A Technological Excipient, Not an Active Ingredient
Povidone, or polyvinylpyrrolidone (PVP), is a versatile pharmaceutical excipient. Unlike an active ingredient, it has no therapeutic effect of its own: its role is to shape the medicine.
It binds powders together to form tablets, contributes to coating, and improves the dissolution of certain active substances. "Kollidon" is simply the trade name registered by BASF under which its various grades are sold.
Origin and Discovery
Povidone is a synthetic polymer, so it is not extracted from a natural source. It was developed by chemist Walter Reppe at BASF in the 1930s.
Its first notable use was medical: it served as a blood plasma substitute during the Second World War. Its binding and film-forming properties later made it one of the most widely used excipients in the pharmaceutical industry.
Structure and Manufacture: the Logic of K-Values
Povidone is obtained by polymerizing the monomer N-vinylpyrrolidone: long chains form as this unit repeats.
It comes in several grades characterized by their "K-value" (K12, K25, K30, K90…), which reflects chain length and therefore molecular weight: the higher the K-value, the "longer" and more viscous the polymer is in solution. It should not be confused with crospovidone (cross-linked povidone), which is insoluble and used as a disintegrant.
Technological Properties, Not Pharmacological Ones
Povidone has no pharmacological "mechanism of action": its functions are technological. Its key properties are:
- high solubility in water (and in many solvents);
- a binding and adhesive power that ensures the cohesion of granules and tablets;
- film-forming properties;
- the ability to complex with, and keep in solution, poorly soluble substances.
Pharmaceutical Uses of Povidone
The main uses of povidone are:
- binding agent in tablets and granules (wet granulation);
- coating agent and film former;
- improving the dissolution and bioavailability of poorly soluble active substances (solid dispersions);
- suspending and stabilizing agent in liquid dosage forms;
- additional uses: povidone-iodine is a well-known antiseptic; PVP is also used in cosmetics and as a food additive (E1201).