Malaysia has an aging population. Soon we will join the ranks of developed countries in terms of its demographic characteristics. This was pointed out by Dato Dr Tan Hui Ming, a consultant urologist with SJMC, during the launch of Levitra(ED drug) recently. Interestingly, it is the men that is not coping well with aging, that is they are not aging healthily. Several contributors include the consumption of alcohol, smoking and their reluctance to seek early medical attention. This increases the incidences of cardiovascular morbidity, cancer, diabetes and hyperlipidemic states. All this contributes to the higher rate of mortality in a younger age group among men leading to their declining numbers as the age increases.
Even erectile dysfunction it appears is prevalent among our aging men. Nevertheless, not many seek medical attention and even less are taking treatments for erectile dysfunction(ED). The treatment of ED has revolutionised since the introduction of oral medications that is the PDE-5 inhibitors. Sildenafil(viagra) was the first of its kind. Levitra (vardenafil) can be considered as a second generation PDE-5 inhibitor.
Among the advantages of Levitra over Viagra is its specificity for the PDE-5 enzyme. This specificity reduces side effects associated with viagra especially blue-green color vision associated with inhibition of PDE-6 enzyme in the eye. Although Levitra also inhibits the PDE-11 enzyme, the function of this enzyme is unknown. Side effects from trials include benign conditions eg headaches , flushes, nasal congestion and an upset stomach. The onset of action(ie the time to achieving an erection) for Levitra could also be as early as 10-15 minutes with variations among patients.
According to the PROVEN study, Levitra was effective in about 46% of the men who were previously unsuccessful with Viagra. However, note that there are no head to head comparison studies to date.
Below is an article I wrote on MMR previously
|Erectile Dysfunction(ED) : Sildenafil vs tadalafil vs vardenafil
ED is an under-discussed problem between patients and their doctors. Unfortunately most doctors themselves are uncomfortable discussing about sexual problems with their patients. The prevalence of ED in Malaysia is not known but I would suspect little difference with other countries. In the United States, up to 26% of males are said to be suffering from moderate to severe forms of ED. The aetiology of ED is numerous from organic (eg vascular compromise due to smoking or diabetes) to psychogenic problems. Some have mixed aetiologies.
The treatment of ED has revolutionised over the past decade with the introduction of Sildenafil (Viagra). Since its advent, second generation ED drugs have surfaced namely talalafil (Cialis) and Vardenafil(levitra). These are drugs that competitively inhibit the enzyme Phosphodiesterase (PDE), specifically PDE-5 which is mainly found in smooth muscle and vascular tissues. For the benefit of all, here is some physiology about erection.
Upon sexual stimulation, the parasympathetic nerves release nitric oxide which then diffuses into smooth muscle cells before binding to enzyme guanylate cyclase there. Guanylate cyclase converts GTP to cGMP. cGMP then binds to Protein Kinase G which then causes smooth muscle cells to relax allowing blood to flow through the sinosoids of the corpus cavernosum producing an erection. PDE-5 causes the breakdown of cGMP. Therefore by inhibiting PDE-5, cGMP could produce its effects for a longer period of time.
With the recent introduction of tadalafil(Cialis) in Malaysia, which would be a better choice? Viagra or Cialis? There are at this moment no comparator studies between the two. So no one can say one is better than the other. But doubleblind placebo controlled studies have shown both to be efficacious.
Viagra has a shorter half life (4-6 hours) and its onset of action is approximately 30 minutes. Studies have shown and proven its safety , even in heart patients. But side effects are dose dependant ie the higher the prescribed dose, the greater its side effects. Because Viagra inhibits PDE-6(present in the eye) at high doses, it could produce colour visual disturbances. Other side effects, headaches, diarrhoea and flushing are similar with other groups of PDE inhibitors as well. It is contraindicated in patients using nitrates (also a vasodilator) and caution in patients with heart disease. Although data from some studies actually show a cardioprotective effect from Viagra!
Vardenafil(Levitra) has a similar profile to sildenafil due to its slosely similar chemical structure.
Cialis on the other hand,which has a slightly different chemical structure, has a longer half life, up to 24 hours. It is said to be more specific for PDE-5 although it is known to also inhibit PDE-11 which is found in the testes and heart. The effect of this is unknown pending post marketing studies. Due to its long half life, the chances of side effects from it is much higher. However the benefit of tadalafil is said to be that, it is not significantly affected by renal or liver impairment. The onset is also claimed to be as fast as 15 minutes in responsive patients!!
The verdict? Personally, i would prefer a more well tested drug ie Viagra. The shorter half life is more comforting as compared to a longer one. Until further studies show a superior safety profile of Cialis, Viagra would be the preferred choice. Perhaps a head to head comparator study needs to be done, pitching Pfizer, Bayer and Lilly! That would certainly be the next big thing … after Lord of the Rings!
With new information on Levitra, it probably holds an edge over Viagra in terms of its onset of action and its safety profile. Cialis is less enticing due to its long duration of action. However, all 3 drugs do work and it boils down to patient preferences. As pointed out, a good sexual life is not all just about achieving an erection!
Lastly, healthy aging involves a healthy and fulfilling sexual life! Levitra is certainly a welcomed addition to the armamentarium of ED treatment.