Erythromycin is an antibiotic. This much is true. It is active against mycoplasma and against ureaplasmas, but is very poor at actually eradicating them. It also stimulates motilin receptors in the bowel, that is why it increases bowel activity, and may cause diarrhoea in adults and older children taking it. It may also be the reason behind the development of pyloric stenosis in infants who get erythromycin, one of the serious potential complications.
Allergy to erythromycin on the other hand doesn’t seem to occur, I am sure there is a good reason for this, but I have no idea what it might be.(ask an immunologist if you really care)
Erythromycin has been studied as a treatment for feeding intolerance, this is interesting, (at least for a data nerd like me) as the outcome in many studies has depended on things like volumes of gastric residuals, which themselves are largely useless as outcomes. So if you measure gastric residuals, and determine your feeding advancement on their volume, you can advance feeds faster on erythromycin than on placebo. In very immature babies there is much less evidence of efficacy, and we know nothing about the embryologic development of motilin receptors. So it might not work in those babies. For any other important clinical outcome as far as I can see there is no evidence of benefit, such as necrotizing enterocolitis or duration of hospital stay.
There are a few systematic reviews out there, on Erythromycin for feeding intolerance in the preterm, including one by my friend Sanjay Patole (who also did one of the trials), he is editing the book for which I am writing this chapter on FGER (that is F****** GER, what I have come to think of it as, during the re-writing of this chapter!) Anyway, there is not a single study ever published according to my literature searches, on the use of erythromycin for reflux (FGER) in the newborn.
It seems that there are people out there using it for reflux, however, which is very depressing. Please don’t.
As well as being associated with pyloric stenosis, erythromycin increases QT duration, due to an effect on the inward potassium channel in the heart I(Kr), and can cause lethal arrythmias. Also, no other prokinetic agent has ever been shown to improve reflux, so it seems very unlikely that erythromycin will either.