If only the world agreed with our intent 100% of the time.

Side effects are unintended or secondary effects of drugs. Some are good, surprising, or beneficial. Some are neutral, some are a little bad, some are medium-bad and some are weapons-grade bad. Like, kill you bad.

The good ones can be rather fun, or at least novel. The diuretic furosemide (commonly known as Lasix), long the mainstay of treating heart failure in both man and beast, is also a bronchodilator – it opens up your airways. Not only does it efficiently get the water out of your lungs and help you to breathe easier when your heart is failing, you get the extra bonus positive effect of some bigger airways to breathe through. That one is win-win. (Except if you are using the response to furosemide as a test to see how likely heart failure is – then the easier breathing brought on by the side effect can be a tad confusing.)

The neutral ones are just a curiosity. If your doctor prescribes you a new drug for your pleurisy and your left pinky toe develops painless cheetah spots, well, you’ll have something to talk about at garden parties, but otherwise be just fine. No harm, no foul as they say in badminton.

The medium-bad ones are the ones that we keep in our wheelhouse and warn owners about when we prescribe the medication. Sticking with the furosemide example, owners will always note that their pet develops an intense thirst and leaves many more little clumps of litter in the litter box or trips to the fire hydrant while they are on it. This is commonly seen and expected and we always let owners know about it. Or mild and transient diarrhea while on antibiotics. It’s nearly de rigeur, and usually some notice about it goes in the discharge instructions so we don’t get any nasty phone calls about Fluffy ruining the orange shag rug.

The weapons-grade bad ones just suck. They are sneaky, unpredictable, rare, and cause no end of sorrow to pets, their owners and veterinarians. They are like poisonous snakes hiding in the lovely and well-tended bushes of an otherwise orderly garden of medical certainty.

Odds are if you prescribe medication for long enough, one of these snakes is going to bite. We never want it to happen, we’ve taken an oath that we will only help, never hurt (well, actually, I’m lying there. Only MDs have that as a part of the oath and then only in some forms of the Hippocratic Oath. The oath that vets swear to doesn’t mention the concept). But surely, our intent is to help.

So when one of these snakes sneaks out of the bushes and sinks its fangs into your tender and unsuspecting ankle, you know that sadness and despair are baked right in.

The problem with the medium-bad and weapons-grade bad side effects is twofold. The patients are less well-off than we intended, and the pet-owners immediately brand you as some sort of evil troglodyte for prescribing such a horrific medication in the first place. The looks and angry emails and conversations all take on a faint air of how could you do such a thing, as if the side effect was the main reason that we gave the drug, or we somehow knew this would happen, we just didn’t tell anyone.

My experiences with medium-bad side effects are way too many to count. They’re just part of the cost of doing medical business and thankfully most pet-owners understand and roll with it when an unintended consequence crops up, as long as it’s not that severe. Preparation is key, though. Letting someone know that a little diarrhea is around the corner when you prescribe an antibiotic makes you look like a clairvoyant. It’s usually appreciated.

I have had a few instances of the weapons-grade badness happen, and only one really sticks in my mind. It was after a prescription of the antibiotic amoxicillin, among the most commonly prescribed medications in the world. I can’t remember what it was for, but surely it was something garden variety, and, to be honest, something that probably would have cleared up on its own, given time. (Many, if not most, antibiotic prescriptions are dispensed due to the immense pressure to “do something” and are for conditions that are known as “self-limiting” and really need no therapy other than time). 

This poor dog, who may have had an infected toe, a dalliance with dermatitis, or some such, developed one of the most dreaded of all side effects: toxic epidermal necrolysis, or TEN.

It’s as bad as it sounds.

When you have TEN, your skin essentially dies off – all of it. And you have skin in places you don’t even really think of as having skin; your mouth has a covering of epidermis, which is a form of skin. Your intestines have a layer of epithelium, which is in essence skin. With TEN, it’s all gotta go. It’s fire sale time when it comes to skin, and we need a cleanup on aisle five.

This is really not a topic you should ever do a Google image search for.

Welcome back.

I don’t recall that much about this poor dog’s sad demise, except that it was slow and painful and I spent the entire time apologizing to the family for something that was both not my fault and also totally my fault. Luckily, they were understanding, as well as devastated and believed me when I said I had prescribed this medication thousands of times with no more ill effect than a little diarrhea. Their poor dog just had the galactic bad luck to have his number come up that day. Powerful pain medications were needed and I hope to this day that his suffering was as alleviated as I could make it.

Every prescription I wrote for amoxicillin after this incident made me stop and think “Is this really needed?” and I wonder if I perhaps held back on writing prescriptions for it that were actually necessary, but that I was just too gun-shy from my one-in-a million with TEN encounter to do it. There are so many ways to feel guilty about this episode.

If you’ve ever had a side effect from a medication, I do hope it was a mild one. It takes a special kind of person to forgive and forget after one of the more severe ones, but they really are the lightning strike of the medical world in most cases. I couldn’t save the TEN dog, and I will always feel bad about that, but I am thankful that the owners were understanding and kind, and that I haven’t had any more since then.