Death by Diphenhydramine: The Benadryl Bane

If you look at the autopsy data of pilots killed in aviation accidents the No. 1 drug found in their bloodstreams is diphenhydramine.

It is marketed as Benadryl® and a host of other brand names. You would think the most common killer would be something like marijuana, cocaine or other drugs of abuse, not that they didn’t pop up.

But no, it’s common, old, you-can-buy-it-at-any-drugstore Benadryl®. Its generic name is diphenhydramine and it’s been around since 1946. It is one of a number of medications known as antihistamines.

They work, as you’d imagine, by blocking the mediator histamine. Your body releases histamine in a number of inflammatory reactions such as infections or allergy reactions. Histamine release can cause swelling, itching, and redness.

That’s why antihistamines are so useful in controlling allergy reactions, hives, insect stings or the symptoms of an infection. Unfortunately, antihistamines have their side effects, diphenhydramine more than most.

It can cause drowsiness, forgetfulness, deterioration of vision and depth perception. Obviously, these side-effects can be and have been fatal if you’re trying to fly an airplane. It’s not too cool to drive a car or operate power machinery while taking diphenhydramine, either. So if it’s so deadly, how come it’s in so many over-the-counter and prescription medications?

The simple reason is that it is a very safe medication to take if you’re not trying to hand-fly an ILS (or drive a car or operate power equipment). As long as you know you are going to get drowsy, it is a great bedtime drug to take for what ails you.

And if you feel that crummy, you probably won’t object to checking out for a nap during the day. It seems to be well-tolerated by most kids and is in a large number of pediatric as well as adult cold, allergy and sleep medications.

A word of caution: It is felt that folks over the age of 65 might be more susceptible to the side effects of diphenhydramine, so it is not recommended for the “older” population.

Avoiding diphenhydramine can be tricky. It may be only one of several ingredients in a sleeping, cold or allergy medication. The name of the preparation might give you no clue that diphenhydramine is included. A quick Google search turns up the following preparations with it included: Kirkland Allergy Medicine, Allergy Relief, Western Family Sleep Tablets, Premium Value Sleep Aid, Phenwell AS, Pharbedryl, Banophen, Nighttime Sleep Aid, CVS Health Nighttime Sleep Aid, Bi-Electro, Equate Children’s Allergy Aleve PM, Original Formula Nighttime Sleep Aid, etc., etc. You get the idea! So what’s an airman with hay fever, a cold or insomnia going to do?

First of all carefully read the label. The ingredients are often in fine print on the back of the bottle, so break out your reading glasses

if you have to! If you do feel you have to take a diphenhydramine containing medication, the FAA wants you to wait for 60 hours after the last dose. Also you should be recovered from whatever prompted you to take the drug.

The wait period for diphenhydramine is longer than for most every 4-to-4, 6-hour dosed drugs. That’s because of its terrible record of involvement in aviation accidents. As a general rule of thumb, you should wait 30 hours after taking a drug that’s given every 4 to 6 hours and 60 hours after a medication that’s dosed every 12 hours before flying. In other words, wait five times the dosing interval before hopping into the cockpit. A couple of years ago, the FAA published “What Over-the-Counter (OTC) medications can I take and still be safe to fly?” (https://www.faa.gov/licenses_certificates/medical_certification/media/OTCMedicationsforPilots.pdf). I would definitely download it and paste inside

your medicine cabinet for reference.

The bottom line question whenever you are thinking about taking a medication, be it prescription or over-the-counter is this: “Am I well enough to fly?” If the answer might even possibly be no, kick back and do some hanger flying until you’re feeling better. If you do think you need something, make sure it’s OK with the FAA (and common sense) to take while flying. After you’ve taken it, make darn sure your symptoms are well controlled and you are not having side-effects from the drug.

Fly wisely. See you next month.

As always, comments, questions and suggestions are welcome: jdlakinmd@gmail.com.

Also, we’ve moved our office to Airlake Airport’s FBO (KLVN)! Call 952-469-4414 for a flight physical appointment.