Antibiotic-associated diarrhoea is estimated to occur in 2% to 25% of people taking antibiotics, depending on the antibiotic used (NICE clinical knowledge summary on diarrhoea – antibiotic associated).
About 10% of the general population claim to have a penicillin allergy; this is often because of a skin rash that occurred while taking a course of penicillin as a child. Fewer than 10% of people who think they are allergic to penicillin are truly allergic. See the NICE guideline on drug allergy: diagnosis and management for more information. People with a history of immediate hypersensitivity to penicillins may also react to cephalosporins and other beta lactam antibiotics (BNF information on phenoxymethylpenicillin).
Cholestatic jaundice can occur with co‑amoxiclav, and is more common in people over 65 years and in men; treatment should not usually exceed 14 days (BNF information on co-amoxiclav).
Tetracyclines (for example, doxycycline) can deposit in growing bone and teeth (by binding to calcium) causing staining and occasionally dental hypoplasia. They should not be given to pregnant or breastfeeding women, and use in children under 12 years is either contraindicated or there is a caution for use only in severe or life-threatening infections when there are no alternatives (BNF information on doxycycline).
Co‑trimoxazole is associated with rare but serious side effects, including blood disorders and Stevens–Johnson syndrome. There is caution for use in older people because there is an increased risk of serious side effects. There is also caution for use in people with a predisposition to hyperkalaemia. Monitoring of blood counts is recommended with prolonged treatment (BNF information on co-trimoxazole).
See the summaries of product characteristics for information on contraindications, cautions and adverse effects of individual medicines.
Medicines adherence may be a problem for some people taking antibiotics that need frequent dosing or longer treatment duration (see the NICE guideline on medicines adherence).