foscarnet trisodium hexahydrate: clinical use

Prescribing considerations

• Individualise treatment according to renal function and reassess if kidney function changes.
• Correct dehydration before treatment and maintain adequate hydration.
• Consider the substantial sodium load, particularly where saline loading cannot be tolerated or a low-sodium diet is required.
• Use cautiously with renal disease, nephrotoxic therapy, electrolyte disturbance, cardiac disease, bradycardia or prolonged QT.
• Safety and efficacy have not been established in children; guidance is also not established for haemodialysis.
• Consider antiviral susceptibility testing if response is absent or deteriorates after initial improvement.

Contraindications and cautions

• Hypersensitivity to foscarnet or any product excipient.

Monitoring

• Serum creatinine, calculated renal function and urine output
• Calcium, magnesium, potassium, phosphate and other relevant electrolytes
• Hydration status and sodium burden
• ECG and cardiac status when arrhythmia risk is increased
• Full blood count and clinically indicated hepatic or pancreatic tests
• Infusion site, neurological symptoms and genital irritation or ulceration

Clinical pharmacology

Foscarnet directly inhibits viral DNA polymerases and reverse transcriptase without requiring intracellular phosphorylation. It undergoes no metabolic conversion, has low plasma-protein binding and is eliminated mainly unchanged by glomerular filtration; exposure therefore rises when renal function declines.

Formulation and product differences

• The selected product is a clear, colourless solution for intravenous infusion supplied in a single-patient glass bottle.
• It may be administered undiluted through a central vein; peripheral-vein use requires aseptic pharmacy dilution with sodium chloride or glucose solution.
• It must not be mixed with calcium-containing solutions or listed incompatible medicines, and other medicines should not be infused concurrently through the same line.
• The formulation contains water for injection and hydrochloric acid and has a clinically relevant sodium content.
• Unopened bottles should not be refrigerated or stored above the stated product limit because low temperatures can cause precipitation.

Solution for infusion

Route: Intravenous

Strengths: 24 mg/mL