What is Astodrimer Sodium? Understanding this Dendrimer-Based Microbicide

October 6, 2025 •

3 min read

In a clinical study published in 2022, a 1% astodrimer sodium nasal spray was well-tolerated in healthy adult volunteers and showed no systemic absorption, confirming its potential as a safe topical microbicide. So, what is astodrimer sodium? It is a unique, negatively-charged dendrimer molecule that combats infections by forming a physical barrier against pathogens.

Quick Summary

Astodrimer sodium is a polyanionic dendrimer that inhibits infections by preventing pathogens from attaching to host cells and disrupting bacterial biofilms. Used topically in gels and nasal sprays, it addresses conditions like bacterial vaginosis and reduces respiratory viral loads.

Key Points

Unique Dendrimer Structure: Astodrimer sodium is a synthetic, highly-branched dendrimer with a polyanionic surface charge, crucial for microbicidal function.
Broad-Spectrum Activity: Exhibits antiviral and antibacterial properties by targeting pathogen surfaces to prevent attachment.
Biofilm Disruptor: For bacterial vaginosis, it disrupts and prevents bacterial biofilms, a cause of recurrence.
Minimal Systemic Absorption: Minimized absorption when applied topically results in a favorable safety profile.
Topical Applications: Used in vaginal gels for BV and nasal sprays for reducing respiratory viral load.
Alternative to Antibiotics: Offers a non-antibiotic option for BV, reducing resistance concerns.

The Science Behind Astodrimer Sodium

Astodrimer sodium, also known as SPL7013, is a synthetic dendrimer characterized by a highly-branched, tree-like structure. Its surface is covered with negatively charged sulfonate groups, creating a polyanionic molecule. This structure allows astodrimer sodium to bind strongly to positively charged areas on viruses and bacteria, which is key to its microbicidal activity.

Mechanism of Action

Astodrimer sodium works by physically and electrostatically interfering with pathogens:

Antiviral Barrier: It mimics heparan sulfate proteoglycans (HSPGs) on host cells that viruses like SARS-CoV-2 use to attach. By binding to the virus's surface, it blocks the virus from infecting host cells. This binding is strong and neutralizes the virus.
Antibacterial Biofilm Disruption: For bacterial vaginosis, astodrimer sodium prevents bacteria from attaching to vaginal cells and disrupts bacterial biofilms that cause resistance to treatment.

Clinical Applications of Astodrimer Sodium

Astodrimer sodium is used in topical treatments because it is not absorbed systemically.

Bacterial Vaginosis (BV) Treatment

A vaginal gel containing astodrimer sodium (VivaGel®) is approved for treating and preventing recurrent bacterial vaginosis in some countries. It offers a non-antibiotic option that avoids antibiotic resistance. Clinical trials show the gel is more effective than placebo for treating and preventing BV.

Respiratory Virus Prevention

As a 1% nasal spray (Viraleze™), astodrimer sodium forms a barrier in the nose to reduce exposure to respiratory viruses, including SARS-CoV-2. A study in COVID-19 patients found the nasal spray reduced viral load, particularly in older individuals. It serves as an additional measure alongside vaccines and other strategies.

Other Applications

Research suggests other uses for astodrimer sodium:

STI Prevention: It is used on some condoms to inactivate viruses like HIV and HSV-2.
Ocular Infections: Preclinical studies indicate potential for treating eye infections caused by adenoviruses.

Astodrimer Sodium vs. Conventional Treatments: A Comparative Look

This table compares astodrimer sodium with traditional systemic antibiotics for bacterial vaginosis.


Feature	Astodrimer Sodium Gel	Conventional Antibiotics (e.g., Metronidazole)
Mechanism of Action	Localized barrier action; disrupts bacterial biofilms.	Systemic action; kills or inhibits bacterial growth.
Systemic Absorption	Minimal to none; acts topically at the site of infection.	Significant absorption; circulates throughout the body.
Antibiotic Resistance	No potential to cause or contribute to antibiotic resistance.	Associated with a risk of resistance development.
Biofilm Activity	Disrupts and inhibits pathogenic bacterial biofilms, a key factor in recurrence.	Generally do not target or eliminate biofilms effectively.
Recurrence Rates	Clinical trials show lower recurrence rates compared to placebo.	High rates of recurrence are common after initial treatment.
Side Effects	Primarily mild and local (e.g., vaginal irritation); vulvovaginal candidiasis may occur.	Broader range of potential systemic and gastrointestinal side effects.

Safety and Tolerability Profile

Astodrimer sodium is generally well-tolerated because it is minimally absorbed systemically. Side effects are usually mild and temporary.

Potential Side Effects

Vaginal Gel: Mild local effects like itching, burning, and discharge have been reported. Some users may experience a yeast infection, similar to or less often than with other treatments.
Nasal Spray: Studies found mild and temporary side effects like headache and nasal discomfort, occurring at similar rates to placebo.

Contraindications

Do not use if you are hypersensitive to astodrimer sodium or its ingredients. Due to minimal absorption, interactions with other medications are unlikely.

Future Perspectives

Astodrimer sodium's broad-spectrum activity and unique mechanism make it a promising tool against current and future infections. Future research may explore its use in other areas or against new pathogens. Its safety and effectiveness in treating common and recurrent infections make it a valuable medical option.

Conclusion

Astodrimer sodium is a polyanionic dendrimer topical microbicide that creates an electrostatic barrier and disrupts biofilms. It treats bacterial vaginosis and prevents respiratory viral infections, offering a safe and effective option with minimal systemic absorption. More information on astodrimer sodium nasal spray safety is available on {Link: PMC NCBI https://pmc.ncbi.nlm.nih.gov/articles/PMC9204674/}.

Frequently Asked Questions

Astodrimer sodium is also known by its code, SPL7013.

It functions as a physical barrier by electrostatically binding to positively charged regions on the surface of viruses, like the spike protein of SARS-CoV-2. This action blocks the virus from attaching to and entering host cells to cause infection.

No, because of its large molecular size and strong negative charge, astodrimer sodium is not systemically absorbed when applied topically to mucosal membranes, such as the vaginal or nasal passages.

Side effects are typically mild and local, including vaginal itching, burning, and discharge. In some cases, vulvovaginal candidiasis (yeast infection) may occur more frequently than with placebo.

Clinical trials for astodrimer sodium nasal spray have shown it can reduce viral burden and increase viral clearance in patients with mild to moderate COVID-19. It acts as a barrier to reduce viral exposure, complementing other prevention strategies.

Unlike traditional antibiotics that have systemic effects and risk contributing to resistance, astodrimer sodium is a topical, non-antibiotic treatment that targets and disrupts bacterial biofilms locally, which are central to BV recurrence.

Astodrimer sodium's antiviral activity relies on binding to conserved, positively charged regions on viral surfaces. This broad-spectrum approach has demonstrated activity against various strains, including different variants of SARS-CoV-2.