Penicillins Flashcards
Give some examples of beta-lactamase sensitive penicillins.
Benzylpenicillin (penicillin G), phenoxymethylpenicillin (penicillin V).
Give some examples of broad spectrum penicillins inactivated by beta-lactamase.
Amoxicillin, ampicillin.
Give some examples of penicillinase-resistant penicillins.
Flucloxacillin.
What is the mechanism of action of the penicillins?
Inhibit cell wall synthesis by inhibiting peptidoglycan cross linking.
Describe the distribution of the penicillins.
They diffuse well into the body tissues and fluids with poor cerebrospinal fluid penetration unless the meninges are inflamed.
Against which organisms are the penicillins effective?
Gram-positive organisms and some gram-negative cocci.
What indications are the penicillins used to treat?
Oral infections, otitis media, cellulitis, RTIs, pneumonia.
What are the side effects of the penicillins?
Hypersensitivity, anaphylaxis, diarrhoea, antibiotic associated colitis, CNS toxicity (encephalopathy), hepatic disorders (flucloxacillin).
What percentage of individual exposed to penicillins will experience hypersensitivity?
1-10%.
Give the symptoms of the hepatic disorders rarely seen with flucloxacillin.
Nausea, vomiting, abdominal pain, pale stools, dark urine, pruritis.
Macropapular rashes are sometimes seen with ampicillin and amoxicillin use, this is unlikely to be a penicillin allergy. What symptoms should one look out for?
Minor, non-confluent rash which is non-pruritic and localised. Experienced over 72 hours after the dose.
Will patients allergic to one penicillin be allergic to all penicillins?
Yes, as well as the cephalosporins and other beta-lactam antibiotics.
What is the cause of bacterial resistance to the penicillins?
Beta-lactamase, an enzyme which targets the beta-lactam ring.
What other conditions may predispose someone to be at greater risk of penicillin allergy?
Atopic conditions such as eczema.
