Erythromycin

Erythromycin sits in the macrolide group with azithromycin and clarithromycin. It is used for bacterial infections of the ears, lungs, sinuses, throat, skin and reproductive organs, and sometimes before dental work to protect the heart lining of people prone to infection there. PockDose sells it among its antibiotics as Erythromycin tablets, 250mg and 500mg.

What erythromycin treats

Chest infections such as bronchitis and pneumonia, sinus and ear infections, sore throats, skin infections and some infections of the reproductive organs all respond to it when bacteria are the cause. Colds and flu are viral, and erythromycin does nothing for them — antibiotics taken when they are not needed help resistant bacteria build up, which makes later infections harder to treat. It is not the right antibiotic for every infection either; whether it fits depends on the bacteria involved.

How erythromycin stops an infection

Erythromycin blocks the ribosome, the part of a bacterial cell that builds proteins, so the bacteria cannot grow or divide and the body's own defences can deal with what is left. Human cells build their proteins a different way, which is why the tablets act on the infection rather than the tissue around it. The process starts with the first dose, but symptoms often take a day or two to ease.

Fitting a course around your day

Plenty of courses call for three or four doses a day, about six to eight hours apart (say breakfast, mid-afternoon, evening and bedtime); others are twice daily. Swallow each tablet whole with a full glass of water, because chewing or crushing changes how it is absorbed. Eating is optional: the tablets work on an empty stomach too, and a slice of toast can help if you feel queasy. Carry on until the box is finished, since stopping when you feel better lets the infection return.

Side effects worth knowing about

Nausea, vomiting, diarrhoea, stomach cramps and going off your food are the usual complaints, and they often settle after the first day or two. A swollen face or throat, wheezing or difficulty breathing points to a severe allergic reaction, which needs urgent treatment. Rarer problems include liver effects — yellowing of the skin or eyes, dark urine, pale stools, pain below the right ribs or unusual tiredness — and a fast, pounding or irregular heartbeat. Very watery or bloody diarrhoea can appear during the course or up to two months after the last tablet.

Other medicines to think about

Erythromycin slows the liver's breakdown of several common medicines, so they can build up to higher levels than usual. The best-known examples are the blood thinner warfarin, digoxin, the epilepsy medicine carbamazepine, the asthma medicine theophylline and statins such as simvastatin. Simvastatin is normally paused while a course runs, and erythromycin is not taken with migraine medicines containing ergotamine. If you take any of these regularly, the overlap is worth knowing about before the course starts.