Rigi10™ Malleable Penile Prosthesis
Also Known As
Penile Injection Therapy, Intracavernous Injection, Autoinjection Therapy for ED, Alprostadil penile injection, Papaverine penile injection, Phentolamine penile injection, Trimix injection, Bimix injection, Quadmix injection
Definition
Intracavernosal Injection (ICI) Therapy is a highly effective medical treatment for erectile dysfunction (ED), a condition characterized by the inability to achieve or maintain an erection firm enough for satisfactory sexual intercourse. This therapy involves the direct administration of a vasodilator medication into the corpora cavernosa of the penis.¹ The corpora cavernosa are two parallel, sponge-like cylindrical columns of erectile tissue located along the shaft of the penis. During sexual arousal, these tissues normally fill with blood, causing the penis to become erect.
In ICI therapy, the injected medication acts locally to relax the smooth muscle within the walls of the penile arteries and the trabecular smooth muscle of the corpora cavernosa.² This relaxation leads to vasodilation, a widening of the blood vessels, which significantly increases arterial blood flow into the penis. Simultaneously, the expansion of the corpora cavernosa compresses the penile veins (veno-occlusion), reducing the outflow of blood. This combined effect of increased inflow and decreased outflow results in a firm and sustained erection, typically occurring within 5 to 20 minutes after the injection, irrespective of sexual stimulation in many cases, although psychological arousal can enhance the response.³
The primary purpose of ICI therapy is to enable men who do not respond to or cannot tolerate oral ED medications, such as phosphodiesterase type 5 (PDE5) inhibitors (e.g., sildenafil, tadalafil), to achieve erections suitable for sexual activity.⁴ It is often considered a second-line therapy but can be a first-line option in certain specific patient populations, for example, in some cases of neurogenic ED.
Beyond its direct application for intercourse, ICI therapy also plays a crucial role in penile rehabilitation programs, particularly following radical prostatectomy (surgical removal of the prostate gland, often for cancer treatment). Regular use of ICI in such scenarios can help prevent cavernosal smooth muscle atrophy, reduce corporal fibrosis (scarring), and preserve overall tissue integrity within the penis, potentially improving the chances of recovering spontaneous erectile function over time.⁵
Clinical Context
Intracavernosal Injection (ICI) Therapy is a well-established and clinically significant treatment modality for erectile dysfunction (ED), particularly indicated when first-line oral therapies, such as phosphodiesterase type 5 (PDE5) inhibitors, prove ineffective, are contraindicated, or cause intolerable side effects.⁶ It is also a primary treatment option for ED of various etiologies, including psychogenic, neurogenic (e.g., spinal cord injury, multiple sclerosis, diabetic neuropathy), vasculogenic (e.g., atherosclerosis, hypertension, peripheral vascular disease), and mixed-etiology ED.
Patient selection is a critical aspect of ICI therapy. Ideal candidates are men with a confirmed diagnosis of ED who are motivated to use this treatment method and possess the necessary manual dexterity and visual acuity to perform self-injections accurately and safely. Alternatively, a willing and trained partner can administer the injections.⁷ Thorough patient education and counseling regarding the procedure, potential benefits, risks, and proper injection technique are paramount before initiating therapy.
Contraindications to ICI therapy include known hypersensitivity to the specific drug formulation, conditions that predispose to priapism (a prolonged erection lasting more than four hours) such as sickle cell anemia, multiple myeloma, leukemia, or other hematological disorders. Anatomical penile deformities, such as severe Peyronie’s disease, may also be a relative contraindication, although ICI can sometimes be used cautiously in such cases. The presence of a penile implant typically obviates the need for ICI.
The clinical process begins with an in-office test dose administered by a healthcare professional to determine the optimal drug and dosage for the individual patient, aiming for an erection sufficient for intercourse that lasts approximately one hour. Patients are then meticulously trained in self-injection techniques, including sterile preparation, site selection (typically the dorsolateral aspect of the proximal third of the penis, avoiding visible blood vessels, the urethra, and areas of fibrosis), and post-injection care.
Expected outcomes are generally favorable, with a rapid onset of erection (usually within 5-20 minutes) and high efficacy rates, often reported to be between 70% and 90%, depending on the specific medication (e.g., alprostadil, Trimix, Bimix) and the patient population.⁴ Common side effects are usually localized and transient, including mild to moderate penile pain or discomfort at the injection site, bruising, hematoma formation, and occasionally a burning sensation.
More serious, though less common, complications include the development of penile fibrosis or nodules with long-term, frequent use, and priapism, which is a medical emergency requiring prompt intervention to prevent ischemic damage to the cavernosal tissue.⁵ Regular follow-up appointments are essential to monitor treatment efficacy, assess for side effects, adjust medication dosages as needed, and reinforce proper injection techniques to minimize complications and ensure long-term treatment success.