Viagra generally works within 30 minutes, and its effect may be diminished if taken soon after a high fat meal (which may also delay how fast it works). For this reason, Viagra is best taken on an empty stomach.
Cialis generally works within 16 to 45 minutes, and its activity is not affected by food.
Cialis is the brand name for tadalafil and Viagra is the brand name for Sildenafil.
Both belong to a class of medicines known as phosphodiesterase type 5 (PDE5) inhibitors. PDE5 inhibitors work only in the presence of sexual stimulation, as they rely on the natural release of nitric oxide (NO), a chemical only released during sexual arousal. NO in turn activates other substances to relax the smooth muscle inside the penis to allow the inflow of blood and an erection to occur.
Cialis generally works within 16 to 45 minutes, and its activity is not affected by food.
Viagra generally works within 30 minutes, and its effect may be diminished if taken soon after a high fat meal (which may also delay how fast it works). For this reason, Viagra is best taken on an empty stomach.
References
- Viagra (sildenafil citrate) [Package Insert] Pfizer Laboratories Div Pfizer Inc 11/2015 https://www.drugs.com/pro/viagra.html
- Wright PJ. Comparison of Phosphodiesterase Type 5 (PDE5) Inhibitors. Int J Clin Pract. 2006;60(8):967-975. http://www.medscape.com/viewarticle/542736_4
- Drugs@FDA: FDA Approved Drug Products: https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=077342