Alprostadil
A medication that treats erectile dysfunction by relaxing the blood vessels in the penis, allowing blood to flow in and create an erection. Unlike pills that require arousal to work, this works directly at the injection or application site — you don't need to be in the mood. Available as an injection into the penis or as a small pellet inserted into the urethra.
Dosage
Intracavernosal: 2.5-40 mcg per injection. MUSE: 125-1000 mcg
Dosages shown are for research reference only. Always consult a qualified healthcare provider.
Administration
Intracavernosal injection or urethral suppository
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Effects
Erectile Function
Direct local vasodilation produces erection independent of arousal or nerve function.
Blood Flow
Directly relaxes blood vessel walls to increase local blood flow, independent of arousal or nerve signals.
Wound Healing
Improved microcirculation supports tissue repair in peripheral vascular conditions.
Mechanism of Action
Alprostadil is synthetic prostaglandin E1 (PGE1), a 20-carbon oxygenated fatty acid derived from dihomo-gamma-linolenic acid (DGLA) through the cyclooxygenase pathway. It acts locally on penile vascular and trabecular smooth muscle through two prostaglandin E receptor subtypes: EP2 and EP4, both of which are Gs-coupled GPCRs that increase intracellular cAMP upon activation.
Elevated cAMP activates protein kinase A (PKA), which phosphorylates multiple targets in smooth muscle cells to produce relaxation. PKA phosphorylates myosin light chain kinase (MLCK), reducing its affinity for the calcium-calmodulin complex and decreasing its ability to phosphorylate myosin light chains — the final step in smooth muscle contraction. PKA also activates calcium-ATPase pumps and opens potassium channels, reducing intracellular calcium concentration. The net effect is relaxation of both the helicine arterioles (which supply blood to the corpora cavernosa) and the trabecular smooth muscle (which forms the spongy erectile tissue). As these relax, blood flows into the sinusoidal spaces of the corpora cavernosa, expanding the tissue against the tunica albuginea and compressing the subtunical veins — trapping blood and producing an erection.
The critical distinction of alprostadil's mechanism is its direct, local action independent of central sexual arousal pathways and independent of nitric oxide. PDE5 inhibitors (sildenafil, etc.) work by preventing cGMP breakdown downstream of nitric oxide release, which requires sexual arousal to generate the initial NO signal. Alprostadil generates its own second messenger (cAMP) at the injection site regardless of arousal state, which is why it produces erections reliably even in patients with neurogenic erectile dysfunction (spinal cord injury, radical prostatectomy) where the nerve-mediated NO pathway is damaged. The extremely rapid pulmonary metabolism (80% cleared in a single pass through the lungs) ensures that systemic effects are minimal when administered locally.
Regulatory Status
FDA approved. Caverject/Edex (injection), MUSE (urethral). Prescription required. Also available compounded in combination formulations (TriMix).
Risks & Safety
Common
penile pain (about 37% with injection, 30% with urethral pellet), erection lasting too long, burning in the urethra (with pellet), minor bleeding (with pellet).
Serious
priapism — an erection lasting more than 4 hours is a medical emergency and needs immediate treatment to prevent permanent damage; repeated injections can cause scarring and curvature of the penis.
Rare
penile fracture, infection at the injection site. Should not be used if you have sickle cell disease or bleeding disorders.
Compare Alprostadil With
Research Papers
30Published: November 6, 2025
AI Summary
Researchers investigated how chloride channels are regulated in a rabbit model of proliferative vitreoretinopathy. The abstract describes the study aim; full results would clarify the mechanism and potential treatment targets.
Published: January 29, 2026
AI Summary
Researchers evaluated the cost-effectiveness of different treatments for chronic constipation in Japan. The work aims to guide clinicians toward the most efficient treatment options.
Published: October 20, 2025
AI Summary
Researchers compared the cost-effectiveness of elobixibat, linaclotide, and lubiprostone for chronic idiopathic constipation in Japan. The work quantifies both clinical and socioeconomic value of these treatments.
Published: October 14, 2025
AI Summary
In a family with a genetic kidney disease, alprostadil improved some cell features but worsened others, while an EGFR inhibitor more effectively reversed the disease signature. EGFR inhibition may be a better therapeutic strategy than alprostadil for this condition.
Published: July 24, 2025
AI Summary
Evidence-based guidelines provide 34 recommendations for diagnosing and managing functional constipation, including the use of lubiprostone and linaclotide. The guidelines help clinicians and patients make informed treatment decisions.
Published: April 24, 2025
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A review outlines drug options for IBS with constipation, including lubiprostone, linaclotide, and others. Effective management requires a personalized approach based on symptoms and patient goals.
Published: May 27, 2025
AI Summary
Researchers compared healthcare use and costs among Medicare patients taking linaclotide, lubiprostone, or plecanatide for constipation. The work informs cost-effectiveness of these treatments in older adults.
Published: December 22, 2025
AI Summary
Researchers tested whether insulin aspart, lidocaine, alprostadil, and vancomycin can be safely mixed with parenteral nutrition in critically ill newborns. The abstract describes the study aim; results would guide safe IV administration.
Published: November 4, 2024
AI Summary
Abstract too short to summarize.
Published: October 24, 2024
AI Summary
Abstract too short to summarize.
Published: October 7, 2024
AI Summary
PGE2 and related compounds promoted growth of thyroid cancer cells through specific receptor subtypes and STAT5a signaling. The findings could inform how prostaglandins influence tumor cell proliferation.
Published: January 1, 2024
AI Summary
A systematic review compared the efficacy, safety, and quality-of-life impact of lubiprostone, linaclotide, and elobixibat for chronic constipation. The work helps clinicians choose among these options.
Published: December 12, 2023
AI Summary
Combining GM-CSF and PGE1 converted leukemia cells into immune-stimulating cells that triggered antileukemic responses in blood and bone marrow. The approach could help stabilize remission in acute myeloid leukemia.
Published: November 28, 2023
AI Summary
Repeated injections of a Muse cell product were safe and well tolerated in five ALS patients. Some showed slower disease progression; a larger trial is needed to confirm efficacy.
Published: March 10, 2024
AI Summary
Researchers evaluated whether Muse cells given intravenously restore erectile function in rats with nerve injury. The abstract describes the study aim; full results would clarify therapeutic potential.
Published: August 10, 2023
AI Summary
Researchers tested whether Muse cells can prevent lethal gut damage from high-dose radiation. The abstract describes the study aim; full results would clarify intestinal regeneration mechanisms.
Published: December 1, 2023
AI Summary
Lubiprostone, identified by AI for repurposing, reduced kidney fibrosis in lab and animal models by blocking several profibrotic pathways. The drug could offer a new treatment for chronic kidney disease.
Published: December 15, 2023
AI Summary
Fat-derived Muse cells reduced inflammation after spinal cord injury more effectively than bone marrow–derived Muse cells. Fat-derived cells may be a better option for anti-inflammatory therapy.
Published: December 14, 2022
AI Summary
Blocking heat shock protein 70 enhanced PGE1-driven IL-6 production in bone cells through p38 MAPK. The findings suggest HSP70 helps regulate bone remodeling responses to prostaglandins.
Published: December 1, 2022
AI Summary
Prostaglandin E1 and other metabolites emerged as potential blood markers for latent tuberculosis. The work could support earlier diagnosis and monitoring of TB progression.
Published: October 13, 2022
AI Summary
Muse cells from amniotic membrane showed broader differentiation potential than bone marrow Muse cells, resembling early pluripotent stem cells. These cells could be a useful non-tumorigenic stem cell source.
Published: January 11, 2023
AI Summary
Researchers explored whether the stem cell marker SSEA-3 influences Muse cell behavior and FGF2 signaling. The abstract describes the study aim; full results would clarify marker function.
Published: October 5, 2022
AI Summary
Stem cells rapidly differentiated by engulfing dying differentiated cells and taking up their contents. The finding reveals a simple mechanism for fast cell fate change without long cytokine exposure.
Published: December 20, 2022
AI Summary
Exenatide reduced fat cell formation, raised CTRP3, and triggered apoptosis in fat cells. The work supports exenatide as a potential obesity treatment through multiple mechanisms.
Published: November 11, 2022
AI Summary
A review assessed the safety and efficacy of anifrolumab, which blocks type 1 interferon, in lupus patients. The work helps clinicians evaluate this newer treatment option.
Published: July 15, 2022
AI Summary
Pre-treating stem cells with PGE1 improved their survival and homing in rats with pulmonary hypertension. The approach could enhance stem cell therapy for this condition.
Published: October 29, 2022
AI Summary
Misoprostol did not cause excessive uterine inflammation in mares when given before breeding or after embryo flushing. The findings support its use for suspected uterine tube obstruction.
Published: May 14, 2022
AI Summary
Researchers evaluated whether combining epalrestat and alprostadil improves diabetic kidney disease and reduces fibrosis and inflammation. The abstract describes the study aim; full results would clarify efficacy.
Published: December 28, 2021
AI Summary
PGE2 and PGE1 suppressed nerve growth factor in disc cells by boosting DUSP-1 and dampening MAPK signaling. The mechanism could explain how prostaglandins reduce disc-related back pain.
Published: July 15, 2022
AI Summary
Researchers investigated the anti-inflammatory effects of a Lactobacillus strain in immune cells. The abstract describes the study aim; full results would clarify eicosanoid regulation.
Frequently Asked Questions
What is Alprostadil?
A medication that treats erectile dysfunction by relaxing the blood vessels in the penis, allowing blood to flow in and create an erection. Unlike pills that require arousal to work, this works directly at the injection or application site — you don't need to be in the mood. Available as an injection into the penis or as a small pellet inserted into the urethra.
What is Alprostadil used for?
A medication that treats erectile dysfunction by relaxing the blood vessels in the penis, allowing blood to flow in and create an erection. Unlike pills that require arousal to work, this works directly at the injection or application site — you don't need to be in the mood. Available as an injection into the penis or as a small pellet inserted into the urethra.
What is the dosage for Alprostadil?
Intracavernosal (Caverject): 2.5-40 mcg per injection, dose titrated in physician's office. Urethral suppository (MUSE): 125-1000 mcg per application. Maximum 1 dose per 24 hours, 3 doses per week.
What are the side effects of Alprostadil?
Common: penile pain (about 37% with injection, 30% with urethral pellet), erection lasting too long, burning in the urethra (with pellet), minor bleeding (with pellet). Serious: priapism — an erection lasting more than 4 hours is a medical emergency and needs immediate treatment to prevent permanent damage; repeated injections can cause scarring and curvature of the penis. Rare: penile fracture, infection at the injection site. Should not be used if you have sickle cell disease or bleeding disorders.
How does Alprostadil work?
Alprostadil is synthetic prostaglandin E1 (PGE1), a 20-carbon oxygenated fatty acid derived from dihomo-gamma-linolenic acid (DGLA) through the cyclooxygenase pathway. It acts locally on penile vascular and trabecular smooth muscle through two prostaglandin E receptor subtypes: EP2 and EP4, both of which are Gs-coupled GPCRs that increase intracellular cAMP upon activation. Elevated cAMP activates protein kinase A (PKA), which phosphorylates multiple targets in smooth muscle cells to produce relaxation. PKA phosphorylates myosin light chain kinase (MLCK), reducing its affinity for the calcium-calmodulin complex and decreasing its ability to phosphorylate myosin light chains — the final step in smooth muscle contraction. PKA also activates calcium-ATPase pumps and opens potassium channels, reducing intracellular calcium concentration. The net effect is relaxation of both the helicine arterioles (which supply blood to the corpora cavernosa) and the trabecular smooth muscle (which forms the spongy erectile tissue). As these relax, blood flows into the sinusoidal spaces of the corpora cavernosa, expanding the tissue against the tunica albuginea and compressing the subtunical veins — trapping blood and producing an erection. The critical distinction of alprostadil's mechanism is its direct, local action independent of central sexual arousal pathways and independent of nitric oxide. PDE5 inhibitors (sildenafil, etc.) work by preventing cGMP breakdown downstream of nitric oxide release, which requires sexual arousal to generate the initial NO signal. Alprostadil generates its own second messenger (cAMP) at the injection site regardless of arousal state, which is why it produces erections reliably even in patients with neurogenic erectile dysfunction (spinal cord injury, radical prostatectomy) where the nerve-mediated NO pathway is damaged. The extremely rapid pulmonary metabolism (80% cleared in a single pass through the lungs) ensures that systemic effects are minimal when administered locally.
How is Alprostadil administered?
Alprostadil is administered via intracavernosal injection or urethral suppository.
What is the half-life of Alprostadil?
The half-life of Alprostadil is 5-10 minutes (rapidly metabolized in the lungs).
Is Alprostadil legal?
FDA approved. Caverject/Edex (injection), MUSE (urethral). Prescription required. Also available compounded in combination formulations (TriMix).
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