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Carrageenan  Audio icon

Other Names: Carraguard, PC-515, lambda carrageenan
Drug Class: Microbicides
Registry Number: 9000-07-1 (CAS)
Chemical Name: Carrageenan
Chemical Class: Natural Products, Marine Saccharides
Company: Population Council Center for Biomedical Research
Phase of Development: Phase III. In a Phase II clinical study, carrageenan vaginal gel was found to be ineffective as a topical microbicide for preventing HIV infection.

(Compound details obtained from ChemIDplus Advanced1, NIAID Therapeutics Database2, Antiviral Research article3, and The Population Council, Inc. News Release4)
Patent Version Content


Mechanism of Action: Microbicide; polyanion-based entry inhibitor. Carraguard, a sulfated anionic polymer, contains a mixture of lambda- and kappa-carrageenan derived from red seaweed.5,6 Carrageenan is broad-acting, with demonstrated activity against CXCR4 HIV isolates and other sexually transmitted pathogens.6 As a polyanionic microbicide for the prevention of sexually acquired HIV-1 infection, carrageenan’s main mechanism of action is through preventing viral attachment to target cells via electrostatic interactions with viral gp120.3,6 

Dosing in Clinical Trials

Carrageenan microbicide gel is applied intravaginally. 

Phase III (HIV-uninfected women)

  • Safety and Efficacy Study
    Carrageenan microbicide gel versus placebo gel; gels were applied within 1 hour before vaginal intercourse. (Follow-up period of up to 2 years.)4,7,8 

Additional studies of carrageenan microbicide gel have also been completed. 

Adverse Events

In the Phase III study of carrageenan microbicide gel versus placebo gel used in a coitally dependent manner for up to 2 years by over 6000 enrolled women, carrageenan gel applied vaginally was found to be safe. Ninety-five (2%) women experienced an adverse event related to gel use (48 women in the carrageenan gel group; 47 women in the placebo gel group). Serious adverse events occurred in 72 (2%) women in the carrageenan gel group and in 78 (3%) women in the placebo gel group. Only one serious adverse event, which occurred in the placebo gel group, was considered possibly related to gel use.4,8 

Drug Interactions

Drug interactions related to carrageenan microbicide gel use are currently unknown.


1. United States National Library of Medicine. ChemIDplus Advanced. Last accessed on March 13, 2014.

2. National Institute of Allergy and Infectious Diseases (NIAID). NIAID ChemDB, HIV Drugs in Development. Last accessed on March 13, 2014.

3. Pirrone V, Wigdahl B, Krebs FC. The rise and fall of polyanionic inhibitors of the human immunodeficiency virus type 1. Antiviral Res. 2011 Jun;90(3):168-82. Last accessed on March 13, 2014.

4. The Population Council, Inc.: News Release, dated February 18, 2008. Trial Shows Anti-HIV Microbicide Is Safe, but Does Not Prove It Effective. Last accessed on March 13, 2014.

5. Altini L, Blanchard K, Coetzee N, et al. Expanded safety and acceptability of the candidate vaginal microbicide Carraguard® in South Africa. Contraception. 2010 Dec;82(6):563-71. Last accessed on March 13, 2014.

6. Trapp S, Turville SG, Robbiani M. Slamming the door on unwanted guests: why preemptive strikes at the mucosa may be the best strategy against HIV. J Leukoc Biol. 2006 Nov;80(5):1076-83. Last accessed on March 13, 2014.

7. The Population Council, Inc. Phase III Study of the Efficacy and Safety of the Microbicide Carraguard in Preventing HIV Seroconversion in Women (Population Council Protocol 322): Summary. Last accessed on March 13, 2014.

8. Skoler-Karpoff S, Ramjee G, Ahmed K, et al. Efficacy of Carraguard for prevention of HIV infection in women in South Africa: a randomised, double-blind, placebo-controlled trial. Lancet. 2008 Dec 6;372(9654):1977-87. Last accessed on March 13, 2014.

Last Reviewed: March 13, 2014

Last Updated: April 25, 2014

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