Intracavernous Therapy and Transurethral Gels Explained

Principles and Mechanism of Action of Intracavernous Therapy

Second- and third-line pharmacological therapy for the treatment of erectile dysfunction includes intracavernous injections, a highly effective alternative when oral inhibitors are ineffective, contraindicated, or cause intolerable adverse effects.

This approach involves the direct administration of vasoactive agents into the corpora cavernosa of the penis, which triggers rapid relaxation of the arterial smooth muscle and the subsequent blood flow necessary for rigidity.

Among the commonly used therapeutic options, alprostadil (prostaglandin E1) stands out and is available as monotherapy.

In addition, combination formulations known as Bimix (papaverine and phentolamine) and Trimix (papaverine, phentolamine, and alprostadil) are used.

These synergistic combinations enhance vasodilation through different biochemical pathways, allowing for reduced individual doses and a lower incidence of local pain, thereby achieving consistent erectile responses in complex cases of severe vascular, neurogenic, or psychogenic etiology in specialized clinical practice.

Administration, Dosage Adjustment, and Transurethral Alternatives

Proper administration of the injection requires prior training of the patient by the clinical team.

The injection is administered into the lateral aspect of the penile shaft, alternating sides with each administration and strictly avoiding the dorsal area—where neurovascular bundles run—as well as the ventral area to protect the urethra.

It is essential to conduct a dose titration process in a healthcare setting, starting with low concentrations to assess the hydraulic response and determine the exact amount that ensures a functional erection without excessive duration.

As a less invasive alternative, there are transurethral systems and topical alprostadil gels.

These devices deliver the drug into the urinary meatus or via a small suppository applied to the urethral mucosa, where it is absorbed into the adjacent cavernous tissues.

Although they are better tolerated because they avoid the use of a needle, they have a lower clinical efficacy rate and may cause a stinging sensation or bothersome local irritation.

Clinical Risks, Complications, and Management of Priapism

Despite its high success rate, local vasoactive therapy requires rigorous sexological and medical supervision due to its potential complications.

The most critical risk is priapism, defined as a prolonged, involuntary erection lasting more than three or four hours.

This condition constitutes a medical emergency, as prolonged blood stasis causes ischemia, endothelial damage, and irreversible tissue fibrosis, destroying future erectile capacity.

The patient must have a clear emergency protocol in place for blood aspiration or the instillation of alpha-adrenergic agonists.