ALPROSTADIL (PGE₁)
(al-pross'ta-dil)
Prostin VR Pediatric, Caverject, Muse, Edex
Classifications: prostaglandin
Prototype: Dinoprostone
Pregnancy Category: C

Availability

500 mcg/mL injection; 5 mcg/mL, 10 mcg/mL, 20 mcg/mL, 40 mcg/mL powder for injection; 125 mcg, 250 mcg, 500 mcg, 1000 mcg pellets

Actions

Actions include vasodilation, inhibition of platelet aggregation, and stimulation of intestinal and uterine smooth muscles.

Therapeutic Effects

Preserves ductal patency by relaxing smooth muscle of ductus arteriosus. Alprostadil induces penile erection by relaxing the smooth muscles of the corpus cavernosum and dilating the cavernosal arteries and their penile arterioles. Sufficient rigidity of the penis also requires increased venous outflow resistance, thus resulting in penile blood engorgement and erection.

Uses

Temporary measure to maintain patency of ductus arteriosus in infants with ductal-dependent congenital heart defects until corrective surgery can be performed. Also used in erectile dysfunction.

Contraindications

Ductus arteriosus respiratory distress syndrome (hyaline membrane disease); hypersensitivity to alprostadil; patients with penile implants. Muse, Edex: Women, children, and newborns; lactation. Muse: Patients with urethral stricture, inflammation/infection of glans of penis, severe hypospadias, acute or chronic urethritis; sickle cell anemia or trait, thrombocytopenia, polycythemia, multiple myeloma.

Cautious Use

Ductus arteriosus; bleeding tendencies; erectile dysfunction; hypersensitivity to alprostadil; sickle cell anemia or trait; multiple myeloma or leukemia; penile anatomic deformations; patients on anticoagulants, vasoactive or antihypertensive drugs.

Route & Dosage

To Maintain Patency of Ductus Arteriosus
Neonate: IV/Intraarterial/Intraaortic 0.05–0.1 mcg/kg/min, may increase gradually (max: 0.4 mcg/kg/min if necessary)

Erectile Dysfunction of Vasculogenic, Psychogenic, or Mixed Etiology
Adult: Intracavernosal initiate with 2.5 mcg; if inadequate response, increase dose by 2.5 mcg. May then increase dose in 5- to 10-mcg increments until a suitable erection occurs, not exceeding 1 h in duration. Doses >60 mcg not recommended

Erectile Dysfunction of Pure Neurogenic Etiology
Adult: Intracavernosal initiate with 1.25 mcg; if inadequate response, increase dose by 1.25 mcg, then increase by 2.5 mcg, may then increase dose in 5 mcg increments until a suitable erection occurs, not exceeding 1 h in duration. Doses >60 mcg not recommended

Administration

Intracavernosal Injection

Administer only after proper training in the penile injection technique. Refer to information on administration provided to the patient by the manufacturer.
Use reconstituted solutions immediately.
Store dry powder at or below 25° C (77° F) for up to 3 mo. Do not freeze.

Transurethral Insertion

Refer to information on insertion into the urethra provided to the patient by the manufacturer.

Intravenous

PREPARE: Continuous: • Dilute 500 mcg alprostadil with NS or D5W to volume appropriate for pump delivery system.• Prepare fresh solution q24h. Discard unused portions.• A 500 mcg ampule diluted in 250 mL yields a concentration of 2 mcg/mL.

ADMINISTER: Continuous: Infuse at rate of 0.05–0.1 mcg/kg/min up to a maximum of 0.4 mcg/kg/min. • Reduce infusion rate immediately if arterial pressure drops significantly or if fever occurs.• Discontinue promptly, if apnea or bradycardia occurs.

Store at 2°–8° C (36°–46° F) unless otherwise directed by manufacturer. Protect from freezing.

Adverse Effects (1%)

CNS: Fever, seizures, lethargy. CV: Flushing, bradycardia, hypotension, syncope, tachycardia; CHF, ventricular fibrillation, shock. GI: Diarrhea, gastric regurgitation. Hematologic: Disseminated intravascular coagulation (DIC), thrombocytopenia. Respiratory: Apnea. Urogenital: Oliguria, anuria. Penile pain, prolonged erection, priapism, penile fibrosis, injection site hematoma/ecchymosis, penile rash and edema, prostatitis, perineal pain. Skin: Rash on face and arms, alopecia. Other: Leg pain.

Interactions

Drug: May increase anticoagulant properties of warfarin; antihypertensive agents increase risk of hypotension.

Pharmacokinetics

Onset: 15 min to 3 h. Metabolism: Rapidly metabolized in lungs. Elimination: Metabolites excreted through kidneys. Half-Life: 5–10 min.

Nursing Implications

Assessment & Drug Effects

Ductus Arteriosus

Monitor therapeutic effectiveness which is indicated by increase in blood oxygenation (Po₂), usually evident within 30 min, in infants with cyanotic heart disease (restricted pulmonary blood flow). Normal Po₂ for neonates is 60–70 mm Hg. Indicated by increased pH in those with acidosis, increased systemic BP and urinary output, return of palpable pulses, and decreased ratio of pulmonary artery to aortic pressure in infants with restricted systemic blood flow.
Monitor for arterial pressure, ECG, heart rate, BP, respiratory rate, and rectal temperature, intermittently throughout the infusion.
Lab tests: Monitor arterial blood gases and arterial blood pH intermittently throughout the infusion.
Monitor: Systemic BP, pulmonary artery and descending aorta pressures, femoral pulse, and urinary output.

Patient & Family Education

Erectile Dysfunction

Follow carefully directions for penile injection provided by the manufacturer.
Do not change dose without consulting the physician.
Do not use intracavernosal injection more often than 3 times/wk; allow at least 24 h between uses.
Do not use more than 2 urethral suppository systems in a 24 h period.
Report nodules or hard tissue in penis; penile pain, redness, swelling, tenderness; or curvature of the erect penis to the physician as soon as possible.
Seek immediate medical attention if an erection persists longer than 6 h.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug