Anti-fungal drugs Flashcards
What are common indications?
- Local infections
- systemic treatment of invasive or disseminated fungal infection.
What is the mechanism of action polyene antifungals e.g nystatin?
Polyene antifungals bind to ergosterol(not found in human cells) in cell membranes creating a polar pore which allows intracellular ions to leak out of the cell.
Can kill or slow growth of fungi
What is the mechanism of action of imidazole and triazole antifungals?
Give examples of imidazole and triazole
They inhibit ergosterol synthesis, impairing cell membrane synthesis, growth and replication.
imidazole= clotrimazole
triazole=fluconazole
What is mechanism of resistance of fungal organisms?and why does it occur
Altering of membrane synthesis to exclude ergosterol, changes in target enzymes or increased efflux.
Occurs with long term use
in immune suppression
Who should be prescribed with caution/ avoided?
Topically, no major contraindications
Fluconazole should be prescribed with caution in liver disease and QT interval prolongation.
Dose reduction for moderate renal impairment
Avoided in pregnancy due to risk of fetal malformation.
What are important interactions?
No topical interactions
Fluconazole inhibits CYP450 enzymes causing increase in plasma concentration and risk of adverse effects.
May reduce platelet actions of clopidogrel
increases risk of arrhythmia if prescribed with drugs that prolong QT interval
What are important side effects?
topical administration -local irritation
Fluconazole-
GI upset (nausea, vomiting, diarrhoea, abdominal pain)
headache
increase in LFT
skin rash
RARE:
severe hepatic toxicity
prolonged QT interval predisposing to arrhythmias;
severe hypersensitivity, including cutaneous reactions and anaphylaxis.
What are dosages for fluconazole?
Fluconazole is prescribed as a single dose of 150mg orally for vaginal candidiasis.
For other mucosal infections, e.g. of the oropharynx, oesophagus, and airways, the dose is 50mg OD for a more prolonged course (e.g. 1–2weeks). T
Fluconazole used as an IV preparation for invasive or disseminated fungal infection.
What signs should patients on prolonged fluconazole be told to look out for and why?
y unusual symptoms such as nausea, loss of appetite, lethargy, or dark urine, as these could indicate liver damage.
What are monitoring requirements?
Safety should be monitored by measuring LFT before, during and after for long course of fluconazole.
What medications can cause oral fungal infections and why?
Antibiotics
systemic or inhaled corticosteroids
antimuscarinics; reduce saliva (natural defence mechanism)
A sore mouth can reduce appetite and delay recovery.
Which group of patients are susceptible to oral fungal infections?
Elderly admitted into hospital
