Udenafil (Zydena) and sildenafil (Viagra) are vasodilator drugs used in the treatment of ED (erectile dysfunction) in men. They are based on the same principle and have the same mechanism of action. However, they differ in pharmacodynamics and pharmacokinetics. This gives some ground for a little Zydena vs. Viagra battle. Udenafil is just another member of the PDE-5 inhibitor family, which also includes tadalafil, vardenafil, and avanafil. Another difference is that it is permitted in South Korea, the Philippines and Russia only, although it has been around since 2008. It hasn’t been approved by FDA yet, and it is not available in the United States or Europe.
Mechanism of Action
Both udenafil and sildenafil stimulate an erection through the inhibition of phosphodiesterase type 5 (PDE-5). It is a kind of an enzyme, which blocks the secretion of cyclic guanosine monophosphate (cGMP) and nitric oxide. Because these two substances relax the smooth muscle in the penis and ease the blood flow in the corpus cavernosum, blocking of PDE-5 results in higher nitric oxide and cGMP levels and, hence, better erection. It is noteworthy that this effect is only observable during sexual arousal. Therefore, the drugs actually work during a sexual intercourse only.
Sildenafil is the most renowned drug of the group, and its effectiveness is hardly doubted. However, there are reasons to believe that udenafil deserves less suspicion that it is facing now. Although it is not available in the civilized world, it is known for a much quicker onset of action and relatively long half-life.
The differences in pharmacodynamics and pharmacokinetics can be explained by differences in formula structure resulting in different selectivity levels: udenafil boasts a higher selectivity, and it targets PDE-5 more precisely. This results in quicker action and less pronounced side effects.
Another reason why the udenafil patent deserves decent mentioning is the drug’s ability to quickly bind with plasma proteins. This ability helps it retain the effect for up to 24 hours. For this reason, udenafil does not lose bioavailability when taken with fatty food or alcohol, like sildenafil does, and retains effectiveness.
Dosage and Administration
Both Zydena and Viagra are taken orally. Viagra comes in tablets, which are subdivided into 25 mg, 50 mg, and 100 mg tablets. For Zydena, there are two dose sizes: 10 mg and 20 mg.
Viagra should be taken without food and at least an hour prior to sexual activity. Zydena should be taken 30 minutes before a sexual intercourse. Unlike sildenafil, udenafil does not lose its bioavailability when taken with food, so it can be used effectively with or without food. Its effect is not influenced by alcohol either.
Precautions and Side Effects
Side effects and interactions are more pronounced with Viagra for reasons described above. The most common reactions include blushing, headache, hypotension, tachycardia, nausea, stuffy or runny nose, indigestion, angina, shortness of breath, poor color vision, confusion, etc. These side effects are typical of both drugs, but they are more likely to occur in Viagra users.
Sildenafil is not recommended for people, who have renal or hepatic insufficiency and cardiac disorders. Udenafil’s metabolism and ability to accumulate in the liver is not well studied yet; therefore, it should be used by people dealing with these disorders with caution too. It is highly advisable to consult a qualified doctor before using these vasodilator drugs. Neither should it be used by children under 18 years old.