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Motion Sickness – What You Need to Know

motion sicknessGreek Physician Hippocrates first described the principle symptom of motion sickness, (nausea), most frequently occurring during boat travel. Derived from the Greek word for ship (naus).

It happens to the best of us. Some of you may not have experienced it in a long time; however, we all can agree how miserable it is to get motion sickness.

Why does it occur?

It turns out that this question is very complex. The best explanation is called “Sensory Conflict Theory.”

The brain receives certain inputs to help perceive motion and spatial orientation of the head.

Not to get too complicated think of it as 3 senses that tell your brain about motion and orientation.

  • Vestibular System (inner ear-semicircular canal and otolith organs)
  • Visual (what are you seeing)
  • Somatosensory system (signaling between muscle and joints gives your brain understanding of your body’s position)-not as important

inner ear

When these signals aren’t all saying the same thing you get motion sickness

Example: You are in the Cabin of a boat (all visual cues think you should be stationary-all the furniture is fixed in place) however your inner ear (essentially an accelerometer and gyroscope) says you are moving. These signals don’t match up so you get motion sickness.

Who gets motion sickness?

  • Almost everyone. Although there is a wide degree of susceptibility
  • Sex: Woman more than Men
  • Age: Children less than 2 years of age are usually resistant. Susceptibility decreases through adulthood
  • Migraine sufferers: More susceptible to motion sickness (Unfair)
  • Psychological: If you are thinking about it, you are more likely to get motion sickness (Don’t you love it when people say don’t think about it!)
  • Frequency: Low Frequency motion (bobbing in the ocean) more likely to cause motion sickness than higher frequency movements

Symptoms

Hyperventilation, nausea, burping, increased salivation, warmth, and sweating, and a general feeling of “crap”- yes I said it.

Treatment

I’m sure you have heard keep an eye on the horizon. So why is this true?

You want to match your visual cues with what your vestibular system (inner ear) is sensing. The vestibular system is set to “earth fixed frame of reference.” So looking at horizon or landmasses helps these match up and send the same messages to the brain.

Important Note: Looking at horizon or land masses from outside deck is best, avoids the confusing visual cues seen inside the boat while trying to look outside.

sea sickness

When it comes to treatment prevention is best. It’s harder to stop motion sickness once it has already started.

Medications

This may be a little dense but I think its important to introduce you to these medications.

How do they work?

  • Most of them suppress the signals from vestibular system to your brain so you don’t get conflicting information when compared to your visual cues

Medication Classes That Work ( AKA: What type of drug receptors are we targeting)

  • Antihistamines 1st generation
  • Anticholinergic
  • Antidopaminergics
  • Sympathomimetics
  • Benzodiazepines

I know some of you reading this are asking me what did you just say. Lets go through each type of medication class and hopefully you recognize some of the medications and I bring you back in on this- Don’t give up on me just yet.

Antihistamines (H1-1st generation antihistamines)

  • Dimenhydrinate (Dramamine)-Available as chewable
  • Diphenhydramine (Benadryl)
  • Chlorpheniramine
  • Meclizine (Bonine or Antivert)
  • Cyclizine
  • Cinnarizine (Not Available in USA)

Things to Know

  • There is something called the Blood brain barrier: a fatty membrane that acts as a filter to what medications can go into the brain what cant. If medications are also fatty (lipophilic) then they get through. If not they don’t. 1st generation antihistamines listed above go through (that’s why they make you sleepy) and also the reason they work (need to block signals to the brain)
  • They do make 2nd and 3rd generation antihistamines like ex: loratadine (Claritin). These do not cross the blood brain barrier, thus aren’t sedating, and aren’t effective in preventing motion sickness. Ex: if you are a captain and have allergies than you want to take a non-sedating antihistamine so you can still do your job adequately

What is the best one?

  • Really not great evidence to say a specific one is better than another. Some may be less sedating than others (Dramamine), however, they are all effective. You may hear folks who go to Mexico say oh Cinnarizine is the best. I don’t have any evidence for this but margaritas are better in Mexico so…… You get the idea. They are all playing defense on the same type of receptors in the brain.

Side Effects

  • Sedation (most common), blurred vision, mouth dryness, and, in the elderly, confusion and urinary retention.

Anticholinergic

  • Scopolamine Patch (transdermal)
  • Scopolamine Oral (Scopace)

motion medicine

Things to know

  • The transdermal patch lasts 72 hours and appears to be less sedating (popular option)
  • From the studies available it appears to be one of “the best” drugs we have
  • If your patch doesn’t have good contact with your skin its not going to work

Side Effects

  • mouth dryness (most common), sedation, blurred vision, and, in the elderly, confusion and urinary retention.

Antidopaminergic

  • Promethazine (Phenergan)-Used to Prevent or Treat
  • Metoclopramide (Reglan)- Less evidence out there saying it works

Things to know

  • Promethazine (Phenergan) Used for prevention and treatment of motion sickness
  • Promethazine (Phenergan) comes in Pill form or can be given as an IM (intramuscular shot)- ex: if on a cruise ship and very sick, you will likely get this shot since you cant handle a pill
  • Very sedating (night night)

Side Effects

  • Sedations, Extrapyramidal symptoms (google this to learn more)

Sympathomimetics (Think of these as stimulants)

  • Ephedrine, amphetamines, caffeine, etc…

Things to know

  • Not an area to mess around in but their have been benefits of some of these drugs in preventing motion sickness
  • Utility has mostly come from taking these medications to combat the sedation from the above medications so performance is not effected
  • Example: There are some studies that have shown caffeine + promethazine (Phenergan) were even better than the patch, however as you could imagine taking caffeine pills and motion sickness pills has its health risks. So if you are thinking why aren’t we given this recipe, that is why
  • This area has been looked at greatly with folks that have jobs that cannot be compromised by motion sickness (Military, Coast Guard, etc…)

Benzodiazepines (Ativan, Xanax, etc)

  • They have benefit but too sedating to even consider

You should be picking up on the theme that the majority of the drugs are sedating

Lets take a look at some other options (For the folks saying what about those wrist bands, or ginger, etc.. This is for you)

Ginger

  • There are studies, done on naval cadets, where it showed to have benefit as a pre-treatment method. These folks were given 2 grams of ginger. So for the folks who chew on a small piece of ginger, have a ginger ale, etc… Not entirely sure how much that is helping but there is proven benefit in ginger nonetheless
  • Mechanism of how it works to prevent motion sickness is up for debate: is it a stomach motility deal or does it work on receptors in the brain (Great discussion on the way out to the fishing grounds)
motion bands
Photo credit: http://zenparent.in/parenting/8-quick-acupressure-healing-points-for-your-school-going-kids

Acupressure

  • Pressure at the P6 acupressure point is what we are talking about.
  • What do the studies show? Some show it may have benefit and some did not show any benefit.
  • So…. What does this mean? Well in these studies its hard to get true randomization since people know if there is pressure on their arm vs not. Ex: Its not like giving 2 people pills, one being nothing and another being a drug and they don’t know what they got. Does this make sense?
  • So generally speaking, it may work. Everyone has friends that swear by it. It cant hurt to try and see if you are a responder

Magnets

  • No worthy studies that have shown this modality to be used to prevent motion sickness
  • Translation: I wouldn’t go down this route

sea sick

Summary

  • Motion sickness is thought to be due to conflicted signals to the brain on perceived motion
  • Nearly everyone is at risk with enough stimulus
  • Keeping your visual signals the same as your vestibular signals helps (Look out at the horizon or land masses)
  • The majority of medications above help prevent motion sickness from happening, however sedation is a big issue
  • Alternative treatments with Ginger or Acupressure may have benefit

This information is not to aid in self-treatment but to help you understand why motion sickness occurs, the various treatments available, and their side effects. I write this in the hope that it will aid in your dialogue between you and your physician.

As always please feel free to contact me with stories, suggestions, or requests for future articles. Thank you for reading.

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Brad Genovese. I was born and raised in Laguna Niguel, California. He has been greatly blessed to have incredible parents that introduced him to sport fishing, hunting, and travel at an early age. Growing up he spent many summers fishing and diving the Sea of Cortez. Brad says, “Although my entire family is in the business world I decided to break away and pursue a career in Medicine. I attended Cal Poly San Luis Obispo, CA where I received my BS in Biochemistry. After this I went off to New Orleans, LA and received my MD at Tulane Medical School. I am currently back in California, where I am a licensed physician and working towards completing my training in General Surgery at UCLA. Although a busy and demanding career, it has its moments that make it all worth it. Whenever I am not working I try to get out on the water to catch some fish and spend some quality time with family and friends.“