15th March 2024

Penicillins

The spectrum of activity ranges from the narrow spectrum (penicillin V) to the newer semi-synthetic, extended-spectrum penicillins. β-lactamase inhibitors such as clavulanic acid and tazobactam protect the drug from being broken down, in turn, widening its coverage to β-lactamase producing bacteria. Amoxicillin and clavulanic acid combined have a wide spectrum of activity against gram negatives, positives and certain anaerobes, whereas piperacillin and tazobactam cover the same but with added antipseudomonal activity.

Adverse effects include rashes such as erythema multiforme, Steven Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). The latter two are rare, acute, and potentially fatal mucocutaneous reactions with epidermal detachment. Penicillins can lead to hypersensitivity reactions causing rash, wheezing, coughing, tightness of the chest and angioedema. There is a risk of Clostridium difficile colonisation, drug-induced liver injury and anaphylaxis, which is higher in those with a history of atopy.