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Antibiotics for SIBO

A variety of antibiotics are used to treat small intestinal bacterial overgrowth. Historically cyclical courses of various antibiotic including, tetracyclines, trimethoprim and amoxycillin or ciprofloxacin have been used, however this may significantly adversley impact the microbiome, with unforseen consequences.

More recently rifaxamin has been widely used since it has a relatively narrow spectrum of activity and is not significantly absorbed. This drug is not as widely available as it might be for this indication within the UK, in part because of its significant cost (over £1000 per annum in longterm annual use)

Tetracyclines; Oxytetracycline

Tetracyclines are a class of antibiotics derived from a bacterial class known as Streptomyces. They have activity against both gram positive and gram negative organisms, but in recent decades have become less effective because of increasing bacterial resistance. They can be used in syphilis, Lymes Disease and rickettsial disease. Historically they have been used to treat bacterial overgrowth but because they remain in the gut a number of bacterial organisms have become resistant to them.

Side-effects include nausea and diarrhoea. They should be avoided in pregnant women and young children since they appear to persist in bones and teeth if they are given during development of these tissues.



Is an antibiotic that was developed relatively recently (2004) and has been shown to be largely unabsorbed by the gut. As such it may have particular benefits for treating infection within the gut or the gut wall since it does not appear to cause much in the way of systemic side effects. There is evidence for its use in Small intestinal bacterial overgrowth, hepatic encephalopathy and non-constipation predominant irritable bowel syndrome, however in Western Europe and North America the price of Rifaximin is a bar to it’s wider use.

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