BNF for Children 2011-2012

BNFC 2011–2012 5.1.1 Penicillins 257Joint prostheses and dental treatmentJoint prostheses and dental treatmentAdvice of a Working Party of the British Society forAntimicrobial Chemotherapy is that patients withprosthetic joint implants (including total hip replacements)do not require antibacterial prophylaxis fordental treatment. The Working Party considers thatit is unacceptable to expose patients to the adverseeffects of antibacterials when there is no evidencethat such prophylaxis is of any benefit, but that thosewho develop any intercurrent infection requireprompt treatment with antibacterials to which theinfecting organisms are sensitive.The Working Party has commented that joint infectionshave rarely been shown to follow dental proceduresand are even more rarely caused by oralstreptococci.Immunosuppression and indwellingintraperitoneal cathetersImmunosuppression and indwelling intraperitonealcathetersAdvice of a Working Party of the British Society forAntimicrobial Chemotherapy is that patients whoare immunosuppressed (including transplantpatients) and patients with indwelling intraperitonealcatheters do not require antibacterial prophylaxis fordental treatment provided there is no other indicationfor prophylaxis.The Working Party has commented that there is littleevidence that dental treatment is followed by infectionin immunosuppressed and immunodeficientpatients nor is there evidence that dental treatmentis followed by infection in patients with indwellingintraperitoneal catheters.Hypersensitivity reactions The most importantside-effect of the penicillins is hypersensitivity whichcauses rashes and anaphylaxis and can be fatal. Allergicreactions to penicillins occur in 1–10% of exposedindividuals; anaphylactic reactions occur in fewer than0.05% of treated patients. Individuals with a history ofanaphylaxis, urticaria, or rash immediately after penicillinadministration are at risk of immediate hypersensitivityto a penicillin; these individuals should not receivea penicillin. Children who are allergic to one penicillinwill be allergic to all because the hypersensitivity isrelated to the basic penicillin structure. As patientswith a history of immediate hypersensitivity to penicillinsmay also react to the cephalosporins and other betalactamantibiotics, they should not receive these antibiotics;aztreonam may be less likely to cause hypersensitivityin penicillin-sensitive patients and can beused with caution. If a penicillin (or another beta-lactamantibiotic) is essential in a child with immediate hypersensitivityto penicillin then specialist advice should besought on hypersensitivity testing or using a beta-lactamantibiotic with a different structure to the penicillinthat caused the hypersensitivity (see also p. 266).Individuals with a history of a minor rash (i.e. nonconfluent,non-pruritic rash restricted to a small areaof the body) or a rash that occurs more than 72 hoursafter penicillin administration are probably not allergicto penicillin and in these individuals a penicillin shouldnot be withheld unnecessarily for serious infections; thepossibility of an allergic reaction should, however, beborne in mind. Other beta-lactam antibiotics (includingcephalosporins) can be used in these patients.Other side effects A rare but serious toxic effect ofthe penicillins is encephalopathy due to cerebral irritation.This may result from excessively high doses or inpatients with severe renal failure. The penicillins shouldnot be given by intrathecal injection because they cancause encephalopathy which may be fatal.Another problem relating to high doses of penicillin, ornormal doses given to patients with renal failure, is theaccumulation of electrolyte since most injectable penicillinscontain either sodium or potassium.Diarrhoea frequently occurs during oral penicillin therapy.It is most common with broad-spectrum penicillins,which can also cause antibiotic-associated colitis.5 Infections5.1.1 Penicillins5.1.1.1 Benzylpenicillin andphenoxymethylpenicillin5.1.1.2 Penicillinase-resistant penicillins5.1.1.3 Broad-spectrum penicillins5.1.1.4 Antipseudomonal penicillins5.1.1.5 MecillinamsThe penicillins are bactericidal and act by interferingwith bacterial cell wall synthesis. They diffuse well intobody tissues and fluids, but penetration into the cerebrospinalfluid is poor except when the meninges areinflamed. They are excreted in the urine in therapeuticconcentrations.5.1.1.1 Benzylpenicillin andphenoxymethylpenicillinBenzylpenicillin (Penicillin G) remains an importantand useful antibiotic but is inactivated by bacterialbeta-lactamases. It is effective for many streptococcal(including pneumococcal), gonococcal, and meningococcalinfections and also for anthrax (section 5.1.12),diphtheria, gas-gangrene, leptospirosis, and treatment ofLyme disease (section 5.1.1.3) in children. It is also usedin combination with gentamicin for the empirical treatmentof sepsis in neonates less than 48 hours old.Pneumococci, meningococci, and gonococci whichhave decreased sensitivity to penicillin have been isolated;benzylpenicillin is no longer the drug of firstchoice for pneumococcal meningitis. Althoughbenzylpenicillin is effective in the treatment of tetanus,metronidazole (section 5.1.11) is preferred. Benzylpenicillinis inactivated by gastric acid and absorption fromthe gastro-intestinal tract is low; therefore it must begiven by injection.Benzathine benzylpenicillin or procaine benzylpenicillinis used in the treatment of syphilis (see Table 1section 5.1); both are available from ‘special-order’manufacturers or specialist importing companies, seep. 809.