Vardenafil

Vardenafil is a prescription drug used for the treatment of erectile dysfunction (ED), a condition that is also addressed by drugs such as sildenafil (Viagra) and tadalafil (Cialis). The efficacy of vardenafil, sildenafil, and tadalafil all depend on their ability to inhibit the enzyme phosphodiesterase-5 (PDE-5), which plays a key role in regulating blood flow to and from the penis, as discussed below. Vardenafil is the active ingredient in Levitra, which is marketed by Bayer.

Source: Wikimedia Commons

Uses

Vardenafil is used the treatment of erectile dysfunction (ED) in adult males.

How Vardenafil is Taken

Vardenafil is available in oral tablets containing 2.5, 5, 10, or 20 mg of active drug. The recommended starting dose is 10 mg, taken one hour before sexual activity.

Thereafter, the dose may be increased to a maximum of 20 mg or decreased to 5 mg based on effectiveness and tolerability.

The maximum recommended dosing frequency is once per day.

How Levitra Works

Penile erection is caused by the relaxation of smooth muscle in the corpus cavernosum of the penis. See diagram below:

During sexual stimulation, nitric oxide is released from nerve endings and endothelial cells in the corpus cavernosum. Nitric oxide activates an enzyme called guanylate cyclase resulting in increased synthesis of cyclic guanosine monophosphate (cGMP) in the smooth muscle cells of the corpus cavernosum. The increased cGMP triggers smooth muscle relaxation, allowing increased blood flow into the penis, resulting in erection.

The level of cGMP in the penis is decreased by enzymes called phosphodiesterases (PDEs). The most abundant PDE in the human corpus cavernosum is the cGMP-specific phosphodiesterase type 5 (PDE-5).

Levitra works by inhibiting PDE-5, which results in enhanced erectile function due to increased amounts of cGMP in the penis.

How the Body Affects Levitra

Vardenafil is rapidly absorbed with peak circulating levels achieved between 30 minutes and 2 hours after dosing. Vardenafil is metabolized predominantly by the liver enzyme CYP3A4, and its metabolites are excreted predominantly in the feces (approximately 91-95% of the original dose) and to a lesser extent in the urine (approximately 2-6% of the original dose).

Side Effects

The most common side effects (occurring in >2% of treated patients) likely attributable to the use of Levitra are as follows:

• Headache
• Flushing
• Rhinitis ("runny nose")
• Dyspepsia (indigestion)
• Accidental injury
• Sinusitis (sinus inflammation)
• Flu-like syndrome
• Dizziness
• Increased creatine kinase (an enzyme released from muscle tissue)
• Nausea

Risks and Precautions

Levitra can cause sudden blood pressure drops if taken with medicines called nitrates. Sudden drops in blood pressure can cause dizziness, faintness, heart attacks or strokes.

Drug Interactions

The following drugs are known or likely to produce drug interactions with Levitra:

• Other medicines or treatments for ED
• Recreational drugs called “poppers” like amyl nitrate and butyl nitrate
• Prescription nitrates
• Alpha-blockers
• Anti-arrythmics like quinidine, procainamide, amiodarone and sotalol
• Ritonavir, indinavir, saquinavir or atazanavir
• Ketoconazole or itraconazole
• Erythromycin or clarithromycin

Effectiveness

One analysis of several studies shows vardenafil to be more effective than placebo in the treatment of ED.^[1]

References

1. ↑ http://cat.inist.fr/?aModele=afficheN&cpsidt=16302556

External Links

Levitra Website

FDA: Levitra Patient Information Sheet