PDE5 inhibitors, such as the potent drug fildena 100 mg, are available. Sildenafil citrate, the drug's active component, promotes a normal response to sexual stimulation by boosting blood flow to the penile area. Stated differently, it facilitates the relaxation of blood vessels within the male reproductive organ, hence increasing blood flow and erection. A meal heavy in fat may cause the medication to take longer to start acting. Before engaging in any sexual activity, take sildenafil at least 30 minutes but no more than 4 hours in advance. Take only once a day, please. Never take any additional medication without first talking to your doctor. Should you be allergic to sildenafil citrate, avoid taking Fildena.