Table 2.
Comparison of PDE5 inhibitors
| CHARACTERISTIC | SILDENAFIL (VIAGRA) | TADALAFIL (CIALIS) | VARDENAFIL (LEVITRA) |
|---|---|---|---|
| Onset | ≤ 30–60 min | ≥ 30–60 min | ≤ 30–60 min |
| Peak effect | 1 h | 2 h | 1 h |
| Duration | > 4 h | 36 h | > 4 h |
| Available doses | 25, 50, 100 mg | 2.5, 5, 10, 20 mg | 5, 10, 20 mg |
| Usual starting dose | 50 mg | 10 mg (see Comments regarding daily dosing) | 10 mg |
| Maximum dose | 100 mg | 20 mg | 20 mg |
| Cost per 8 doses (usual dose) | $105 | $125 | $110 |
| Effect of fatty meal | Delay onset by 60 min; might decrease effect | Meal has no effect | Delay onset by 60 min; might decrease effect |
| Unique consideration | “Blue vision” effect more common | Very long acting | QT interval drug interactions (eg, TCAs) |
| Monitor (baseline) | Liver, renal | Liver, renal | Liver |
| Contraindications5 | History of MI in past 90 d or stroke in past 6 mo; angina: unstable or occurring with sexual activity; nitrate use; hypotension (BP < 90/50 mm Hg) or uncontrolled hypertension (BP > 170/100 mm Hg); priapism, retinitis pigmentosa; history of NAION; previous PDE5 inhibitor allergy | ||
| Common side effects | Headache, flushing (approximately 10%); dyspepsia, dizziness, rhinitis, altered, hazy, or blurred vision (< 10%); myalgia (possibly more with tadalafil) | ||
| Serious side effects | Rare: prolonged erection (< 4 h), priapism Very rare or uncertain: NAION, MI, hearing loss18 |
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| Drug interactions (common and important; not exhaustive) | Drugs that cause hypotension (α1 blockers, 19 nitrates, vasodilators): increased hypotensive effect, heart rate, and MI risk Nitrate washout time required: 24 h for sildenafil and vardenafil; 48 h for tadalafil CYP 3A4 inhibitors (eg, azole antifungals, erythromycin, grapefruit juice, protease inhibitors, verapamil): increased levels of the PDE5 |
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| Comments | PDE5 inhibitors might be effective in several ED-associated conditions such as diabetes,20 spinal cord injury,21 and follow-up to treatment for prostate cancer22 Moderate to high doses are useful to ensure initial treatment success; however, consider lower dose if the patient is elderly, has hepatic or renal dysfunction (vardenafil does not require dose adjustment for renal function), or is taking concomitant CYP 3A4 inhibitors Because of tadalafil’s long action, daily dosing of 2.5–5 mg (or 5–10 mg 3 times/wk) might be an option for some; use lowest effective dose23,24 |
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BP—blood pressure, CYP—cytochrome P450, ED—erectile dysfunction, MI—myocardial infarction, NAION—nonarteritic ischemic optic neuropathy, PDE5—phosphodiesterase 5, TCA—tricyclic antidepressant.