ABIRATERONE ACETATE

ABIRATERONE ACETATE

(a′-bir-a′-ter-one as′-e-tate)

Zytiga

Classifications: ANTIANDROGEN;

ANDROGEN BIOSYNTHESIS INHIBITOR

Therapeutic: ANTIANDROGEN

Pregnancy Category: X

AVAILABILITY Tablet

ACTION & THERAPEUTIC EFFECT

Inhibits the enzyme required for androgen biosynthesis in testicular, adrenal, and prostatic tumor tissues. Enzyme inhibition may also result in increased mineralocorticoid production in the adrenal glands. Decreased levels of serum testosterone and other androgens slow the growth of androgen-sensitive carcinomas.

USES Metastatic castration-resistant prostate cancer.

CONTRAINDICATIONS Severe hepatic impairment (Child-Pugh class C); pregnancy (category X).

CAUTIOUS USE History of CV

disease (e.g., heart failure, hypertension,

recent MI, ventricular

arrhythmias); hypokalemia; fluid

retention; concurrent steroid therapy,

especially during dosage adjustment

or with concurrent infection or

stress; moderate hepatic impairment

(Child-Pugh class B). Abiratrone is

not indicated for use in children.

ROUTE & DOSAGE

Metastatic Prostate Cancer

Adult: PO 1000 mg once daily in combination with PO prednisone  5 mg b.i.d. Hepatic Impairment Dosage Adjustment

Moderate impairment (Child-Pugh class B): PO 250 mg once daily

Severe impairment (Child-Pugh class C): Do not use

ADMINISTRATION

Oral

■ Give on an empty stomach 2 h before or 1 h after food.

■ Tablets should be swallowed whole with water.

■ Women who are or may be pregnant must use gloves to handle abiraterone.

■ Store at 15°–30° C (59°–86° F).

ADVERSE EFFECTS (≥1%) CV:

Arrhythmia, cardiac failure, chest pain or discomfort, hot flush, hypertension. GI: Diarrhea, dyspepsia. Metabolic: Edema, elevated ALT and AST, elevated total bilirubin, elevated triglycerides, hypokalemia, hypophosphatemia. Musculoskeletal: Joint discomfort and swelling, muscle discomfort. Respiratory: Cough, upper respiratory tract infection. Urogenital: Nocturia, urinary frequency,

urinary tract infection.

INTERACTIONS Drug: Abiraterone can increase the levels of drugs requiring CYP2D6 (e.g., dextromethorphan, thioridazine). Strong inhibitors of CYP3A4 (e.g., ketoconazole, itraconazole, clarithromycin, atazanavir, nefazodone, saquinavir, telithromycin,

ritonavir, indinavir, nelfinavir, voriconazole) increase abiraterone while inducers of CYP3A4 (e.g., phenytoin, carbamazepine,

rifampin, rifabutin, rifapentine, phenobarbital) decrease levels of abiraterone.

PHARMACOKINETICS: 2 h. Distribution: Greater than 99% Plasma protein bound. Metabolism: In the liver to an active  metabolite. Elimination: Fecal (88%) and renal (5%). Half-Life: 7–17 h.

NURSING IMPLICATIONS

Assessment & Drug Effects

■ Monitor BP and cardiac function especially with a history of CV disease. ■ Monitor for and report signs of fluid retention (e.g., sudden weight gain, peripheral edema).

■ Monitor for and report S&S of hypokalemia or hepatotoxicity (see Appendix F). Withhold drug and  notify prescriber if AST/ALT is

above 5 × ULN or bilirubin above 3 × ULN.

■ Monitor lab tests: ALT, AST, and bilirubin at baseline, then q2wk for first 3 mo, then monthly thereafter; monitor serum electrolytes (especially potassium).

Patient & Family Education

■ Do not take this drug within 2 h before or 1 h after consuming food.

■ A condom should be used during sexual intercourse with a woman who is or could become pregnant.

■ Report any of the following to a health care provider: Sudden weight gain, swelling of feet or legs, palpitations, unusual weakness,

muscle pain, S&S of a urinary tract infection.