degarelix

Action

Binds reversibly to the pituitary GnRH receptors, thereby reducing the release of gonadotropins and consequently testosterone

Availability

Powder for injection: 80 mg/vial, 120 mg/vial

Indications and dosages

➣ Advanced prostate cancer
Adults: Initially, 240 mg subcutaneously given as two injections of 120 mg each, followed by maintenance dose of 80 mg subcutaneously as a single injection every 28 days

Contraindications

• Hypersensitivity to drug or its components

• Females of childbearing potential

Precautions

Use cautiously in:

• moderate or severe renal impairment (creatinine clearance less than 50 ml/minute)

• severe hepatic dysfunction

• congenital long QT syndrome, electrolyte abnormalities, congestive heart failure, and in patients taking Class IA (such as quinidine, procainamide) or Class III (such as amiodarone, sotalol) antiarrhythmics

• children (safety and efficacy not established).

Administration

• Be aware that drug is intended for deep subcutaneous administration only and isn't to be administered I.V.

• Wear gloves during preparation and administration.

• Reconstitute powder with sterile water for injection. Don't use other solutions.

• Be aware that the treatment initiation pack contains two vials of Firmagon 120 mg that must be prepared for two subcutaneous injections; therefore, the instructions below need to be repeated a second time.

• For initial 120-mg dose, draw up 3 ml sterile water for injection using supplied reconstitution needle (21G, 2 inches) and slowly inject sterile water for injection into 120-mg vial to yield a concentration of 40 mg/ml.

• For 80-mg maintenance dose, draw up 4.2 ml sterile water for injection using supplied reconstitution needle (21G, 2 inches) and slowly inject sterile water for injection into 80-mg vial to yield a concentration of 20 mg/ml.

• Hold vial upright and swirl it very gently until liquid is clear and without undissolved powder or particles. If powder adheres to vial over the liquid surface, vial can be tilted slightly to dissolve powder. Don't shake vial, to prevent foam formation. A ring of small air bubbles on the surface of the liquid is acceptable. The reconstitution procedure may take up to 15 minutes.

• Tilt vial slightly and keep needle in lowest part of vial. Withdraw 3 ml of drug (120-mg dose) and 4 ml (80-mg dose) without turning vial upside down.

• Exchange reconstitution needle with administration needle for deep subcutaneous injection (27G, 1¼ inches). Remove any air bubbles.

• Use reconstituted drug within 1 hour after addition of sterile water for injection.

• Give injection in abdomen in area that won't be exposed to pressure (such as not close to waistband or belt or close to ribs).

Adverse reactions

CNS: fatigue, asthenia, dizziness, headache, insomnia

CV: hypertension, prolonged QT interval

GI: nausea, constipation

GU: urinary tract infection

Hepatic: abnormal hepatic function

Musculoskeletal: decreased bone density (with long-term therapy), back pain, arthralgia

Other: injection-site reactions, hot flashes, weight gain, fever, chills, night sweats, anti-degarelix antibody development

Interactions

Drug-diagnostic tests. Gammaglutamyltransferase, serum transaminases: increased levels

Patient monitoring

• Monitor renal and hepatic function tests closely.

Monitor patient on long-term androgen deprivation therapy for prolonged QT interval.

• Monitor testosterone concentration monthly until medical castration is achieved in patients with hepatic impairment; then consider every-other-month testosterone concentration measurement.

• Because this drug may suppress pituitary gonadal system, periodically monitor drug's therapeutic effect by measuring serum concentration of prostate-specific antigen (PSA). If PSA increases, measure serum testosterone concentration.

Patient teaching

• Advise patient to make sure injection site is free of pressure from belts, waistbands, or other types of clothing.

Instruct patient to immediately report abnormal heartbeats, dizziness, or faintness.

• Tell patient that drug isn't indicated for use in women.

• Inform patient of possible adverse effects of androgen deprivation (hot flashes, skin flushing, increased weight, decreased sex drive, erectile dysfunction).

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the tests mentioned above.