Sildenafil (Viagra) and Tadalafil (Cialis): PDE5 Inhibitors for ED.
Gui í a de Salud Masculina
tadalafil (tadalafil) and sildenafil (sildenafil) are both drugs for the treatment of erectile dysfunction (ED) in men, but they are not recommended.
Pharmacological reasons
The mechanism is the same
-both of them belong to 5-phosphodiesterase (PDE5) inhibitors. PDE5 mainly exists in corpus cavernosum smooth muscle cells of penis. By inhibiting the activity of PDE5 enzyme, it can reduce the degradation of cyclic guanosine monophosphate (cGMP), relax the smooth muscle of corpus cavernosum and flow blood into penile tissue, thus promoting penile erection.
-the simultaneous use of these two drugs may excessively enhance the inhibitory effect on PDE5 and greatly increase the risk of adverse reactions.
Differences in pharmacokinetics may lead to superimposed risks
Absorption
-Sildenafil is absorbed rapidly after oral administration, and reaches the plasma peak concentration at 30-120min (median time 60min) after oral administration on an empty stomach. High-fat diet will delay its absorption.
The absorption of-Tadalafil is also rapid, reaching the plasma peak concentration 2 hours after oral administration on an empty stomach. Food has little effect on its absorption rate, but it will reduce the peak concentration by about 11%-15%.
Metabolism and excretion
-Sildenafil is mainly metabolized by liver cytochrome P450 3A4 (CYP3A4), and its metabolites have certain activity. Sildenafil and its metabolites are mainly excreted by feces and urine.
-Tadalafil is mainly metabolized by liver CYP3A4, a small part is metabolized by CYP2C9, mainly excreted by feces in the form of metabolites, and a small part is excreted by urine. If used together, it may interfere with each other in the metabolic process, affect their metabolic rate, and lead to abnormal increase of drug concentration in the body.
Risk of combined use
The risk of hypotension increased significantly
-A combination of the two drugs may over-dilate blood vessels, especially in the systemic vascular system, resulting in a significant drop in blood pressure, which may cause symptoms such as dizziness, dizziness and fainting. especially when standing up suddenly from sitting or lying position (postural hypotension).
Other adverse reactions worsened
-it may aggravate common adverse reactions such as headache, blushing, indigestion, stuffy nose and abnormal vision. These adverse reactions may not only affect the comfort of patients, but also affect their normal life and work in serious cases.
If a patient is not satisfied with the efficacy of an existing PDE5 inhibitor, they should consult their doctor instead of adding another drug on their own. The doctor will adjust the treatment plan according to the patient's specific conditions, such as age, health status, other drugs being taken, etc., and may consider changing the drug dose, treatment, or further examination to rule out other factors that may affect erectile function.