foscarnet sodium hexahydrate: clinical use

Prescribing considerations

• Use under specialist hospital supervision.
• Correct dehydration and electrolyte deficiencies before treatment and maintain appropriate hydration.
• Assess whether the patient can tolerate the associated sodium and fluid load.
• Avoid rapid intravenous injection.
• Review nephrotoxic and QT-prolonging co-medication and infusion-line compatibility.
• Consider reduced viral susceptibility if the clinical response is absent or deteriorates.

Contraindications and cautions

• Hypersensitivity to foscarnet sodium hexahydrate or an excipient.
• Use particular caution with renal impairment, significant electrolyte disturbance, prolonged QT, bradycardia or structural heart disease.
• Avoid where a saline load cannot be tolerated, such as some cases of cardiomyopathy.
• Safety and efficacy have not been established in children; deposition in developing teeth, bone and cartilage is a concern from animal data.

Monitoring

• Renal function and hydration status.
• Ionised calcium where appropriate, magnesium, potassium and other relevant electrolytes.
• ECG and cardiac symptoms in patients with rhythm-risk factors or interacting medicines.
• Full blood count and relevant liver or pancreatic laboratory markers according to clinical context.
• Infusion site, genital irritation and urine-related symptoms.
• Clinical and ophthalmic response, with viral susceptibility testing considered when resistance is suspected.

Clinical pharmacology

Foscarnet directly inhibits viral DNA polymerase and reverse transcriptase without requiring intracellular phosphorylation. It undergoes no metabolic conversion, has low protein binding and is eliminated mainly through glomerular filtration.

Formulation and product differences

• Clear, colourless ready-made solution for intravenous infusion.
• May be used undiluted through a central vein; peripheral administration requires aseptic dilution with a compatible fluid.
• Contains a clinically significant sodium load.
• Contains dilute hydrochloric acid for pH adjustment and water for injections.
• Has multiple infusion incompatibilities and should not share an infusion cannula with other medicines.
• The unopened product must not be refrigerated or frozen because precipitation may occur.

Solution for infusion

Route: Intravenous

Strengths: 24 mg/mL