I was prescribed erythromycin (an antibiotic) for a skin infection. To my surprise it helped both the skin infection and (temporarily) helped a totally unrelated, extremely painful, long-term pain problem I have that doctors assume is gut-related. In reality they have no idea what the actual problem is, and I think it is probably seen as being an MUS (therefore is imaginary, therefore no further investigation will be done), and so I am left to just get on with it - although I did start getting prescribed pain-relief two or three years ago.
I assumed as a result of this unexpected improvement with erythromycin that my pain must be caused by an infection. But two doctors have disagreed with me. Since I've had no further tests I assume their disagreement is based on the day of the week or the direction the wind is blowing.
At the time this all happened I was seeing a gastroenterologist about something else. When I told her about the massive reduction in pain I got from taking erythromycin she told me that she didn't believe that I had an infection. Instead she decided that I suffered with gastroparesis. This was because erythromycin is a "prokinetic agent" as well as an antibiotic :
https://en.wikipedia.org/wiki/Prokinetic_agent
A gastroprokinetic agent, gastrokinetic, or prokinetic, is a type of drug which enhances gastrointestinal motility by increasing the frequency of contractions in the small intestine or making them stronger, but without disrupting their rhythm. They are used to relieve gastrointestinal symptoms such as abdominal discomfort, bloating, constipation, heart burn, nausea, and vomiting. They are used to treat a number of gastrointestinal disorders, including irritable bowel syndrome, gastritis,[1] gastroparesis, and functional dyspepsia.
Since doctors aren't happy to prescribe antibiotics all the time, the gastroenterologist insisted I try a different prokinetic agent, and the one she chose was metoclopramide. If it worked then it would, allegedly, prove I had gastroparesis.
Unfortunately, what I didn't know is that metoclopramide has several names and one of those is Maxalon. And back in the 1990s I had reacted severely to Maxalon after I was injected with it as an anti-emetic during surgery. I had developed
extrapyramidal symptoms and had arms and legs which I couldn't control and they were twitching and spasming like crazy until the injection wore off.
The gastroenterologist prescribed metoclopramide in tablet form, so the reaction wasn't so quick as the injection. Completely unaware of what was about to happen, the first day I took three of the tablets (the dose I was prescribed), and I became a totally reckless driver which is totally out of character. I was lucky I wasn't done for speeding. My husband noticed other changes in my personality and the way I was acting. The second day I didn't feel well so I only took one tablet. The third day I took one tablet as well - and that was the last one I took and will ever take. The extrapyramidal reactions kicked in and I could NOT stand still. I paced and twitched and spasmed and jerked and I could not sit still either. I also became suicidally depressed in no time flat and debated running in front of a bus or a train, because if I had to spend much more time like this I wanted to kill myself. In the end I saw a duty doctor at my local surgery and she prescribed an antidote. It got rid of the worst of the problem in about 3 days or so, but I didn't feel "normal for me" for several months. (My doctor didn't believe it took several months to feel back to normal, but doctors never believe a word I say unless they can see the problem with their own eyes.)
I've done some research since then and have discovered that metoclopramide is a dopamine antagonist and that causes my reaction. I suspect that either I have low levels of dopamine or have fewer dopamine receptors than normal. And that may well be because I have hydrocephalus which is believed to have developed in childhood or earlier.
For people who don't suffer from dopamine problems there are 13 prokinetic agents they could try listed on wikipedia. Unfortunately, I still have no clue at all whether I have gastroparesis or not.