What is the effect of vasoconstrictors on the penis?

From the Guidelines

Vasoconstrictors cause contraction of blood vessels in the penis, leading to reduced blood flow and resulting in penile detumescence or the inability to achieve an erection. Medications with vasoconstrictive properties include pseudoephedrine (30-60mg), phenylephrine (10mg), and ephedrine, which are sometimes used therapeutically to treat priapism (prolonged, painful erections lasting over 4 hours) 1. These medications work by stimulating alpha-adrenergic receptors in the penile vasculature, causing smooth muscle contraction in the arteries and reducing blood inflow to the erectile tissues. This mechanism is the opposite of how erectile dysfunction medications like sildenafil work, which promote vasodilation. Cold temperatures can also cause natural vasoconstriction in the penis. It's essential to note that some decongestants and blood pressure medications with vasoconstrictive properties may cause erectile dysfunction as a side effect. Patients with cardiovascular conditions should use vasoconstrictors cautiously due to potential systemic effects on blood pressure.

Some key points to consider:

• Vasoconstrictors can be used to treat priapism, but they may also cause erectile dysfunction as a side effect.
• The mechanism of vasoconstrictors is opposite to that of erectile dysfunction medications like sildenafil.
• Cold temperatures can cause natural vasoconstriction in the penis.
• Patients with cardiovascular conditions should use vasoconstrictors with caution.

The most recent and highest quality study on this topic is from 2009, which provides evidence on the effectiveness of PDE-5 inhibitors in improving erections and successful sexual intercourse 1. However, this study does not directly address the effect of vasoconstrictors on the penis. Therefore, the recommendation is based on the available evidence from earlier studies, which suggests that vasoconstrictors can cause contraction of blood vessels in the penis, leading to reduced blood flow and resulting in penile detumescence or the inability to achieve an erection.

From the FDA Drug Label

5.4 Extravasation and Tissue Necrosis with Intravenous Infusion ... vasa vasorum constriction with increased permeability of the vein wall, permitting some leakage. 5.5 Renal Impairment Epinephrine constricts renal blood vessels, which may result in oliguria or renal impairment.

The effect of vasoconstrictors, such as epinephrine, on the penis is not directly addressed in the provided drug label. Key points:

• The label discusses vasoconstriction in the context of peripheral blood vessels and renal blood vessels.
• There is no information about the specific effect of vasoconstrictors on the penis. 2

From the Research

Effect of Vasoconstrictors on the Penis

• Vasoconstrictors, such as phenylephrine, can induce contraction of the corpus cavernosum, which is the opposite effect of vasodilators like nitric oxide (NO) that are involved in penile erection 3.
• The use of vasoconstrictors, such as nitrates, is contraindicated with phosphodiesterase type-5 (PDE-5) inhibitors, such as sildenafil, as it can potentiate the hypotensive effect of the nitrate and lead to adverse cardiovascular effects 3.
• PDE-5 inhibitors, such as sildenafil, tadalafil, and vardenafil, work by enhancing the physiological process of penile erection during sexual arousal, and are effective in the treatment of erectile dysfunction (ED) 4, 3, 5, 6, 7.
• The mechanism of action of PDE-5 inhibitors involves the inhibition of the PDE-5 enzyme, resulting in an increase in cyclic guanosine monophosphate (cGMP) and smooth muscle relaxation in the penis, leading to increased blood flow and erection 4, 3, 5, 6, 7.

Interaction with Other Phosphodiesterases

• PDE-5 inhibitors have a high selectivity for the PDE-5 enzyme, but can also interact with other phosphodiesterases, such as PDE-6, which can lead to side effects like visual disturbances 6.
• The interaction of PDE-5 inhibitors with other phosphodiesterases can also affect their efficacy and safety profiles, and may lead to the development of new therapies or refinements to existing structures 6.

Clinical Implications

• The use of PDE-5 inhibitors, such as sildenafil, tadalafil, and vardenafil, is effective in the treatment of ED, but may have contraindications, such as the use of nitrates, and may require careful consideration of the patient's medical history and current medications 4, 3, 5, 7.
• The clinical update on PDE-5 inhibitors highlights their efficacy and safety profiles, and provides guidance on their use in the treatment of ED in different patient categories 7.