Prostaglandin E1 (PGE1), known generically as Alprostadil, is used therapeutically to induce vasodilation, which is the widening of blood vessels. As a synthetic version of a naturally occurring substance, Alprostadil is available in multiple forms. These include a sterile powder for intravenous infusion, a pellet for intraurethral administration, and a solution for self-administered intracavernosal injection. This article focuses on the safe and effective use of the injectable formulation, which requires careful preparation and technique.
Understanding Prostaglandin E1 and Its Function
Prostaglandin E1’s primary function is to relax smooth muscle tissue, which directly causes vasodilation and an increase in blood flow. This mechanism involves binding to specific cell receptors, which increases cellular levels of cyclic adenosine monophosphate (cAMP). Elevated cAMP levels trigger the relaxation of the smooth muscle and the expansion of the blood vessels.
The most common application for the self-administered injectable form of Alprostadil is to treat severe erectile dysfunction (ED). When injected directly into the corpora cavernosa, the drug locally relaxes the smooth muscle of the cavernosal arteries. This relaxation allows arterial blood to rapidly flow into the penile tissue, causing the penis to become rigid. The increased blood volume is then temporarily trapped by compressing the veins against the outer layer of the penis, a process known as the corporal veno-occlusive mechanism.
Alprostadil also has an application in neonates with specific congenital heart defects. In these infants, the drug is administered as a continuous intravenous infusion to keep the ductus arteriosus open. Maintaining the patency of this vessel ensures adequate blood flow until corrective surgery can be performed. This temporary measure utilizes the drug’s smooth muscle-relaxing property to maintain the open blood channel.
Guide to Intracavernosal Injection
Preparation begins with handling the medication, which often comes as a sterile powder requiring reconstitution with a provided diluent. Wash your hands thoroughly and use an alcohol swab to clean the vial’s rubber stopper before mixing. Follow the specific instructions for drawing up the correct amount of solution into the syringe.
The injection site must be chosen and cleaned, typically on the lateral side of the penile shaft between the base and the midpoint. To prepare the site, gently stretch the penis lengthwise against the thigh for stabilization and wipe the area with an alcohol swab, allowing it to dry fully. Alternate the injection site between the right and left sides of the penis with each use to help prevent localized tissue issues.
For administration, hold the syringe perpendicular to the injection site and insert the needle straight into the corpora cavernosa, avoiding visible veins. Push the plunger steadily and slowly to inject the solution over five to ten seconds. After withdrawing the needle, immediately apply gentle pressure to the injection site with an alcohol swab or sterile gauze until any bleeding has stopped.
Dosing must be determined by a healthcare provider, starting with a low dose and increasing gradually until the lowest effective dose is found. Initial test doses must be administered in a medical office setting to ensure safety and monitor the patient’s response. Never exceed the prescribed dose, and the injection should not be administered more than three times per week.
Safety Profile and Managing Adverse Effects
The most serious safety concern with Alprostadil injection is priapism, a prolonged erection lasting more than four hours. Priapism is a medical emergency that can lead to permanent tissue damage and loss of function if not treated promptly. If an erection persists beyond four hours, immediately seek medical assistance from your prescribing physician or an emergency room.
To minimize the risk of priapism, use the lowest effective dose determined during the dose titration process. Patients with conditions that predispose them to prolonged erections, such as sickle cell trait, multiple myeloma, or leukemia, should not use Alprostadil. People with anatomical deformities of the penis, including severe angulation or Peyronie’s disease, are also advised against using the injection due to increased complication risks.
Common side effects include localized pain at the injection site, bruising, and minor bleeding after the needle is withdrawn. There is also a risk of developing penile fibrosis. Regular physical examinations are recommended to detect early signs of fibrosis, and treatment should be discontinued if it develops.
Patients taking anticoagulant medications, such as warfarin or heparin, must use caution due to a higher chance of bleeding or bruising at the injection site. Store the medication according to the manufacturer’s directions, which often involves refrigeration for the unmixed product. Once mixed, the solution must be used immediately, and any unused portion must be properly discarded.