The common thing about Sildenafil, Tadalafil, and Vardenafil is that they are all meant to treat erectile dysfunction in men (the inability to erect or maintain an erection). They work by inhibiting phosphodiesterase type 5 (PDE5) enzymes. This results in an increase in cyclic guanosine monophosphate (cGMP) and increased blood flow in the penis, leading to an erection. The drugs also treat pulmonary arterial hypertension (a condition that results from narrowing of the pulmonary artery’s lumen) by widening the pulmonary artery’s lumen (vaso-dilation) resulting in normal blood pressure in that particular artery.
All the 3 drugs: Sildenafil, also referred to as Viagra; Tadalafil, marketed as Cialis, and Vardenafil which is marketed as Levitra have the similar working mechanisms. The difference arises in the reaction time. Vardenafil’s starts reacting after about 30 minutes to one hour. It has the ability to maintain an erection for a long period of time as compared to Sildenafil which starts reacting after about 30 minutes and maintains an erection up to about four hours. Tadalafil reacts faster and lasts longer as compared to both Sildenafil and Vardenafil. It starts working in the body after about 15 minutes and can last up to about 36 hours due to its high concentration. Due to its supernatural strength, people are always advised to use it once in a day.
Of all the three drugs, Vardenafil (Levitra) is considered to be the safest because of reported minimum side effects. However, if taken in wrong doses, it can lead to color vision problems.
Sildenafil, Tadalafil, and Vardenafil can all bring about negative side effects on users. The general side effects include headaches, impaired vision, and nasal congestion. In extreme cases, they can cause heart attack, loss of hearing, a strange continuous ringing in the ear, difficulty in breathing, or uncomfortable muscular pain.
The general contraindications of the drugs are that they should not be taken by any one suffering from the following health complications:
- Kidney and liver problems
- Hypotension ( low blood pressure)
- Recent heart attack
- Recent stroke
- Hereditary degenerative retinal disorders
In addition, it is not recommended or advisable for people taking nitric oxide donor drugs, nitrates, or organic nitrites should to use these drugs.