Viagra (Sildenafil) and Cialis (Tadalafil) are both popular medicines that help men get rid of erectile dysfunction. However, Viagra is used to treat ED only, while Cialis can also be used to treat BPD (benign prostatic hyperplasia).
Mechanism of Action and Effect Comparison
Sildenafil comes in the form of blue diamond-shaped film-coated tablets. They differ in dosage (25 mg, 50 mg, 100 mg) and have a VGR engraving on one side and that of a tablet dose on the other.
The drug belongs to the class of phosphodiesterase type 5 (PDE-5) inhibitors. Its mechanism of action consists in maintaining nitric oxide levels in the corpora cavernosa through blocking the PDE-5. Nitric oxide (NO) is secreted during sexual arousal. It relaxes penile muscles and stimulates the blood flow in the corpora cavernosa (two sponge-like bodies located in the penis), helping the blood fill them faster and better.
Tadalafil is manufactured as almond-shaped yellow film-coated tablets with a ‘C’ (Cialis) and tablet dose engraved on each tablet (for example, C10 for a 10 mg tablet). They differ in dosage as well (2.5 mg, 5 mg, 10 mg, 20 mg).
Its mechanism of action is exactly the same as the one of Sildenafil, as it inhibits PDE-5 and stimulates the production of NO. However, Tadalafil is known to act a bit slower: while it takes about 30 minutes for Sildenafil to produce the effect, Tadalafil starts working about an hour or two after administration. On the other hand, the effect of Tadalafil is long-lasting: while Sildenafil effect continues for 4 to 5 hours, Tadalafil keeps working from 12 to 36 hours. It has been deservedly nicknamed the ‘weekend pill’, as you do not have to schedule your sexual activity.
Important note: Neither Cialis nor Viagra will affect your sexuality in general. They do not give you an extra degree of arousal. All they do is target the muscular system of the penis and stimulate blood circulation in the corpora cavernosa, providing you with a better erection.
Dosage and Administration Comparison
Unlike Viagra, Cialis can be used both on as-needed and daily basis, thanks to its day-long effect. The starting dose is usually 5 mg or 10 mg, which can be reduced or increased based on how well it works and whether it triggers side effects. If used on a daily basis, doctors advise to start with 2.5 mg. If used for BPH treatment, the starting dose is 5 mg.
Mostly, Sildenafil is recommended for as-needed use. The starting dose is 50 mg, and it should be taken approximately an hour before a sexual intercourse. Doctors recommend their patients to increase the dose if the current one seems insufficient, or reduce it if the side effects get too severe. Sildenafil is to be taken once a day only.
The effect of Viagra is more food-dependent than that of Cialis. It may be reduced if you take it soon after a good meal. Particularly, it is not advisable to combine Sildenafil with fatty food and grapefruit juice. Tadalafil effect is not influenced by food that much.
Interactions, Precautions and Side Effects
Co-administering Tadalafil and Sildenafil with other medications requires a very cautious approach. Neither should be combined with:
- Other anti-impotence drugs;
- Anti-hypertension drugs;
- Anti-HIV/AIDS drugs;
Neither Cialis nor Viagra are recommended for patients who have just recovered from:
- Heart failure;
- Kidney and/or liver problems;
The most frequently occurring side effects after the intake of both are the following:
- Muscular pain;
- Prolonged erection;
- Runny/stuffy nose;
- Diarrhea (Viagra);
- Poor sleep (Viagra);
- Vision and hearing problems (Viagra);
- Difficulty urinating (Viagra).