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.
Cholestatic jaundice and hepatitis can occur with flucloxacillin up to 2 months after stopping treatment, with risk factors being increasing age and use for more than 14 days (flucloxacillin, BNF, January 2020). Cholestatic jaundice can also occur with co-amoxiclav, and is more common in people over 65 years and in men; treatment should not usually exceed 14 days (co-amoxiclav, BNF, January 2020).
People with a history of immediate hypersensitivity to penicillin may also react to cephalosporins and other beta-lactam antibiotics (phenoxymethylpenicillin, BNF, January 2020).
Macrolides (for example, clarithromycin) should be used with caution in people with a predisposition to QT interval prolongation. Nausea, vomiting, abdominal discomfort, and diarrhoea are the most common side effects of macrolides. These are less frequent with clarithromycin than with erythromycin (erythromycin, BNF, January 2020).
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 women or women who are breastfeeding, and use in children under 12 years is either contraindicated or cautioned for use in severe or life-threatening infections where there are no alternatives. People should be advised to avoid exposure to sunlight or sun lamps because of photosensitivity reactions (doxycycline, BNF, January 2020).
Co-trimoxazole is associated with rare but serious side effects, including blood disorders and Stevens−Johnson syndrome. It is cautioned for use in older people because there is an increased risk of serious side effects, and in those with a predisposition to hyperkalaemia. Monitoring of blood counts is recommended with prolonged treatment (co-trimoxazole, BNF, January 2020).
Aminoglycoside (for example, gentamicin) doses are based on body weight and renal function. Ototoxicity and nephrotoxicity are important side effects to consider, and whenever possible treatment should not exceed 7 days (gentamicin, BNF, January 2020).
Glycopeptide (for example, vancomycin and teicoplanin) doses are based on body weight. Therapeutic drug monitoring and monitoring of various patient parameters, including blood count, urinalysis, auditory function, hepatic function and renal function, is recommended, depending on the particular glycopeptide (vancomycin, BNF, January 2020).
Severe optic neuropathy can occur with linezolid, particularly if used for longer than 28 days. Blood disorders have also been reported, and weekly full blood counts are recommended (linezolid, BNF, January 2020).
See the electronic medicines compendium's 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 clinical guideline on medicines adherence).