phenindione: clinical use

Prescribing considerations

• Confirm and regularly review the continuing indication and bleeding risk.
• Provide a patient-held anticoagulant record and counselling about bleeding, interactions, dietary consistency and procedures.
• Use particular caution with recent ischaemic stroke, previous gastrointestinal bleeding, active peptic ulceration, older age, falls risk, anaemia, malignancy or acute illness.
• Seek specialist input for protein C or protein S deficiency because of the risk of skin necrosis.
• Review all new, stopped or changed medicines and arrange additional INR monitoring where appropriate.

Contraindications and cautions

• Hypersensitivity to phenindione or an excipient
• Haemorrhagic stroke or clinically significant bleeding
• Major surgery carrying a severe bleeding risk within the preceding 72 hours
• Within 48 hours postpartum
• Pregnancy and breastfeeding
• Severe renal or hepatic disease
• Bacterial endocarditis, actual or potential haemorrhagic conditions, or uncontrolled hypertension
• Combinations where interactions create a significantly increased bleeding risk, including fibrinolytics

Monitoring

• Monitor INR closely during initiation and continue regular testing once stable.
• Increase INR surveillance after medicine changes, acute illness, major dietary change or where adherence is uncertain.
• Investigate unexpected bleeding even when INR appears therapeutic.
• If hypersensitivity or relevant systemic adverse effects occur, assess full blood count, liver function and renal function.

Clinical pharmacology

Phenindione is a synthetic vitamin K antagonist that reduces formation of clotting factors II, VII, IX and X. Oral absorption is rapid, but the anticoagulant response develops later and can persist after treatment stops.

Formulation and product differences

• The selected product is a green, uncoated tablet with a score line that is not intended for breaking.
• It contains lactose and is unsuitable for patients with specified rare hereditary disorders of galactose or lactose handling.

Tablet

Route: Oral

Strengths: 10 mg, 25 mg