Oral Metastatic castration-resistant prostate cancer
Adult: In men who are asymptomatic or mildly symptomatic after failure of androgen deprivation therapy in whom chemotherapy is not yet clinically indicated or whose disease has progressed on or after docetaxel therapy: 160 mg as a single dose once daily. If greater than or equal to grade 3 toxicity or intolerable side effects occurs, withhold treatment for 1 week or until symptoms improve to less than or equal to grade 2 toxicity, then resume to normal dosing or reduce to 80-120 mg once daily if needed. Recommendations may vary among countries. Refer to specific product guidelines.
Oral Non-metastatic castration-resistant prostate cancer
Adult: 160 mg as a single dose once daily. If greater than or equal to grade 3 toxicity or intolerable side effects occurs, withhold treatment for 1 week or until symptoms improve to less than or equal to grade 2 toxicity, then resume to normal dosing or reduce to 80-120 mg once daily if needed. Recommendations may vary among countries. Refer to specific product guidelines.
Oral Hormone sensitive metastatic prostate cancer
Adult: In combination with androgen deprivation therapy: 160 mg as a single dose once daily. If greater than or equal to grade 3 toxicity or intolerable side effects occurs, withhold treatment for 1 week or until symptoms improve to less than or equal to grade 2 toxicity, then resume to normal dosing or reduce to 80-120 mg once daily if needed. Recommendations may vary among countries. Refer to specific product guidelines.
Special Patient Group
Patient taking strong CYP2C8 inhibitors: 80 mg once daily.
Patient taking strong CYP3A4 inducers: 160-240 mg once daily.
Administration
May be taken with or without food. Swallow whole, do not chew/dissolve/open cap.
Contraindications
Hypersensitivity. Females. Concomitant use with warfarin. Pregnancy and lactation.
Special Precautions
Patient with a history or risk for seizures (e.g. history of traumatic brain or head injury, CVA or TIA, arteriovenous malformation, brain infection; Alzheimer's disease, meningioma, leptomeningeal disease from prostate cancer, unexplained loss of consciousness within the last 12 months, presence of a space occupying brain lesion), history or risk of QT-interval prolongation, recent CV disease (e.g. recent MI, unstable angina, heart failure [New York Heart Association class III or IV except if LVEF ≥45%], bradycardia, uncontrolled hypertension). Severe renal and hepatic impairment.
Adverse Reactions
Significant: Falls and fractures; hypersensitivity reactions (e.g. face, tongue, lip, or pharyngeal oedema); posterior reversible encephalopathy syndrome (PRES), seizure; 2nd primary malignancies (e.g. bladder cancer, adenocarcinoma of the colon, transitional cell carcinoma, bladder transitional cell carcinoma). Blood and lymphatic system disorders: Leucopenia, neutropenia. Gastrointestinal disorders: Nausea, vomiting, diarrhoea, dysgeusia. General disorders and administration site conditions: Asthenia, fatigue. Musculoskeletal and connective tissue disorders: Arthralgia, back pain; muscle rigidity, pain, or weakness. Nervous system disorders: Headache, cognitive dysfunction, restless legs syndrome. Psychiatric disorders: Anxiety, memory impairment, insomnia. Reproductive system and breast disorders: Gynaecomastia. Skin and subcutaneous tissue disorders: Dry skin, pruritus. Vascular disorders: Hot flush, hypertension. Potentially Fatal: Ischaemic heart disease (e.g. grade 3 or 4 ischaemic events).
This drug may cause psychiatric and neurologic events, including seizures; if affected, do not drive or operate machinery.
Monitoring Parameters
Evaluate fall and fracture risk. Monitor blood pressure, CBC with differential, and LFTs at baseline and as necessary. May perform additional INR monitoring in patients taking warfarin. Assess for signs and symptoms of ischaemic heart disease, seizures, and PRES.
May decrease the serum concentration of warfarin; avoid concomitant use or conduct additional INR monitoring. Increased serum concentration with strong CYP2C8 inhibitors (e.g. gemfibrozil) and strong CYP3A4 inhibitors (e.g. itraconazole). Decreased serum concentration with strong CYP3A4 inducers (e.g. rifampicin, rifabutin, rifapentine, carbamazepine, phenytoin, phenobarbital). May decrease the serum concentration of hypnotics (e.g. midazolam, zolpidem, diazepam), opioid analgesics (e.g. fentanyl, tramadol, methadone, alfentanil), antiepileptics (e.g. clonazepam), antihypertensives (e.g. bisoprolol, diltiazem, verapamil, felodipine, nifedipine, nicardipine), corticosteroids (e.g. dexamethasone, prednisone, prednisolone), HIV antivirals (e.g. indinavir, ritonavir), antiarrhythmics (e.g. quinidine, disopyramide, amiodarone), immunosuppressants (e.g. tacrolimus, sirolimus, ciclosporin), omeprazole, atorvastatin, haloperidol, clarithromycin, and cabazitaxel.
Food Interaction
Decreased serum concentration with St John's wort.
Lab Interference
May impair the results of various assays, thereby causing falsely elevated digoxin levels or even therapeutic digoxin levels for patients not taking digoxin; consider the use of an alternative method (e.g. mass spectrometry).
Action
Description: Mechanism of Action: Enzalutamide is a pure androgen receptor signalling inhibitor. It competitively inhibits androgen binding to its receptors thus inhibiting nuclear translocation of androgen receptors and their interaction with DNA. This results in cellular apoptosis and a decreased prostate tumour volume. Pharmacokinetics: Absorption: Rapidly absorbed. Time to peak plasma concentration: 1 hour (range: 0.5-3 hours). Distribution: Volume of distribution: 110 L. Plasma protein binding: 97-98% mainly to albumin (enzalutamide); 95% (N-desmethyl enzalutamide). Metabolism: Extensively metabolised in the liver mainly by the CYP2C8 isoenzyme to the active metabolite, N-desmethyl enzalutamide and to a lesser extent by the CYP3A4 isoenzyme; undergoes further metabolism by carboxylesterase 1 to the inactive carboxylic acid metabolite. Excretion: Mainly via urine (71% as inactive metabolites); faeces (14% as inactive metabolites). Terminal elimination half-life: Enzalutamide: 6 days (range: 2.8 to 10.2 days); N-desmethyl enzalutamide: 7.8 to 8.6 days.
Chemical Structure
Enzalutamide Source: National Center for Biotechnology Information. PubChem Database. Enzalutamide, CID=15951529, https://pubchem.ncbi.nlm.nih.gov/compound/Enzalutamide (accessed on Jan. 22, 2020)
Storage
Store below 30°C. Protect from moisture. This is a cytotoxic drug. Follow applicable procedures for receiving, handling, administration, and disposal.
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