Dragon's Blood: Crofelemer, From Sap to Licensed Drug

Table of Contents

1. What Crofelemer Is
2. Why HIV-Associated Diarrhoea
3. Two Chloride Channels
4. The ADVENT Trial
5. The 2012 US Approval
6. Other Diarrhoeas: IBS and Chemotherapy
7. Safety and Absorption
8. A Drug Made From a Variable Natural Source
9. Why the Sap Is Not the Drug
10. Key Research Papers
11. Connections

What Crofelemer Is

Crofelemer is a botanical drug substance: a medicine whose active ingredient is a purified plant-derived mixture rather than a single synthetic molecule. Chemically it is an oligomeric proanthocyanidin, meaning a mixture of short-to-medium chains built from flavan-3-ol units, the same chemical family that gives grape seeds, pine bark and many barks their astringency.

A 2013 review in Drugs described its source as the stem-bark latex of the Croton lechleri tree. Another 2013 review noted that it is manufactured from the red latex sap of the tree in South America. A laboratory paper from 2010 called it a purified proanthocyanidin oligomer extracted from the bark latex.

Proanthocyanidins make up the bulk of the latex. A 2025 review of the plant's chemistry identified them as the most abundant constituent group. So crofelemer is not an obscure trace compound; it is a cleaned-up version of the sap's main ingredient, with the other components, including the alkaloid taspine, left behind.

A 2013 review in Drugs of Today called it a "first-in-class" antidiarrhoeal: the first drug to work by its particular mechanism.

Why HIV-Associated Diarrhoea

Modern antiretroviral therapy has transformed the outlook for people living with HIV, but diarrhoea remains common. Several reviews in our citation pack explain why that matters:

• A 2016 review in Current Opinion in Infectious Diseases reported that diarrhoea is still common in HIV-positive people despite effective treatment, and that it is associated with reduced quality of life and survival. It noted that every class of antiretroviral drug can cause diarrhoea, that this is an under-recognised reason people struggle to keep taking their medication, and that the symptoms are under-reported.
• A 2013 review in HIV/AIDS (Auckland) pointed out that diarrhoea caused by some antiretrovirals can become a barrier to adherence and so affect treatment outcomes and future options.
• A 2013 review in Expert Review of Gastroenterology & Hepatology noted that with effective therapy, gut opportunistic infections have declined, while diarrhoea caused by the drugs themselves and by HIV's direct effect on the gut lining (HIV enteropathy) remains common.

Much of this diarrhoea is secretory: the gut lining actively pumps chloride into the bowel, and water follows. That is exactly the process crofelemer interrupts. The 2016 review also stressed that diarrhoea in people with HIV may have a treatable infectious cause, or a remediable non-infectious one such as pancreatic dysfunction, so the approved use is specifically for diarrhoea in which infection has been ruled out.

Two Chloride Channels

The clearest account of how crofelemer works comes from a 2010 study at the University of California, San Francisco, published in Molecular Pharmacology. Using cell lines designed to isolate one transport protein at a time, the researchers found:

• At 50 µM, crofelemer had little or no effect on sodium or potassium channels, or on the cell's internal signals (cAMP and calcium).
• It inhibited the CFTR chloride channel (the cystic fibrosis transmembrane conductance regulator, the channel that is faulty in cystic fibrosis) with a maximum inhibition of about 60% and a half-maximal concentration of about 7 µM. It acted on the outside of the channel and held it in its closed state.
• The effect was long-lasting: less than half of the CFTR block reversed four hours after washing the drug away.
• It also strongly inhibited TMEM16A, the gut's calcium-activated chloride channel, with maximum inhibition above 90% and a half-maximal concentration of about 6.5 µM.

The authors concluded that this dual action on two structurally unrelated channels may account for crofelemer's antisecretory effect. The reviews describe the same mechanism in plainer terms: blocking chloride secretion reduces the flow of sodium and water into the bowel, which reduces how often stools come and how watery they are.

The mechanism also explains why the drug does not need to be absorbed. The channels sit on the surface of the gut lining facing the bowel contents, so a molecule that stays inside the gut can reach them.

The ADVENT Trial

Approval rested mainly on ADVENT, a randomised, double-blind, placebo-controlled phase 3 trial published in HIV Clinical Trials in 2013. Its design was unusual:

• Stage I: 196 HIV-positive people with chronic diarrhoea, on stable antiretroviral therapy, were randomised to crofelemer 125 mg, 250 mg or 500 mg, or placebo, twice daily. A pre-planned analysis picked 125 mg twice daily as the dose to carry forward.
• Stage II: 180 new participants were randomised to 125 mg twice daily or placebo.
• Each stage had a 2-week screening period, a 4-week placebo-controlled treatment phase and a 20-week placebo-free extension in which everyone could take the drug.

The main outcome was "clinical response", defined as two or fewer watery stools a week during at least two of the four weeks. Results:

• 17.6% of people on crofelemer 125 mg met the definition, against 8.0% on placebo (one-sided P = .01).
• Crofelemer produced a greater reduction in daily watery bowel movements (P = .04) and a better daily stool consistency score (P = .02) than placebo.
• In the placebo-free extension, the weekly proportion of responders ranged from 40% to 56% between weeks 11 and 24. Because there was no placebo group by then, those figures cannot separate the drug's effect from natural improvement or expectation.
• The drug was minimally absorbed, did not worsen immune measures, and had a safety profile comparable to placebo.

Put simply, roughly one person in six on the drug reached the response threshold during the controlled phase, compared with about one in twelve on placebo. That is a statistically significant benefit, but most participants in both groups did not reach the threshold within four weeks.

The 2012 US Approval

The FDA approved crofelemer in December 2012, according to the 2013 Drugs of Today review. The approved use, as several reviews state it, is the symptomatic relief of non-infectious diarrhoea in adult patients with HIV/AIDS on antiretroviral therapy.

The 2013 review in Drugs described crofelemer as the first, and at that time the only, agent approved by the FDA specifically for that indication. It summarised the evidence:

• ADVENT randomised 376 patients in total across both stages.
• The dose studied for approval was 125 mg by mouth twice daily.
• The drug was generally well tolerated in ADVENT and in a separate 48-week open-label phase 3 safety study.
• Infections and gastrointestinal disorders were the most frequently reported adverse events in people taking the drug, and overall adverse-event rates were similar to placebo during the controlled phase.
• Treatment had no appreciable effect on HIV viral load or CD4 cell counts, an important point for a drug taken alongside HIV therapy.

Later reviews, including one in Expert Review of Clinical Pharmacology in 2015, describe it as a newly approved medication with a novel mechanism. Strategies for HIV-associated diarrhoea, that review notes, include switching to a different antiretroviral regimen and using specific medicines to control symptoms.

Other Diarrhoeas: IBS and Chemotherapy

Crofelemer was tested in other conditions with mixed results. A 2013 review notes that it was investigated in diarrhoea of various infectious causes, including cholera-related and acute infectious diarrhoea. Two trials in our citation pack report their full numbers.

Diarrhoea-predominant irritable bowel syndrome: negative

A double-blind, randomised, placebo-controlled trial published in Digestion in 2008 gave 242 people with diarrhoea-predominant IBS crofelemer 125, 250 or 500 mg or placebo twice daily for 12 weeks. Crofelemer did not significantly improve stool consistency (the primary endpoint), stool frequency, urgency or adequate relief. In a secondary analysis, women taking 500 mg had more days free of abdominal pain and discomfort (26.1% versus 10.6% of days in month 3); no benefit was seen in men. The authors concluded that crofelemer did not benefit bowel function and suggested studying it as a possible pain reliever for the gut instead. A finding in one subgroup of a trial that missed its main goal is a lead to test, not a result.

Chemotherapy-induced diarrhoea: primary endpoint missed

The HALT-D trial, a randomised, open-label phase 2 study published in 2022, enrolled 51 people with HER2-positive breast cancer receiving trastuzumab, pertuzumab and a taxane. Twenty-six took crofelemer 125 mg twice daily during the first two chemotherapy cycles; 25 received no scheduled preventive medicine. Everyone had standard rescue antidiarrhoeals available.

• There was no statistically significant difference in the primary endpoint, diarrhoea of any grade lasting two or more consecutive days.
• Diarrhoea of grade 2 or worse was less common with crofelemer: 19.2% versus 24.0% in cycle 1, and 8.0% versus 39.1% in cycle 2.
• People on crofelemer were 1.8 times more likely to see their diarrhoea resolve and had less frequent watery diarrhoea.

The authors argued that their primary endpoint was insensitive and called for further testing. The study was small and not blinded, so its secondary results are suggestive at best.

Safety and Absorption

Crofelemer's safety profile rests on one property more than any other: very little of it gets into the body. Reviews variously describe it as "not absorbed", "not systemically absorbed" or as undergoing "minimal systemic absorption", acting locally in the gut.

• Tolerability. In ADVENT, its safety profile was comparable to placebo. Reviews describe minimal adverse events in clinical trials.
• Liver. The US National Library of Medicine's LiverTox database states that crofelemer is associated with occasional serum enzyme elevations during therapy but has not been linked to cases of clinically apparent acute liver injury.
• Immune measures. No appreciable effect on HIV viral load or CD4 counts.
• Long-term data. The 2013 Drugs of Today review noted that long-term safety data were lacking at the time.

This record is for the purified drug at the studied dose. It says nothing direct about the crude latex, which carries taspine and other compounds that were removed in making the drug.

A Drug Made From a Variable Natural Source

Crofelemer is a mixture of many related molecules, and its natural raw material varies. A 2017 study in the Journal of Pharmaceutical Sciences, by University of Kansas researchers with an author from the FDA's Center for Drug Evaluation and Research, used crofelemer as a model for how regulators might compare complex mixture drugs from different sources.

The team extracted the drug substance from tablets of one commercial lot, fractionated it, and heated portions to produce deliberately altered lots. Chromatography, mass spectrometry and nuclear magnetic resonance revealed substantial changes in composition. Yet a cell-based test of chloride-channel inhibition suggested those changes did not necessarily cause major changes in activity. The authors noted that crofelemer lots may show significant physical and chemical variation because of their natural source.

This variability is also relevant to the crude sap. A 2002 survey across 22 sites in Peru and Ecuador found three chemical types of the tree and measured taspine at an average of 9% of the latex's dry weight. A 2003 review pointed out that sap from one area differs from another and that clinical materials would need standardising. If a purified, controlled drug still varies between lots, an unstandardised bottle of sap can be expected to vary more.

Why the Sap Is Not the Drug

An approved drug from a tree can easily be read as proof that the tree's sap works. For dragon's blood the research supports a narrower conclusion:

1. Different substance. The drug is a purified proanthocyanidin. The latex also contains taspine, an alkaloid toxic to cells in laboratory tests, plus diterpenoids, sterols, saponins and other compounds.
2. Different safety data. The drug went through controlled trials with adverse-event monitoring. The latex has tested mutagenic in bacterial and yeast assays, and there is no published human safety study of it.
3. Different dose. The trials used a measured 125 mg of purified drug twice daily. There is no established conversion between drops of sap and milligrams of crofelemer.
4. Narrow indication. The approval covers non-infectious diarrhoea in adults with HIV on antiretroviral therapy. The drug did not meet its main goal in IBS and missed its primary endpoint in a chemotherapy trial.

The traditional use of the sap for diarrhoea pointed researchers toward a real mechanism, and the drug is the tested result. Whether the crude latex itself is effective and safe for diarrhoea is a separate question that no trial in our citation pack answers. Persistent diarrhoea, particularly in someone living with HIV, can have treatable infectious causes, and the 2016 review urges clinicians to ask about diarrhoea for exactly that reason.

Key Research Papers

1. Tradtrantip L, Namkung W, Verkman AS. Crofelemer, an antisecretory antidiarrheal proanthocyanidin oligomer extracted from Croton lechleri, targets two distinct intestinal chloride channels. Molecular pharmacology. 2010;77(1):69-78. PubMed PMID: 19808995
2. Macarthur RD, Hawkins TN, Brown SJ, et al. Efficacy and safety of crofelemer for noninfectious diarrhea in HIV-seropositive individuals (ADVENT trial): a randomized, double-blind, placebo-controlled, two-stage study. HIV clinical trials. 2013;14(6):261-73. PubMed PMID: 24334179
3. Frampton JE. Crofelemer: a review of its use in the management of non-infectious diarrhoea in adult patients with HIV/AIDS on antiretroviral therapy. Drugs. 2013;73(10):1121-9. PubMed PMID: 23807722
4. Yeo QM, Crutchley R, Cottreau J, et al. Crofelemer, a novel antisecretory agent approved for the treatment of HIV-associated diarrhea. Drugs of today (Barcelona, Spain : 1998). 2013;49(4):239-52. PubMed PMID: 23616951
5. Patel TS, Crutchley RD, Tucker AM, et al. Crofelemer for the treatment of chronic diarrhea in patients living with HIV/AIDS. HIV/AIDS (Auckland, N.Z.). 2013;5:153-62. PubMed PMID: 23888120
6. Chordia P, MacArthur RD. Crofelemer, a novel agent for treatment of non-infectious diarrhea in HIV-infected persons. Expert review of gastroenterology & hepatology. 2013;7(7):591-600. PubMed PMID: 24070150
7. Castro JG, Chin-Beckford N. Crofelemer for the symptomatic relief of non-infectious diarrhea in adult patients with HIV/AIDS on anti-retroviral therapy. Expert review of clinical pharmacology. 2015;8(6):683-90. PubMed PMID: 26517110
8. Logan C, Beadsworth MB, Beeching NJ. HIV and diarrhoea: what is new? Current opinion in infectious diseases. 2016;29(5):486-94. PubMed PMID: 27472290
9. Mangel AW, Chaturvedi P. Evaluation of crofelemer in the treatment of diarrhea-predominant irritable bowel syndrome patients. Digestion. 2008;78(4):180-6. PubMed PMID: 19092244
10. Pohlmann PR, Graham D, Wu T, et al. HALT-D: a randomized open-label phase II study of crofelemer for the prevention of chemotherapy-induced diarrhea in patients with HER2-positive breast cancer receiving trastuzumab, pertuzumab, and a taxane. Breast cancer research and treatment. 2022;196(3):571-581. PubMed PMID: 36280642
11. Kleindl PA, Xiong J, Hewarathna A, et al. The Botanical Drug Substance Crofelemer as a Model System for Comparative Characterization of Complex Mixture Drugs. Journal of pharmaceutical sciences. 2017;106(11):3242-3256. PubMed PMID: 28743606
12. Crofelemer. 2012;. PubMed PMID: 31643647
13. de Albuquerque RDDG, León-Vargas FR, Carrasco-Montañez DD, et al. A Review on Phytochemistry and Recent Pharmacology of Dragon's Blood (Croton lechleri), a Multifunctional Ethnomedicinal Resource from the Amazon Forest. Planta medica. 2025;91(8):409-418. PubMed PMID: 40043740
14. Milanowski DJ, Winter RE, Elvin-Lewis MP, et al. Geographic distribution of three alkaloid chemotypes of Croton lechleri. Journal of natural products. 2002;65(6):814-9. PubMed PMID: 12088421

PubMed Topic Searches

1. PubMed: Crofelemer (all studies)
2. PubMed: Crofelemer and HIV diarrhoea
3. PubMed: Crofelemer chloride channels
4. PubMed: Crofelemer and chemotherapy-induced diarrhoea

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Connections

• All Herbs
• Dragon's Blood (Croton lechleri) — the main topic page
• Dragon's Blood: Benefits Deep Dive — the evidence ledger
• Wound Healing and Insect Bites — the traditional skin uses
• Four Plants, One Name — which resin is which
• Taspine, Toxicity and Safety Unknowns — what the drug left behind
• HIV/AIDS — the condition behind the approval
• Chronic Diarrhea — causes and evaluation
• Irritable Bowel Syndrome — the negative trial
• Cystic Fibrosis — the disease of the CFTR channel
• Cholera — the classic secretory diarrhoea
• Breast Cancer — the setting of the HALT-D trial
• Grape Seed Extract — proanthocyanidins from another plant

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