💊 Antifungals (Echinocandins)

Echinocandins are a class of antifungal drugs, often referred to as 'penicillin for fungi' due to their cell wall targeting mechanism. They are considered broad-spectrum antifungals, particularly effective against Candida and Aspergillus species.

Echinocandins inhibit the synthesis of β-(1,3)-D-glucan, a crucial component of the fungal cell wall. This leads to osmotic instability and lysis of the fungal cell. Their action is fungicidal against most Candida species and fungistatic against Aspergillus.

Echinocandins are primarily indicated for invasive candidiasis, including candidaemia, and oesophageal candidiasis. They are also used for empirical therapy in febrile neutropenia where fungal infection is suspected. Caspofungin is licensed for salvage therapy in invasive aspergillosis in patients refractory to or intolerant of other therapies.

Hypersensitivity to the active substance or any excipients is an absolute contraindication. Caution is advised in patients with hepatic impairment, particularly severe impairment, as dose adjustments may be necessary. There is limited experience in pregnant or breastfeeding women, so use should be avoided unless clearly necessary.

Common adverse effects include gastrointestinal disturbances (nausea, vomiting, diarrhoea), headache, and fever. Infusion-related reactions such as flushing, rash, and pruritus can occur. Liver enzyme elevations are possible, and rarely, anaphylaxis has been reported.

Liver function tests (LFTs) should be monitored, especially in patients with pre-existing hepatic impairment or during prolonged therapy. Renal function should also be assessed. Patients should be observed for infusion-related reactions during administration.

When prescribing, always check for known allergies to echinocandins or their excipients. Be mindful of potential drug interactions, although they are generally fewer than with azoles; however, co-administration with ciclosporin may increase echinocandin levels. Counsel patients on potential infusion-related reactions and to report any signs of allergic reaction.

High-yield facts include their fungicidal action against Candida and fungistatic against Aspergillus. Remember their unique cell wall target (β-(1,3)-D-glucan). They are often first-line for severe invasive candidiasis, especially in critically ill patients, due to good safety profile and broad Candida coverage. Less drug interactions compared to azoles.

SBA questions often focus on identifying the appropriate antifungal for invasive candidiasis in critically ill patients, or for empirical therapy in neutropenic fever. Another common theme is distinguishing echinocandins from azoles or polyenes based on their mechanism of action or spectrum. Questions might also test knowledge of their use in patients intolerant to other antifungals.