Hey, Biology Nerd! I’ve heard that a lot of medicines that doctors give people are actually poisons. Why is my doctor trying to kill me?
I wouldn’t go so far as to say that doctors are “trying” to kill you, Sybil. Killing off clients wouldn’t be very beneficial to our business model, much less our reputation. That said, you are correct in that some common medications are indeed poisons. Many drugs are based off of deadly plant or bacteria components, poisonous in the wild but harnessed to help us. A friend in the pharmaceutical industry told me that every time they went on a trip they brought back native plants for the lab to experiment with. Millions of years of competition between bacteria, plants, and animals has led to the evolution of some pretty cool compounds. Botox, digitalis, and chemotherapy come to mind.
Botox is a fun one because the name is actually short for botulinum toxin. Remember hearing your grandmother talk about botulism? Yeaaaaaah, the same friendly bacteria that turns so many batches of homemade strawberry preserves into agents of chaos also makes your wrinkles disappear.* A shot of botox is a shot of the Clostridium botulinum exotoxin – “exo” meaning “outside” and “toxin” meaning “poison.” These are poisons that bacteria make and squirt outside of their cell bodies to hurt their hosts.
Botulinum, whether it’s working for us or against us, paralyzes muscles. Your brain tells muscles to contract by way of chemical signaling with molecules called neurotransmitters. Your nerve cells make some of these molecules in their cell bodies and transport them in little sacks down the axon (the long, skinny part of the cell that bundles with other cells’ axons to make the nerve fiber), and then they squirt them out onto the next cell. In this case, the neurotransmitter acetylcholine is popped like a zit right out onto the spot where the nerve plugs into a muscle, and that signals tells the muscle to contract. Botulinum toxin stops the nerve cell from attaching the sacks of acetylcholine to the outside of the axon. If you can’t attach the sack, you can’t “pop” it onto the muscle and so the muscle never gets the “hey, I need you to squeeze” message from the brain.
These muscles usually shrink over time, and your skin loses its elastic properties as you get older. So in these spots where the muscles get smaller, there’s extra skin covering less area then it used to – aka wrinkles. Botox stops this by keeping the muscles in their same chill state, so they don’t shrink away from the skin. But this is just the conventional use of Botox that most people are familiar with. Botox is a great drug that can help people with painful or unpredictable muscle spasms by paralyzing those specific muscles.
But Botulinum toxin is absolutely still a poison. When we use it in these carefully controlled ways, it helps us. When it’s accidentally eaten, it can be deadly. These days, the most common way of getting botulism is by eating either improperly sealed home-canned foods or raw honey. Babies are particularly susceptible to the latter, which is why you never give a baby honey unless you want it to develop “floppy baby syndrome,” in which they suddenly do a very accurate Raggedy Ann impersonation. The toxin can even paralyze their diaphragm, leading to suffocation. Once more for the folks in the back: DO NOT GIVE BABIES HONEY.
Let’s do another one. Digitalis, a drug that was once commonly used for heart failure, is also a poison. Digoxin, the generic drug name for Digitalis, is a man-made imitation of the poison of the foxglove plant Digitalis lanata. Digoxin works on the heart by disabling the sodium-potassium pumps that keep specific ratios of sodium and potassium on either side of the cell wall. This concentration difference is critical for signalling the heart muscle to contract, and getting rid of the concentration makes it impossible for the heart to beat very fast. Digoxin also builds up the amount of calcium in the heart cell. Calcium is the molecule that actually tells the muscle fibers to contract, and so having more of it increases the strength of the contraction. A slower heartbeat pumping more blood out is an excellent way to help a patient with heart failure keep their circulation moving. But Digoxin isn’t discriminating about where it binds to give these signals and will affect tissues that aren’t in the heart, leading to many rapid-voice-at-the-end-of-the-commercial side effects. Because of these problems, pharmacists have mostly replaced Digoxin with better and safer drugs, but it isn’t completely out of use.
Chemotherapies are nothing but poison. They stop the replication of cells in your body. See, cancer happens when the mechanism that tells cells to stop replicating breaks. Cancerous cells start multiplying like mad and take over the organ where they came from so that it can’t work anymore. Sometimes the cells get into the blood or lymph nodes and seed other tissues and organs with these crazy-fast replicating cells. Ordinarily, most cells in your body don’t replace themselves very frequently, if at all. The cells that do replicate often are skin cells and hair, blood cells, cells lining your GI tract — and cancer. Chemotherapy can’t target cancer specifically, so it hits all of the cells that reproduce quickly because cancer reproduces more often than most of the cells in your body. Some cells that are totally normal are killed off as collateral damage, which is why people on chemo usually lose their hair. They’re also vulnerable to infections because their white blood cells aren’t reproducing. In essence, chemotherapy is poisoning an entire body with the understanding that mostly cancer cells are going to die but all of the body’s cells are vulnerable.
The moral of the story is that poisons can be damn useful in the hands of doctors, but killing people is bad so they are used very, very carefully. This is also why you ALWAYS FOLLOW INSTRUCTIONS for drugs and don’t take them all willy-nilly thinking “if a little is good a lot is better!!” It’s a common saying around hospitals that “you can cure disease, but you can’t cure stupid.”
Or dead. We’re not that good at fixing dead.
In the meantime, take your poisons carefully and make an effort to not piss off your doctor.
*There’s a news anchor in my home town that I swear has had so many botox injections that he can no longer move his eyebrows, but I digress.
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