How Does Vitaros Cream Work in the Body
Chemical Composition, Mechanism of Action & Metabolic Effects Explained
Key Takeaways: How Vitaros Cream Works
- Active ingredient: Alprostadil (synthetic prostaglandin E1)
- Primary action: Relaxes penile smooth muscle by increasing cAMP
- Target receptors: EP2 and EP4 receptors on vascular endothelium
- Onset: Erection begins 5–30 minutes after application
- Duration: Local effect lasts 1–2 hours
- Unique feature: Applied directly to urethral opening, minimal systemic absorption
Vitaros cream (alprostadil) is a locally acting treatment for erectile dysfunction. It bypasses the digestive system and works directly on penile tissue, making it an option for men who cannot take oral PDE5 inhibitors. Below we explain the science behind how it creates an erection.
Important Medical Advice
If you experience an erection lasting more than 4 hours (priapism), sudden dizziness, fainting, or severe penile pain after using Vitaros, seek immediate medical attention. Do not combine with other ED treatments unless approved by your doctor.
Chemical Composition & Molecular Structure of Vitaros Cream
Vitaros contains the active ingredient alprostadil, a synthetic version of prostaglandin E1 (PGE1). Its molecular formula is C20H34O5 (molecular weight 354.48 g/mol). The cream also includes innovative permeation enhancers to facilitate absorption through the urethral mucosa.
Formulation details
Alprostadil 3 mg/g (0.3% w/w)
Each single‑use AccuDose delivers 300 micrograms of alprostadil in 100 mg cream.
Dodecyl 2‑N,N‑dimethylaminopropionate hydrochloride (DDAIP·HCl)
A penetration enhancer that temporarily increases urethral epithelial permeability, allowing alprostadil to reach the corpus spongiosum.
Ethyl laurate, ethanol, hydroxypropyl guar gum
These provide a creamy consistency and help solubilise alprostadil while maintaining stability.
Physicochemical properties
| Property | Value | Clinical relevance |
|---|---|---|
| logP (octanol/water) | 2.9 | Moderate lipophilicity favours mucosal penetration |
| pKa (acidic) | 4.9 | Partly ionised at urethral pH, aiding solubility |
| Melting point | 115–116 °C | Stable at room temperature when stored properly |
🗒️ Pharmaceutical insight: The DDAIP·HCl enhancer is crucial – it reversibly disrupts tight junctions in the urethral lining, enabling alprostadil to diffuse into the corpus spongiosum and reach the cavernosal arteries.
Mechanism of Action: How Vitaros Cream Creates an Erection
Alprostadil mimics naturally occurring prostaglandin E1. After urethral absorption, it binds to specific prostanoid receptors on penile smooth muscle cells and endothelial cells.
Step‑by‑step pathway
- Receptor activation: Alprostadil binds to EP2 and EP4 receptors (Gs‑coupled).
- cAMP rise: Activation of adenylate cyclase increases intracellular cyclic AMP.
- Kinase activation: cAMP activates protein kinase A (PKA).
- Calcium decrease: PKA phosphorylates ion channels and pumps, reducing calcium influx and enhancing calcium reuptake into sarcoplasmic reticulum.
- Smooth muscle relaxation: Lower cytosolic calcium relaxes the trabecular smooth muscle of the corpora cavernosa.
- Vasodilation: Arterial inflow increases, expanding the sinusoidal spaces – an erection occurs.
🗒️ Physiological note: Unlike oral PDE5 inhibitors, Vitaros does not depend on nitric oxide or sexual stimulation – it works directly on the smooth muscle, although arousal can enhance the response.
Receptor Binding and Cellular Pathways of Vitaros Cream
Alprostadil has high affinity for prostaglandin E receptors EP2 and EP4. These receptors are abundant in penile vasculature and corpus cavernosum.
EP2 receptor
Gs protein → adenylate cyclase → cAMP ↑ → PKA activation → smooth muscle relaxation.
EP4 receptor
Similar Gs coupling; also activates PI3K/Akt pathway, contributing to endothelial protection and vasodilation.
Direct effect on arteries
Alprostadil also inhibits noradrenaline release from sympathetic nerve endings, reducing vasoconstriction.
The overall effect is a rapid, localised increase in penile blood flow with minimal influence on systemic vasculature due to rapid local metabolism.
Metabolic Effects and Duration in the Body
Once alprostadil enters the systemic circulation (a small fraction), it is rapidly metabolised. However, its action is primarily local.
Fate of alprostadil after urethral application
- Local tissue: Approximately 80% is metabolised within the penile urethra by 15‑hydroxyprostaglandin dehydrogenase.
- Systemic absorption: Less than 20% reaches circulation; peak plasma concentrations occur within 30 minutes but are very low (picomolar range).
- Pulmonary passage: Any absorbed alprostadil is 70‑90% metabolised during one pass through the lungs (via oxidation).
- Half‑life: The terminal half‑life of metabolites is about 5‑10 minutes; no accumulation occurs.
The duration of penile rigidity is typically 1–2 hours, corresponding to the time the drug remains in the local tissue.
Absorption, Distribution & Systemic Exposure of Vitaros Cream
Absorption
Via urethral mucosa; onset 5–30 min. Bioavailability ~0.5% (very low systemic exposure).
Distribution
Minimal due to rapid local metabolism. Volume of distribution not clinically relevant.
Elimination
Metabolites (mainly 15‑keto‑PGE1 and 13,14‑dihydro‑15‑keto‑PGE1) excreted in urine (88%) and faeces (12%).
Factors influencing absorption
- Urination after application: Can wash out the cream – wait at least 30 minutes.
- Retraction of foreskin: Ensures cream reaches the meatus.
- Warming the AccuDose: Improves cream flow and absorption.
Clinical Efficacy and Onset of Erection with Vitaros Cream
In clinical studies, Vitaros produced erections sufficient for intercourse in approximately 65‑70% of men with ED of various causes. Onset is predictable:
| Parameter | Typical value | Note |
|---|---|---|
| Onset | 5–30 minutes | Faster than oral sildenafil |
| Duration | 1–2 hours | May persist after ejaculation |
| Erection hardness | Sufficient for penetration | Depends on correct application |
| Partner effects | Mild vaginal burning in ~5% | Use condom if partner is pregnant or at risk |
🗒️ Clinical pearl: Patients with mild‑to‑moderate ED often respond best. Those with severe vascular damage may require higher strength (3 mg/g) and careful dose titration by a doctor.
Vitaros Cream FAQs
How quickly does Vitaros cream start working?
Vitaros usually produces an erection within 5 to 30 minutes after application. You can engage in foreplay during this time to enhance the response.
Can I use Vitaros with other ED medications like Viagra?
No, combining Vitaros with oral PDE5 inhibitors or other ED treatments has not been studied and may increase the risk of priapism, fainting, and low blood pressure.
What should I do if my erection lasts more than 4 hours?
This is a medical emergency (priapism). Contact your doctor immediately or go to A&E. Delayed treatment can cause permanent damage to penile tissue.
Can my partner be affected by the cream?
Some partners report mild vaginal burning or itching. If your partner is pregnant, breastfeeding, or of childbearing potential, you must use a condom to avoid exposure.
Is Vitaros safe for men with heart conditions?
Vitaros has minimal systemic absorption, so it may be safer than oral ED pills for some heart patients. However, sexual activity itself carries cardiac risk. Always get medical clearance first.
Need a Prescription for Vitaros Cream?
If you think Vitaros might be right for you, speak with a UK‑registered doctor through a confidential online consultation.
Secure Prescription & Next‑Day Delivery
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Medical Content Manager
Nabeel is a co-founder, and medical content manager of Chemist Doctor. He works closely with our medical team to ensure the information is accurate and up-to-date.
Medical Doctor
Dr. Feroz is a GMC-registered doctor and a medical reviewer at Chemist Doctor. He oversees acute condition and urgent care guidance.
Medical Director
Usman is a co-founder, and medical director of Chemist Doctor. He leads the organisation's strategic vision, bridging clinical and operational priorities.
Review Date: 15 February 2026
Next Review: 15 August 2026
Published on: 15 February 2026
Last Updated: 15 February 2026