SILDENAFIL CITRATE

SILDENAFIL CITRATE
(sil-den'a-fil ci'trate)
Revatio, Viagra
Classifications: impotence agent; phosphodiesterase (pde) inhibitor;
Therapeutic: impotence

Pregnancy Category: B

Availability

20 mg, 25 mg, 50 mg, 100 mg tablets

Action

Enhances vasodilation effect of nitric oxide in the corpus cavernosus of the penis, thus sustaining an erection.

Therapeutic Effect

Oral treatment for erectile dysfunction, whether organic or psychogenic in origin.

Uses

Erectile dysfunction, pulmonary arterial hypertension.

Contraindications

Hypersensitivity to sildenafil; concurrent administration of organic nitrates and nitroglycerin; lactation, children, infants.

Cautious Use

CAD, heart failure, MI, cardiac arrhythmias, stroke within 6 mo of starting drug; nitrate therapy; hypotension and hypertension; risk factors for CVA; aortic stenosis; anatomic deformity of the penis; sickle cell anemia, polycythemia; multiple myeloma; leukemia; active bleeding or a peptic ulcer, GERD, hiatal hernia; coagulopathy; retinitis pigmentosa; hepatic disease, hepatitis, cirrhosis; severe renal impairment (Clcr <30 mL/min); older adults; concurrent use with other medicines for penile dysfunction; pregnancy (category B).

Route & Dosage

Erectile Dysfunction
Adult: PO 50 mg 0.5–4 h before sexual activity (dose range: 25 to 100 mg once/d); max dose: 25 mg/d with itraconazole or ketoconazole; max dose: 25 mg/48 h with ritonavir
Geriatric: PO 25 mg approximately 1 h before sexual activity

Pulmonary Arterial Hypertension
Adult: PO 20 mg t.i.d. (4–6 h apart)

Hepatic or Severe Renal Impairment
Adult: PO 25 mg approximately 1 h before sexual activity

Administration

Oral
  • For erectile dysfunction: Dose 1 h prior to sexual activity (effective range is 0.5–4 h).
  • Do not give within 24 h of taking any medication with nitrates (i.e., nitroglycerin).
  • Store at 15°–30° C (59°–86° F) in a tightly closed container; protect from light.

Adverse Effects (≥1%)

Body as a Whole: Face edema, photosensitivity, shock, asthenia, pain, chills, fall, allergic reaction, arthritis, myalgia. CNS: Headache, dizziness, migraine, syncope, cerebral thrombosis, ataxia, neuralgia, paresthesias, tremor, vertigo, depression, insomnia, somnolence, abnormal dreams. CV: Flushing, chest pain, MI, angina, AV block, tachycardia, palpitation, hypotension, postural hypotension, cardiac arrest, sudden cardiac death, heart failure, cardiomyopathy, abnormal ECG, edema. GI: Dyspepsia, diarrhea, abdominal pain, vomiting, colitis, dysphagia, gastritis, gastroenteritis, esophagitis, stomatitis, dry mouth, abnormal liver function tests, thirst. Respiratory: Nasal congestion, asthma, dyspnea, laryngitis, pharyngitis, sinusitis, bronchitis, cough. Skin: Rash, urticaria, pruritus, sweating, exfoliative dermatitis. Urogenital: UTI. Special Senses: Abnormal vision (color changes, photosensitivity, blurred vision, sudden vision loss). Hematologic: Anemia, leukopenia. Metabolic: Gout, hyperglycemia, hyperuricemia, hypoglycemia, hypernatremia.

Interactions

Drug: nitrates increase risk of serious hypotension; if used within 4 h of doxazosin, prazosin, terazosin, tamsulosin; cimetidine, erythromycin, ketoconazole, itraconazole, protease inhibitors increase sildenafil levels; rifampin can decrease sildenafil levels. Food: Grapefruit juice (>1 qt/d) may increase plasma concentrations and adverse effects.

Pharmacokinetics

Absorption: Rapidly from GI tract. Peak: 30–120 min. Distribution: 96% protein bound. Metabolism: In liver (CYP3A4 and 2C9). Elimination: 80% in feces, 12% in urine. Half-Life: 4 h.

Nursing Implications

Assessment & Drug Effects

  • Monitor carefully for and immediately report S&S of cardiac distress.

Patient & Family Education

  • Do not take sildenafil within 4 h of taking doxazosin, prazosin, terazosin, or tamsulosin.
  • Consuming a high-fat meal before taking drug may cause delay in drug action.
  • Report to physician: Headaches, flushing, chest pain, indigestion, blurred vision, sensitivity to light, changes in color vision.

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

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