Andrographis paniculata is a bitter herb from the Acanthaceae family that is native to South Asian countries and has been used in traditional Ayurvedic and Chinese medicine for over 2,000 years. Known as “King of Bitters” in India, it has one of the most potent antiviral and immunomodulatory profiles of any plant compound studied to date — with demonstrated activity against herpes simplex virus, influenza, dengue fever, chikungunya, and SARS-CoV-2. It is also one of the most extensively studied herbs for the reduction of respiratory infection severity and duration.
The Andrographolide Mechanism
The primary active compounds in andrographis are the andrographolides — a group of diterpenoid lactones. The most important of these is the inhibition of NF-kB — the master transcription factor for inflammatory gene expression. By inhibiting NF-kB, andrographolide reduces the production of cytokines (TNF-alpha, IL-6, IL-1beta) that drive the cytokine response to viral infection. This matters because the severe outcomes in viral respiratory infections are driven not by the virus itself but by the dysregulated cytokine response. Additionally, andrographolides stimulate the production of antibodies by B lymphocytes, increase the activity of natural killer (NK) cells and macrophages, and enhance the production of interferon-gamma (IFN-gamma).
Evidence for Respiratory Infection
The most consistent clinical evidence for andrographis is in the treatment and prevention of upper respiratory tract infections (URTIs). A meta-analysis of 7 RCTs in 787 patients with influenza-like illness found that andrographis at 120-300mg daily of standardised extract significantly reduced the severity of symptoms compared to placebo, with effects comparable to oseltamivir (Tamiflu) in some studies for influenza specifically. For prevention, a double-blind RCT in 223 healthy adults during flu season found that andrographis at 200mg daily reduced the incidence of URTI by 50% compared to placebo over 3 months.
Andrographis and COVID-19
The connection between andrographis and COVID-19 emerged from early in vitro studies showing that andrographolide inhibited SARS-CoV-2 replication in cell culture. Subsequent studies confirmed the binding of andrographolide to the spike protein and main protease of SARS-CoV-2. A small open-label RCT in hospitalised COVID-19 patients in Thailand found that andrographis at 180mg daily reduced the time to clinical recovery by approximately 3 days compared to standard care alone. This preliminary evidence has led to andrographis being included in the Thai national guidelines for COVID-19 management.
Practical Dosing and Quality
The evidence-based dose for immune support and respiratory infection prevention is 200-400mg of standardised andrographis extract (minimum 30% andrographolides) daily. For acute infection, higher doses of 300-600mg daily in divided doses are used for the first 5-7 days. Andrographis is generally well-tolerated but can cause GI discomfort due to its bitter properties. It should not be used in pregnancy (it has uterine-stimulating properties) or in people with autoimmune conditions.
What the Research Actually Shows
Nutritional science in this area has advanced significantly over the past decade, with larger-scale randomised controlled trials replacing the small observational studies that dominated earlier literature. The best-designed studies in this field now use objective biomarkers rather than subjective self-reports, and the consensus emerging from this more rigorous research is that the compound in question has meaningful physiological effects at appropriate doses — but that bioavailability, formulation quality, and individual variation in absorption substantially affect outcomes in practice. Not all supplements are created equal, and the gap between research-grade and commercial formulations can be significant.
Mechanism of Action
This compound works through multiple intersecting biochemical pathways. The primary mechanism involves modulation of the gut-brain axis — a bidirectional communication network linking intestinal permeability, microbial composition, and neurological inflammation. By influencing gut barrier integrity and microbial metabolites, it affects systemic inflammation levels that in turn influence brain function. A secondary mechanism involves direct activity at neurotransmitter systems or cellular metabolism pathways, providing a multi-target profile that is characteristic of many effective nutritional interventions.
Key Practical Considerations
Dosage and formulation are the two most important practical variables. Most research uses doses that are difficult to achieve through standard dietary intake, meaning that supplementation is typically necessary for therapeutic effects. The form matters substantially — some compounds have poor bioavailability in certain formulations, and the difference between a highly absorbable form and a poorly absorbed form can be a tenfold difference in blood levels at equivalent doses. Working with a knowledgeable practitioner to guide supplementation is the most reliable way to ensure appropriate dosing.
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