gefitinib: prescribing and clinical use
Focused clinical detail for use alongside current product information, local policy and patient-specific assessment.
gefitinib: clinical details
Prescribing considerations
- Treatment should be initiated and supervised by a clinician experienced in anti-cancer therapy.
- Confirm an activating EGFR mutation using a robust validated tumour-tissue test; validated plasma ctDNA testing may be used when tumour material is not evaluable.
- Review pulmonary history, liver function, gastrointestinal-perforation risk, eye disease, concomitant medicines and hereditary lactose-intolerance disorders.
- Evidence is limited in severe renal impairment. Cirrhosis can substantially increase exposure.
Contraindications and cautions
- Hypersensitivity to gefitinib or any excipient.
- Breastfeeding.
- The selected lactose-containing product should not be used in galactose intolerance, total lactase deficiency or glucose-galactose malabsorption.
Monitoring
- Assess new respiratory symptoms promptly and interrupt treatment while suspected interstitial lung disease is investigated.
- Perform periodic liver-function tests; consider discontinuation for severe abnormalities.
- Monitor hydration and the severity of gastrointestinal and skin toxicity.
- Arrange prompt ophthalmology assessment for acute or worsening keratitis symptoms.
- Monitor PT or INR regularly with warfarin.
- Assess response and emerging resistance according to the specialist cancer plan.
Clinical pharmacology
Gefitinib selectively inhibits EGFR tyrosine kinase. It is metabolised mainly through CYP3A4 and CYP2D6, distributes extensively into tissues and is eliminated predominantly as metabolites in faeces.
Formulation and product differences
- The selected film-coated tablet contains lactose and is essentially sodium-free.
- It may be swallowed whole or dispersed in still water without crushing.
- Store in the original container to protect it from moisture; no special temperature conditions are required.
gefitinib preparations and strengths
Tablet
Route: Oral
Strengths: 250 mg
gefitinib interactions
The cancer team should review prescribed, over-the-counter and herbal products before treatment and whenever medicines change.
Phenytoin, carbamazepine, rifampicin, barbiturates and St John's wort
These CYP3A4 inducers can lower gefitinib exposure and may reduce its effect, so concurrent use should be avoided.
Potent CYP3A4 inhibitors, including itraconazole, ketoconazole, posaconazole, voriconazole, clarithromycin and some protease inhibitors
These can increase gefitinib exposure and adverse effects, requiring close clinical monitoring.
Proton-pump inhibitors, H2-receptor antagonists and regularly used antacids
Sustained reduction of stomach acidity can reduce gefitinib absorption and potentially its effectiveness.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.