vessels. (It's the same hormone that makes us feel like we can run a marathon when, instead, we have to sweat through a public speech to a large, scary audience.) The pen is injected directly into the thigh muscle, as the intramuscular route is faster than subcutaneous administration (like how insulin is delivered).

Have you used an epinephrine autoinjector before? What was the experience like? Let me know in the comments.

February 16, 2017

Why Does Drinking Milk Ease the Pain of Eating Spicy Food?

This is the latest post in my #BrainBits series, where I'll answer your burning neuroscience questions in 60 seconds or less. If you have a question you'd like me to answer, you can e-mail me, tweet me, or submit your questions anonymously here.

You can find me with a plate of hot wings, and a glass of milk.
Source: falovelykids (Pixabay)
I'm pretty wimpy when it comes to eating spicy foods — but if I must indulge in some peppery Chinese food or a plate of hot wings, you'll surely see a glass of milk close to my reach.

Chili peppers contain an active component called capsaicin, which is part of the vanillioid family (the same family that includes the vanilla bean). Capsaicin binds to a receptor called the vanilloid receptor subtype 1 (TRPV1).

While TRPV1 receptors are found in several different organs throughout the body, activation of the TRPV1 receptor on the tongue produces the sensation of heat or abrasion, causing that characteristic burning sensation. Eating a chili pepper does not actually cause a chemical burn — but it certainly feels like it.

So why does milk soothe the savage serrano?

The chemical structure of capsaicin (below) reveals a long hydrocarbon tail, shown in black (carbon) and white (hydrogen):
Chemical structure of capsaicin. (Source: Jacopo Werther/Favourites/Chemistry, Wikimedia Commons)

That hydrocarbon tail means that oily or soapy compounds can act as a detergent to dissolve capsaicin, but water cannot. It's similar to how you can't clean grease off of a cooking pan simply with water, but dish soap will get the job done.

Source: Unsplash (Pixabay)
Milk from mammals contains a protein called casein (the same protein which creates curds in sour milk). Casein is a lipophilic (literally, "fat-loving") protein, which means that it acts as a detergent on capsaicin, thanks to that fatty hydrocarbon tail.

Alcohol also dissolves capsaicin well (wings and beer, anyone?), although its concentration in most alcoholic beverages is often too low to have much of an effect. (On the other hand, casein represents roughly 80% of the protein in cow's milk.)

But remember: it must be mammal's milk! Plant-based milks — such as soy, rice, coconut, or almond — do not contain casein.

Fun fact: Interestingly, in birds, the TRPV1 receptor does not respond to capsaicin, which means that the seeds of chili pepper plants can be dispersed widely. Biologists believe that some species of peppers, such as ghost peppers, have evolved to contain such high levels of capsaicin in order to deter animals from eating them — unless they are also able to help disperse the seeds!

Learn more about the Scoville Scale and how spiciness is quantified here.

Do you have a favorite home remedy for combating the pain of spicy foods? Let me know in the comments!

January 11, 2017

Does the Mercury in Vaccines Cause Autism? What's the Safest Immunization Schedule for Infants?

This is the latest post in my #BrainBits series, where I'll answer your burning neuroscience questions in 60 seconds or less. If you have a question you'd like me to answer, you can e-mail me, tweet me, or submit your questions anonymously here.

With the recent news of President-Elect Trump's talks with Robert F. Kennedy, Jr. to potentially head a new commission on vaccine safety and scientific integrity, many in the scientific and healthcare communities are understandably rattled. Kennedy is a well-known skeptic of vaccine safety, and has previously described the vaccine/autism allegations as such:

“They get the shot, that night they have a fever of a hundred and three, they go to sleep, and three months later their brain is gone. This is a holocaust, what this is doing to our country.”

Source: James Gathany, Judy Schmidt, USCDCP
Mercury is toxic to the human body. It's important, however, to understand how the mercury present in immunizations is different than the mercury in, say, the scary old thermometer in your medicine cabinet.

Thimerosal is a vaccine preservative. Since the early 20th century, small amounts of thimerosal have been used in vaccines to prevent the growth of fungi and bacteria. Thimerosal is mainly composed of ethylmercury. When we hear concerns of mercury toxicity (for example, with the consumption of fish), we are primarily concerned about the compound methylmercury.

Methylmercury (left) and ethylmercury (right). Image source: Wikimedia Commons (public domain)

Ethylmercury is metabolized and excreted by the body much faster than methylmercury (half-life of 1 week vs. 6 weeks), meaning methylmercury is more likely to "build up" in the body. You consume higher, longer-lasting, more concerning doses of mercury when you eat a serving of fish than when you get a vaccine.

Many independent epidemiological studies over the last two decades have concluded that the low doses of thimerosal in vaccines are not harmful to infants, and the compound is not present in routine childhood vaccination schedules in the U.S., E.U., and several other countries. All this said, the current scientific consensus is that there is no compelling evidence linking vaccinations and autism; mercury poisoning does not resemble autism, and rates of autism diagnosis continue to rise despite the removal of thimerosal in many vaccines.

Furthermore, there is no evidence to suggest that the American Academy of Pediatrics' recommended immunization schedule is harmful, or that young children's bodies can't "handle" it. Spacing out vaccines only increases the amount of time by which children are vulnerable to contracting vaccine-preventable diseases. The parents' choice to delay their children's immunizations is what caused the measles outbreak in Disneyland in 2015, with nearly 150 cases.

It's estimated that the MMR (measles, mumps, and rubella) vaccine has saved 17.1 million lives worldwide since 2000. Herd immunity is important for the health of the entire community, as not all children can be vaccinated or will respond satisfactorily to immunizations.

Further reading: