Oral Pharmacological Treatment of Erectile Dysfunction:

Mechanism of Action and the Need for Erotic Stimulation

Phosphodiesterase type 5 inhibitors (PDE-5 inhibitors) constitute the first-line oral pharmacological treatment for erectile dysfunction.

Their mechanism of action is based on the selective inhibition of the PDE-5 enzyme, which is responsible for breaking down cyclic guanosine monophosphate (cGMP) in the smooth muscle cells of the corpora cavernosa.

By blocking this breakdown, they facilitate the sustained accumulation of cGMP and the subsequent vasodilation of the penile arteries mediated by nitric oxide.

It is vital to clarify in the field of sexology that these drugs are not aphrodisiacs nor do they automatically or spontaneously induce erections, as they unquestionably require prior and adequate erotic stimulation to trigger the full vasodilatory response.

Pharmacokinetic Profiles of the Main Molecules

Sildenafil was the first molecule marketed for erectile dysfunction. It has an onset of action of 30 to 60 minutes and a therapeutic window of four to five hours.

Its gastrointestinal absorption may be impaired or delayed if taken with large or high-fat meals, as well as with alcoholic beverages.

Vardenafil exhibits a temporal and metabolic profile very similar to that of sildenafil, offering an equivalent duration of action, although with subtle biochemical differences in its enzymatic potency.

In contrast, tadalafil stands out significantly for its prolonged half-life, maintaining its clinical effectiveness for up to 36 hours after administration.

Its absorption is not significantly affected by fatty foods or moderate alcohol consumption.

In addition to on-demand use, tadalafil allows for a daily dosing regimen at reduced doses of 5 milligrams.

This approach restores spontaneity to a couple’s intimate relationship, eliminates performance anxiety associated with planning sexual intercourse, and provides additional therapeutic benefits for men experiencing urinary symptoms due to benign prostatic hyperplasia.

Safety, Contraindications, and Management of Adverse Effects

Despite their high safety profile, the use of PDE-5 inhibitors always requires a rigorous prior medical eva luation.

The most critical absolute contraindication is concomitant administration with nitrates or nitric oxide donors, as the vasodilatory synergy can cause hemodynamic collapse and severe arterial hypotension.

Caution and a time interval between doses are also required in patients receiving treatment with alpha-blockers.

Side effects are typically brief, mild, and transient, resulting from PDE-5 inhibition in other vascular beds throughout the body.

The most common side effects include headache, facial flushing, nasal congestion, dyspepsia, and—particularly with tadalafil—muscle pain or lower back pain.