TADALAFIL

TADALAFIL (ta-dal'a-fil) Cialis Classifications: impotence agent; phosphodiesterase (pde) inhibitor; vasodilator; Therapeutic:impotence; pde inhibitor Prototype: Sildenafil Pregnancy Category: B

Availability

5 mg, 10 mg, 20 mg tablets

Action

Tadalafil is a selective phosphodiesterase (PDE) type 5 inhibitor. PDE type 5 is responsible for degradation of cyclic GMP in the corpus cavernosum of the penis. Cyclic GMP causes smooth muscle relaxation in the corpus cavernosum, thereby allowing inflow of blood into the penis.

Therapeutic Effect

Tadalafil promotes sustained erection only in the presence of sexual stimulation.

Uses

Treatment of erectile dysfunction.

Contraindications

Hypersensitivity to tadalafil, vardenafil, or sildenafil; concurrent administration of nitrates, nitroglycerin, or any alpha-adrenergic antagonist (other than 0.4 mg q.d. tamsulosin); MI within last 90 d; Class 2 or greater heart failure within last 6 mo; unstable angina or angina during intercourse; uncontrolled cardiac arrhythmias; nitrate/nitrite therapy; hypotension, uncontrolled hypertension; retinitis pigmentosa; CVa within last 6 mo; left ventricular outflow obstruction, aortic stenosis; not recommended for women; lactation.

Cautious Use

CAD, risk factors for CVA; renal insufficiency; hepatic impairment, hepatic disease; anatomic deformity of the penis; sickle cell anemia; multiple myeloma; leukemia; active bleeding or a peptic ulcer; hiatal hernia, GERD; sickle cell disease; retinitis pigmentosa; hepatitis, cirrhosis; severe renal impairment; older adults; concurrent use with other medicines for penile dysfunction; pregnancy (category B).

Route & Dosage

Erectile Dysfunction Adult: PO 10 mg prior to anticipated sexual activity. May increase to max dose 20 mg/d or reduce to 5 mg/d if needed. If taking ritonavir, itraconazole, ketoconazole, or voriconazole, max dose 10 mg q72h. Hepatic Impairment Mild to moderate impairment: max 10 mg/d; not recommended with severe hepatic impairment Renal Impairment Clcr 30–50 mL/min: start at 5 mg once daily (max: 10 mg q48h); <30 mL/min: max dose 5 mg

Administration

Oral

• Take approximately 1 h before expected intercourse, but preferably not after a heavy or high-fat meal.
• Store at 15°–30° C (59°–86° F).

Adverse Effects (≥1%)

Body as a Whole: Flushing, back pain, asthenia, facial edema, fatigue, pain. CNS: Headache, dizziness, insomnia, somnolence, vertigo, hypesthesia, paresthesia. CV: Angina, chest pain, hypertension, hypotension, MI, orthostatic hypotension, palpitations, syncope, sinus tachycardia. GI: Dyspepsia, nausea, vomiting, abdominal pain, abnormal liver function tests, diarrhea, loose stools, dysphagia, esophagitis, gastritis, GERD, xerostomia. Metabolic: Increased GGTP. Musculoskeletal: Arthralgia, myalgia, neck pain. Respiratory: Nasal congestion, dyspnea, epistaxis, pharyngitis. Skin: Rash, pruritus, sweating. Special Senses: Blurred vision, changes in color vision, conjunctivitis, eye pain, lacrimation, swelling of eyelids, sudden vision loss. Urogenital: Spontaneous penile erection.

Interactions

Drug: May potentiate hypotensive effects of ETHANOL, NITRATES, alfuzosin, doxazosin, prazosin, tamsulosin (doses >0.4 mg/d), terazosin; erythromycin (and other MACROLIDES), indinavir, intraconazole, ketoconazole, PROTEASE INHIBITORS, ritonavir, saquinavir, voriconazole may increase levels and toxicity of tadalafil; barbiturates, bosentan, carbamazepine, dexamethasone, fosphenytoin, nevirapine, rifampin phenytoin, rifabutin, troglitazone may reduce level and effectiveness of tadalafil. Food: Grapefruit juice may increase levels and toxicity of tadalafil.

Pharmacokinetics

Absorption: Rapidly absorbed, 15% reaches systemic circulation. Onset: 30–45 min. Peak: 2 h. Duration: Up to 36 h. Metabolism: In liver by CYP3A4. Elimination: In feces (61%) and urine (39%). Half-Life: 17.5 h.

Nursing Implications

Assessment & Drug Effects

• Monitor CV status and report angina or other S&S of cardiac dysfunction.
• Lab tests: Baseline and periodic LFTs.

Patient & Family Education

• Do not take more than once per day.
• Note: With moderate renal insufficiency, the maximum recommended dose is 10 mg not more than once in every 48 h.
• Moderate use of alcohol when taking this drug.
• Do not take this drug without consulting physician if you are taking drugs called "alpha blockers" or "nitrates" or any other drugs for high blood pressure, chest pain, or enlarged prostate.
• Report promptly any of the following: palpitations, chest pain, back pain, difficulty breathing, or shortness of breath; dizziness or fainting; changes in vision; swollen eyelids; muscle aches; painful or prolonged erection (lasting longer than 4 h); skin rash, or itching.

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