Andrographis paniculata, also known as "king of bitters," has a long history of use in traditional medicine systems such as Ayurveda and Traditional Chinese Medicine for respiratory ailments, including bronchial congestion. In recent decades, there has been increasing scientific interest in its effectiveness for upper respiratory tract infections (URTIs), which often feature bronchial congestion as a symptom.

Several randomized controlled trials and systematic reviews have evaluated standardized extracts of Andrographis paniculata (often in combination with Eleutherococcus senticosus, known as Kan Jang) for acute respiratory tract infections. These studies generally report that Andrographis can reduce the severity and duration of symptoms such as cough, sore throat, and nasal congestion compared to placebo. The proposed mechanisms involve anti-inflammatory, antiviral, and immunomodulatory effects attributed to andrographolide, a principal active compound.

For example, a 2017 systematic review and meta-analysis (Cochrane Database Syst Rev. 2017 Feb 20;2:CD008416) concluded that Andrographis may be effective in relieving symptoms of uncomplicated acute respiratory tract infections, including those involving bronchial congestion. However, while results are promising, the overall methodological quality of trials varies, and larger, high-quality studies are needed to firmly establish efficacy and safety.

In summary, there is moderate scientific evidence supporting the use of Andrographis paniculata for bronchial congestion, primarily as part of broader upper respiratory tract infection symptom relief.