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 Organization: Population Council Center for Biomedical Research Phase of Development: Phase III (discontinued as a single-drug microbicide)

(Compound details obtained from ChemIDplus Advanced,1 NIAID Therapeutics Database,2 and Journal of Pharmaceutics article3)

NOTE: The development of carrageenan for HIV treatment has been discontinued.

The study of carrageenan as a single-drug microbicide for preventing HIV infection was discontinued. Data from a Phase III study demonstrated that carrageenan vaginal gel was ineffective in protecting women against sexually acquired HIV infection.3,4


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 gp120.6,7 

Clinical Trials

Study Identifiers: NCT00213083
Phase: III
Study Purpose: Study to evaluate the safety and effectiveness of carrageenan vaginal gel for the prevention of HIV infection in women
Study Population: HIV-uninfected women in South Africa
Dosing: Carrageenan gel versus placebo gel, both applied intravaginally 1 hour before vaginal intercourse. Participants used study gels for up to 2 years.4,8-11
(See references cited above for information on study results.)

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 women (2%) 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 women (2%) in the carrageenan gel group and in 78 women (3%) 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. Available at: http://chem.sis.nlm.nih.gov/chemidplus/rn/9000-07-1. Last accessed on May 6, 2015.
  2. National Institute of Allergy and Infectious Diseases (NIAID). NIAID ChemDB, HIV Drugs in Development. Available at: http://chemdb.niaid.nih.gov/DrugDevelopmentHIV.aspx. Last accessed on May 6, 2015.
  3. Singh O, Garg T, Rath G, Goyal AK. Microbicides for the Treatment of Sexually Transmitted HIV Infections. J Pharm. 2014 Feb 12;2014 doi:10.1155/2014/352425. Available at: http://www.hindawi.com/journals/jphar/2014/352425/. Last accessed on May 6, 2015.
  4. 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. Available at: http://www.ncbi.nlm.nih.gov/pubmed/19059048. Last accessed on May 6, 2015.
  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. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2983477/. Last accessed on May 6, 2015.
  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. Available at: http://www.jleukbio.org/content/80/5/1076.long. Last accessed on May 6, 2015.
  7. 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. Available at: http://www.ncbi.nlm.nih.gov/pubmed/21439325. Last accessed on May 6, 2015.
  8. The Population Council, Inc.: Press Release, dated February 18, 2008. Trial Shows Anti-HIV Microbicide Is Safe, but Does Not Prove It Effective. Available at: http://www.popcouncil.org/news/trial-shows-anti-hiv-microbicide-is-safe-but-does-not-prove-it-effective. Last accessed on May 6, 2015.
  9. Population Council. Phase 3 Study of the Efficacy and Safety of the Microbicide Carraguard® in Preventing HIV Seroconversion in Women. In: ClinicalTrials.gov. Bethesda (MD): National Library of Medicine (US). Registered on September 13, 2005. NLM Identifier: NCT00213083. Available at:  https://www.clinicaltrials.gov/ct2/show/NCT00213083. Last accessed on May 6, 2015.
  10. 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. Available at: http://www.popcouncil.org/uploads/pdfs/MIC_Phase%203%20Protocol%20Summary_Final_2_6_08.pdf. Last accessed on May 6, 2015.
  11. Marais D, Gawarecki D, Allan B, et al. The effectiveness of Carraguard, a vaginal microbicide, in protecting women against high-risk human papillomavirus infection. Antivir Ther. 2011;16(8):1219-26. Available at: http://www.intmedpress.com/serveFile.cfm?sUID=f9170522-1145-4fd4-94fe-99099cc9d23d . Last accessed on May 6, 2015.

Last Reviewed: May 6, 2015