Filitra is available in different strengths, so the exact dosage should be confirmed from the packaging or prescription. Vardenafil is generally taken when needed, and it should not normally be taken more than once in 24 hours. Sexual stimulation is still necessary for the medicine to work. Common side effects can include headache, flushing, indigestion, nasal congestion, dizziness, and visual disturbances. Most are temporary. An erection lasting more than four hours, sudden hearing loss, or sudden vision loss requires urgent medical attention.