QUESTION posted on 02/09/2021: (Answer posted below)
If there is one thing I know as an equine doctor, is you don’t mess around with the brain and nervous system, and you don’t mess around with eyes. These problems deserve immediate attention, these organs simply don’t heal well.
Of course, you know my husband refused to listen. Instead he asked if it would be okay if he used Jewel’s eye medication which we were coincidentally using to treat her eye for a scratch at the time. (For the record, I did tell him absolutely not.)
The following day, he was complaining of blurred vision and anisocoria. (Yes, he still refused to go to the doctor, and yes, I about lost my marbles.) Finally, after using the sink and noticing the vial of this ophthalmic medication sitting on the edge, I had left it on the sink the previous day.
My husband claimed he didn’t use the horse’s eye medications.
What effect does this drug have, that let me know he was lying? (hint: it was used once as a fashion statement for this reason.)
Get a bonus chance if you can tell me the name of the plant from which it derives.
(No, he never went to the doctor, and yes his eye is fine now.)
ANSWER:
The atropine pictured above causes dilation of the iris – you ophthalmologist may use this drug to this day for precisely this purpose – in equine medicine it is a staple in treatment of various ocular conditions from corneal ulcers to uveitis. Another very common use for atropine in veterinary medicine is to elevate heart rate during anesthesia.
Atropa belladonna, commonly known as Deadly Nightshade, is the plant from which Atropine derives. The
Latin name means ‘beautiful lady,’ which was its actual claim to fame: as a fashion statement – women would apply drops derived from this plant in their eyes to dilate them because at the time that was the in vogue thing to do. It’s a plant that grows in France, so you’ve probably never actually seen it, but you probably have seen it’s ‘cousin,’ Jimson weed (Datura stromonium, also a part of the Nightshade family), growing in pastures. Both plants have several toxic components in addition to Atropine – but thankfully, there is a reason it seems to grow so well in eaten down, trampled pastures and dry lots, and that’s because livestock don’t really mess with it unless starving due to it's strong odor and foul taste - livestock are probably more likely to consume it if baled in hay or it ground down and mixed in feed such as silage or haylage. (If you want more information you can check this link out on the Missouri Department of Conservation website!- I also really liked this overview of the plant and it’s toxic symptoms from Cornell - and Colorado State has some nice photographs of it.)
Dosis sola facit venenum As with many other pharmaceuticals and toxins alike, atropine, while a valuable pharmaceutical when administered in appropriate amounts and modalities, can also be quite toxic. Ironically, atropine is also used as a part of some treatment regimes for other toxicosis including organophosphate and carbamate insecticide poisoning. These properties are biologically what we would call ‘anticholinergic’ effects – I’m not going to get into the details of what that means other than to say it has to do with the sympathetic and parasympathetic actions of your nervous system – the unconscious part of your nervous system that allows for your body to function and causes your ‘fight or flight’ and ‘rest and digest’ bodily functions, respectively. So, you can imagine, if you have a toxin that causes ‘cholinergic’ effects, a compound that causes ‘anticholinergic’ effects might be valuable for trying to sustain life. Of course, by itself it can also be deadly. Atropine toxicosis can cause dilated pupils, an elevated heart rate, heart arrythmias, diarrhea, fever, in humans mania, disorientation, and hallucinations are noted. Death is caused mainly by respiratory paralysis – i.e. suffocation – though, cardiovascular collapse or a cardiac event are also dangerous complications. (This was a nice little synopsis of Atropine toxicosis. They have some nice citations at the end for my more scientifically oriented folks reading.)
Thanks for playing!
Sarah L Rhoades, DVM