Formulations containing two or more than two herbs are called polyherbal formulation. Drug formulation in Ayurveda is based on two principles: Use as a single drug and use of more than one drug. The latter is known as polyherbal formulation. The concept of polyherbalism is peculiar to Ayurveda although it is difficult to explain in term of modern parameters. Historically, the Ayurvedic literature “Sarangdhar samhita” highlights the concept of synergism behind polyherbal formulations. Even though single herb formulation have been well established due to their active phytoconstituents, they usually present in minute amount and sometimes they are insufficient to achieve the desirable therapeutic effects.
Scientific studies have revealed that these plants of varying potency when combined may theoretically produce a greater result, as compared to individual use of the plant and also the sum of their individual effect, thus positive herb-herb interaction produce synergism, which could be pharmacokinetic synergism or pharmacodynamics synergism. Popularity of polyherbal formulation is due to their high effectiveness in a vast number of diseases. They have wide therapeutic range (effective at low dose and safe at high dose), fewer side effects, eco-friendly, cheaper and readily available polyherbal formulations are not always safe. As described in Charaka Samhita, Ayurvedic formulations have adverse effect when prepared or used inappropriately. The problems of polyherbal formulation occur due to sources and manufacturing process, patients, Ayurvedic practitioners, drug-herb interaction, clinical reproducibility, toxicity due to improper manufacturing and irrational prescribing of polyherbal formulation as well as law and regulations. Inspite of all these problems, popularity of polyherbal formulation is increasing and hence it demands more scientific search in this field.