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WARNINGS AND PRECAUTIONS:
>Patients should not use STENDRA if sexual activity is inadvisable due to cardiovascular status or any other reason.
>Use of STENDRA with alpha-blockers, other antihypertensives, or substantial amounts of alcohol (greater than 3 units) may lead to hypotension.
>Patients should seek emergency treatment if an erection lasts greater than 4 hours.
>Patients should stop STENDRA and seek medical care if a sudden loss of vision occurs in one or both eyes, which could be a sign of Non Arteritic Ischemic Optic Neuropathy (NAION). Discuss with patients the increased risk of NAION in patients with a history of NAION.
>Patients should stop taking STENDRA and seek prompt medical attention in the event of sudden decrease or loss of hearing.
INDICATIONS AND USAGE
>STENDRA is a phosphodiesterase 5 (PDE5) inhibitor indicated for the treatment of erectile dysfunction.
DOSAGE AND ADMINISTRATION
For most patients, the starting dose is 100 mg taken approximately 30 minutes before sexual activity, on an as needed basis. Take STENDRA no more than once a day.
The dose may be increased to 200 mg or decreased to 50 mg based on efficacy and/or tolerability. Use the lowest dose that provides benefit.
STENDRA may be taken with or without food.
Do not use STENDRA with strong CYP3A4 inhibitors.
If taking a moderate CYP3A4 inhibitor, the dose should be no more than 50 mg in a 24-hour period.
In patients on stable alpha-blocker therapy, the recommended starting dose of STENDRA is 50 mg.
DOSAGE FORMS AND STRENGTHS
Tablets: 50 mg, 100 mg, 200 mg
Sildenafil (Viagra ®)
Phosphodiesterase-5 Enzyme Inhibitor.
Mechanism of Action
The physiologic mechanism of erection of the penis involves release of nitric oxide (NO) in the corpus cavernosum during sexual stimulation. NO then activates the enzyme guanylate cyclase, which results in increased levels of cyclic guanosine monophosphate (cGMP), producing smooth muscle relaxation in the corpus cavernosum and allowing inflow of blood. Sildenafil has no direct relaxant effect on isolated human corpus cavernosum, but enhances the effect of nitric oxide (NO) by inhibiting phosphodiesterase type 5 (PDE5), which is responsible for degradation of cGMP in the corpus cavernosum. When sexual stimulation causes local release of NO, inhibition of PDE5 by sildenafil causes increased levels of cGMP in the corpus cavernosum, resulting in smooth muscle relaxation and inflow of blood to the corpus cavernosum. Sildenafil at recommended doses has no effect in the absence of sexual stimulation.
Studies in vitro have shown that sildenafil is selective for PDE5. Its effect is more potent on PDE5 than on other known phosphodiesterases (10-fold for PDE6, >80-fold for PDE1, >700-fold for PDE2, PDE3, PDE4, PDE7, PDE8, PDE9, PDE10, and PDE11). The approximately 4,000-fold selectivity for PDE5 versus PDE3 is important because PDE3 is involved in control of cardiac contractility. Sildenafil is only about 10-fold as potent for PDE5 compared to PDE6, an enzyme found in the retina which is involved in the phototransduction pathway of the retina. This lower selectivity is thought to be the basis for abnormalities related to color vision observed with higher doses or plasma levels.
In addition to human corpus cavernosum smooth muscle, PDE5 is also found in lower concentrations in other tissues including platelets, vascular and visceral smooth muscle, and skeletal muscle. The inhibition of PDE5 in these tissues by sildenafil may be the basis for the enhanced platelet antiaggregatory activity of nitric oxide observed in vitro, an inhibition of platelet thrombus formation in vivo and peripheral arterial-venous dilatation in vivo.
Dosing (Adults): Oral:
Erectile dysfunction: For most patients, the recommended dose is 50 mg taken as needed, approximately 1 hour before sexual activity. However, sildenafil may be taken anywhere from 30 minutes to 4 hours before sexual activity. Based on effectiveness and tolerance, the dose may be increased to a maximum recommended dose of 100 mg or decreased to 25 mg. The maximum recommended dosing frequency is once daily.
Primary pulmonary hypertension (unlabeled use): 25 mg twice daily, titrated based on response. Dosages up to 100 mg 5 times/day have been used (limited data).
Dosage adjustment for patients >65 years of age, hepatic impairment (cirrhosis), severe renal impairment (creatinine clearance <30 mL/minute), or concomitant use of potent cytochrome P450 3A4 inhibitors (erythromycin, ketoconazole, itraconazole, ritonavir, amprenavir): Higher plasma levels have been associated which may result in increase in efficacy and adverse effects and a starting dose of 25 mg should be considered
Supplied: Viagra®: 25 mg, 50 mg, 100 mg tablet.
tadalafil (Cialis ®)
PDE-5 enzyme inhibitor.
Dosing (Adults): Erectile dysfunction: 10 mg orally prior to anticipated sexual activity (dosing range: 5-20 mg) - to be given as a single dose and not given more than once daily (Erectile function may be improved for up to 36 hours following a single dose).
Drug interactions: Alpha blockers: If stabilized on either alpha blockers or tadalafil therapy, initiate new therapy with the other agent at the lowest possible dose. CYP3A4 inhibitors: Dose reduction of tadalafil is recommended with strong CYP3A4 inhibitors. The dose of tadalafil should not exceed 10 mg, and tadalafil should not be taken more frequently than once every 72 hours. Some examples include: (azole antifungals, clarithromycin, doxycycline, erythromycin, grapefruit juice, imatinib, isoniazid, nefazodone, protease inhibitors, others...)
Crcl 31-50 ml/min: Initial dose 5 mg once daily - maximum dose 10 mg not to be given more frequently than every 48 hours.
Crcl <30 ml/min or hemodialysis: Maximum dose 5 mg.
Mild-to-moderate hepatic impairment (Child-Pugh class A or B): Do not exceed 10 mg once daily.
Severe hepatic impairment: Use is not recommended.
Supplied: 5 mg, 10 mg, 20 mg tablet.
vardenafil (Levitra ®)
PDE-5 enzyme inhibitor.
Dosing (Adults): Erectile dysfunction: 10 mg orally 1 hour prior to sexual activity. Dosing range: 5-20 mg (given as one single dose and not given more than once daily). Patients >/= 65 yrs old: Initial: 5 mg 1 hr prior to sexual activity- to be given as one single dose and not given more than once daily.
Drug interactions: Alpha blocker (dose should be stable at time of vardenafil initiation): Initial vardenafil dose: 5 mg/24 hrs. If an alpha blocker is added to vardenafil therapy, it should be initiated at the smallest possible dose, and titrated carefully. Other: Erythromycin: Max vardenafil dose: 5 mg/24 hrs. Indinavir: Max dose: 2.5 mg/24 hrs. Itraconazole: 200 mg/day: Max dose: 5 mg/24 hours. 400 mg/day: Max dose: 2.5 mg/24 hrs. Ketoconazole: 200 mg/day: Max dose: 5 mg/24 hrs. 400 mg/day: Max dose: 2.5 mg/24 hrs. Ritonavir: Max dose: 2.5 mg/72 hrs.
Hepatic impairment: Child-Pugh class B: Initial: 5 mg 1 hr prior to sexual activity (max dose: 10 mg)- to be given as one single dose and not given more than once daily.
Supplied:: 2.5 mg, 5 mg, 10 mg, 20 mg tablet.
National Institutes of Health, U.S. National Library of Medicine,
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Listed dosages are for - Adult patients ONLY. PLEASE READ THE
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TO BE BOUND BY THE TERMS AND CONDITIONS SET FORTH IN THE DISCLAIMER.
GlobalRPH does not directly or indirectly practice medicine or provide
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David F. McAuley, Pharm.D., R.Ph. GlobalRPh Inc.