Papaverine is a vasodilator, a medication that helps widen blood vessels. It is used in the treatment of erectile dysfunction (ED) by promoting increased blood flow to the penis to induce an erection.
Understanding Papaverine’s Action
Papaverine works by relaxing the smooth muscles within the penis, specifically in the corpus cavernosum. This relaxation expands blood vessels, allowing a greater influx of blood into the penile tissues. The increased blood flow and volume then compress venous channels, trapping blood within the penis and resulting in an erection. Papaverine achieves this through its action as a non-specific phosphodiesterase inhibitor, which elevates levels of cyclic AMP and cyclic GMP, though its exact mechanism is not fully understood.
Typical Dosing and Administration
Papaverine for ED is administered via intracavernosal injection, directly into the spongy tissue of the penis. Initial dosing begins low and is gradually increased under medical supervision to determine the most effective amount for each patient.
The typical effective dose range is between 2.5 to 60 milligrams (mg). A common starting dose for most cases of ED is around 15 mg. Individuals with psychogenic ED may respond to lower doses, while those with vasculogenic ED often require higher doses. For men with spinal cord injuries, a starting dose of 5 mg may be recommended.
Injections should not exceed more than once daily or three times per week, with a minimum of 24 hours between doses. The first injection must be performed by medically trained personnel.
Important Side Effects and Warnings
Common side effects associated with papaverine injections include localized reactions such as pain, bruising, or mild swelling at the injection site. Some individuals may also experience a tingling sensation at the tip of the penis.
More serious side effects can occur, including priapism, a prolonged erection lasting more than four hours. This condition is dangerous as it can cut off blood supply to the penis and lead to permanent damage if not treated promptly. Fibrosis, or the formation of scar tissue and lumps within the penis, is another potential serious complication that can result in penile curvature. Hypotension, or low blood pressure, is also a possible systemic side effect. Any erection lasting over four hours or becoming painful requires immediate medical attention.
Papaverine’s Role in ED Treatment
Papaverine is considered a second-line or third-line treatment for erectile dysfunction. It is often utilized when oral medications, such as PDE5 inhibitors, are ineffective, contraindicated due to other health conditions, or cause intolerable side effects. The use of papaverine requires patient education and training for self-administration. While it can be used alone, papaverine is sometimes combined with other medications like phentolamine or alprostadil to enhance efficacy.