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Povidone Excipient | Uses, Suppliers, and Specifications
Povidone is a synthetic linear polymer and a pharmaceutical excipient made up of 1-vinyl-2-pyrrolidinone monomers. Depending on the degree of polymerization different polymers of various molecular weights (identified by their K values) are obtained. Povidones occur as fine, white or cream-coloured, odourless and hygroscopic powders.
Synonyms and Trade Names: Povidone; Polyvidone; Polyvinylpyrrolidone; Poly[1-(2-oxo-1-pyrrolidinyl)ethylene]; 1-Vinyl-2-Pyrrolidinone Polymer; E1201; POVIPHARM®; Kollidon® Povidone; PLASDONE™
Pharmacopoeial Conformity: USP-NF; Ph. Eur; JP; IP; FCC
Uses and Applications: Wet Granulation Binder; Suspending Agent, Viscosity-Increasing Agent, and Solubiliser
Description
Povidone, sometimes referred to as Polyvinylpyrrolidone or PVP, is a water-soluble synthetic polymeric excipient. It was initially developed as a plasma expander, and continued to be used this way over several decades. This application has now waned, but Povidone continues to be widely used in cosmetics, food products (both in processing and non-edible coatings), and in pharmaceuticals as an excipient.
Povidone, and the closely related analogues, Crospovidone and Copovidone, are some of the different products that developed out of the famed acetylene chemistry programme started and led by the chemist, Walter Reppe of BASF in the early 1930s. The method of synthesis he developed is still used today to produce Povidone, the so-called Reppe method.
The Reppe method is a multistep pathway carried out in an aqueous medium in the presence of hydrogen peroxide. Butane diol, produced following the reaction of formaldehyde and acetylene, is oxidatively cyclised to butyrolactone. The butyrolactone is reacted with ammonia to form pyrrolidone, followed by the addition of a vinyl group to produce N-vinylpyrrolidone-2. The N-vinylpyrrolidone-2 is polymerised to produce Povidone (polyvinylpyrrolidone).
By controlling the degree of polymerisation, a wide assortment of molecular weights, ranging from a few thousands to millions of Daltons, is obtained (typically 2,500–3,000,000 Da).
In pharmacopoeia, Povidone is described as a synthetic polymer made up of 1-vinyl-2-pyrrolidinone groups, with differing degrees of polymerisation which result in polymers of various molecular weights. Generally, all grades of Povidone are identified by their viscosity in aqueous solution, relative to that of water, expressed as a K – value. K-values vary between 10 and 120, and can be using Fikentscher’s equation as follows:
where z is the relative viscosity of the solution of concentration c (in % ), and k is the K – value x 10-3.
The approximate molecular weights for different pharmaceutical-grade Povidones are shown below:
| K-value | Approximate molecular weight |
| 12
15 17 25 30 60 90 120 |
2 500
8 000 10 000 30 000 50 000 400 000 1 000 000 3 000 000 |
Excipient grades are supplied as a fine, white to creamy white coloured, odourless or almost odourless, hygroscopic powder. Povidone grades with K- values equal to or lower than 30 are spray–dried and occur as spheres. Povidones with K 90 are manufactured by drum drying and occur as plates.
Chemical Structure & Identifiers
| Chemical Name | 1-Ethenyl-2-pyrrolidinone homopolymer |
| CAS Registration Number | [9003-39-8] |
| Empirical Formula | (C6H9NO)m |
| Molecular weight | 2500 – 3 000 000 |
| EINCES Number | 201-800-4 |
| UNII Code (FDA) | FZ989GH94E |
Regulatory Status
Povidone is lan approved pharmaceutical excipient and food additive. It is currently isted in all major pharmacopoeia, including the USP-NF; Ph.Eur and JP. Povidone is included in the US FDA Inactive Ingredients database for a number of dosage forms, including:
- IM and IV injections
- Ophthalmic preparations
- Oral capsules, drops, granules, suspensions and tablets
- Sublingual tablets
- Topical and virginal preparations
For food applications, Povidone is has a monograph in the Food Chemicals Codex (FCC).
Physicochemical Properties
| Physical form | Solid, powder |
| Appearance | Amorphous, white to whitish powder |
| pH value | pH = 3.0 – 7.0 (5% aqueous solution) |
| Bulk density | 0.28 – 0.42 g/cm3 |
| Tapped density | 0.39 – 0.54g/cm3 for Plasdone ® |
| True density | 1.181-1.183 g/cm3 depending on grade/supplier |
| Flowability | 20 g/s for Povidone K 15; 15g/s for Povidone K 29/32 |
| Melting point | Softens at around 150 oC |
| Moisture content | Povidone is very hygroscopic, with significant amounts of moisture being absorbed at low relative humidity. |
| Particle size distribution | Kollidon® 25/30: 90% > 50, 5% >200m; Kollidon 90:90% > 200m, 95% > 250m |
| Solubility | Freely soluble in water, acids, ethanol (95%) and IPA. Practically insoluble in mineral oil. |
| Viscosity (Brookfield) | Viscosity of aqueous povidone solutions is influenced by the concentration and the molecular weight of the polymer. Typical ranges: 1.2-2.5 mPa s (10% Povidone K12) and 3300-700 mPa s (10% Povidone K90) |
Pharmacopeoeal Specifications
| Test | USP-NF | Ph.Eur | J.P |
| Official name | Povidone | Povidone | Povidone |
| Authorised uses | Excipient | Excipient | Excipient |
| Definition | specified | specified | specified |
| Identification | A, B, C, D, E | A, B, C, D, E | A, B, C, D, E |
| Appearance | White or yellowish-white powder or flakes | White or yellowish-white powder or flakes | White or yellowish-white powder or flakes |
| Solution S1 | specified | specified | specified |
| Appearance of solution | specified | specified | specified |
| pH (5% solution)
Povidone with K-value ≤30 Povidone with K-value ≤30 |
n/a n/a0 |
3.0 – 5.0 4.0- 7.0 |
3.0 – 5.0 4.0- 7.0 |
| Aldehydes | ≤0.05% | ≤500ppm | ≤500ppm |
| Peroxides | n/a | ≤400ppm | ≤400ppm |
| Hydrazine | ≤1ppm | ≤1ppm | ≤1ppm |
| Impurity A | ≤10ppm | ≤10ppm | ≤10ppm |
| Impurity B | ≤3% | ≤3% | ≤3% |
| Heavy metals | ≤10ppm | ≤10ppm | ≤10ppm |
| Water | ≤5% | ≤5% | ≤5% |
| Sulphated ash | ≤0.1% | ≤0.1% | ≤0.1% |
| Viscosity (expressed as K-value) | n/a | n/a | specified |
| Assay (nitrogen content) | 11.5 – 12.8% | 11.5 – 12.8% | 11.5 – 12.8% |
| Labelling | specified | n/a | n/a |
Key: n/a Specification is not listed
*All claims with respect to conformity are subject to our Terms and Conditions. No express or implied warranty is made for specific properties or fitness for any particular application or purpose.
Applications in Pharmaceutical Formulations or Technology
Povidones are an important class of excipient within the pharmaceutical industry. They are currently used as:
- Binders in tablets and capsules
- Suspending agents
- Dissolution enhancers
- Matrix formers (sustained release)
- Solid dispersions or Hot melt extrusion polymers
Povidones can also be used as thickeners and viscosity-increasing agents, suspending agents and as film formers for tablets. However, while all these applications are important, the primary use is in solid dosage forms as binders in wet granulation.
How to Use Povidones in Wet Granulation
Wet granulation is still widely used especially when the active drug substance is poorly compressible, present in high or low concentration, or micronized and therefore cohesive.
In these cases, Povidone can be used as a solution (typically 10% w/v in water or hydroalcoholic solution) at levels ranging between 1-10%, depending on the grade of Povidone selected.
Alternatively, povidone can be either added directly to powder blends in the dry form and granulated in situ by the addition of water, alcohol, or hydroalcoholic solutions.
This approach requires still higher levels of Povidone, typically greater than 5% due to inefficiencies in binder mixing and sub-par granule growth.
Finally, it is also possible to blend the povidone directly with the dry formulation and the rest dissolved in water or hydroalcoholic solutions and used as the binder solution.
The last option works best where the amount of liquid needed for granulation is restricted, and therefore, using a binder solution would not produce a tacky enough binder solution to bind granules efficiently.
Which Povidone Grade To Use
Most Povidone manufacturers provide at least four or five grades of Povidone:
| K12 | K15 | K17 | K25 | K30 | K90 | |
| Appearance | White or whitish yellow, free flowing powders | |||||
| K-value | 10.5-13.5 | 12.8-17.3 | 15.3 – 18.4 | 22.5-27.0 | 27.0-32.4 | 81.0-97.2 |
| Solubility | Soluble in water, propylene glycol, ethanol and isopropanol | |||||
| Viscosity mPa s
(10% solution) |
1.3-2.0 | 1.5-2.5 | 1.5-3.7 | 3.4-8.8 | 5.5-8.5 | 300-700 |
| Particle size | Fine | Fine | Fine | Fine | Fine | Coarse |
Low molecular weight Povidones (Povidone K12, K15 and K17) produce less tacky binder solutions, and hence, suitable for formulations where compactibility and core strength are not overriding requirements, for instance, capsule formulations.
Where core strength is important, higher levels of these grades should be used, for instance, >8% w/w.
Povidone K25 and 30 represent the best balance of binder strength, tablet hardness and disintegration and therefore these grades are the most selected Povidones in actual practice. Povidone K30 is also the grade most suited for the fabrication of hot melt solid dispersions due to its greater solubilisation and carrying capacity.
Povidone K90 is suitable for high dose tablet formulations having poorly compactable ingredients for which a highly effective binder is necessitated. They are also suitable for use as matrix formers. Required levels of use as between 1-2%.
Other uses of Povidones
Povidone can be used as a solubiliser in oral and parenteral formations. It has been shown to enhance the dissolution of poorly soluble drugs forms.
Povidone solutions may also be used as coating agents or as binders when coating active pharmaceutical ingredients on a support such as sugar beads.
Povidone is additionally used as a suspending, stabilizing or viscosity–increasing agent in a number of topical and oral suspensions and solutions.
Special grades of pyrogen-free povidone are available and have been used in parenteral formulations.
Final Comments
When using Povidone as a binder, it is recommended that the material is added slowly portion-wise to the solvent with vigorous stirring to ensure complete dispersion without forming lumps.
BASF provides pyrogen-free Povidone grades (e.g Kollidon® 17 PF) for use as solublisers, crystallisation inhibitors and suspension stabilisers in injections and ophthalmic products.
Povidone K90 is a suitable alternative to Xanthan gum in oral and topical suspensions as a thickener and stabiliser. In the Japanese Pharmacopoeia, only Povidone K17PF, K25, 30 and 90 are official.
For tablets, replacing Povidone K25 or K30 with K90 can help solve the problem of weak or friable tablets without necessarily having to increase compression pressure.
Safety and Precautions
Povidone has been utilised within the pharmaceutical industry for over 70 years, having been initially developed for use as plasma expanders in the early 1930s by BASF. Even after all these many years and the introduction of other binders, Povidone remains a widely used pharmaceutical excipient, particularly in oral tablets and solutions.
When consumed orally, Povidone is essentially nontoxic since they are not absorbed from the gastrointestinal tract or mucous membranes. It has been reported to be inert and non-irritant on the skin or mucous membranes, and most importantly, to cause no sensitization. However, there are also limited reports of adverse effects when injected parenterally due to the formation of subcutaneous granulomas at the injection. There are reports that Povidone may accumulate in the body upon intramuscular injection.
A temporary acceptable daily intake for povidone has been set by the World Health Organisation at up to 25mg/kg body weight.
Toxicology: LD50 (mouse, IP): 12g/kg; Carciogencity: Not reported
Stability and Storage Conditions
All grades of Povidone intended for pharmaceutical use, with the exception of Povidone K90, are by far stable under ambient conditions and may be stored under ordinary conditions without undergoing decomposition or degradation. The minimum shelf life is 3 years, with a possible extension by 1 year. In solid dosage forms, there are no stability concerns and the material remains very stable.
Povidone K90, however, has a tendency for its K-value to decrease while at the same time the peroxide value increases (Ph.Eur limit is 400ppm). To prevent this, some manufacturers supply Povidone K90 in specially designed packaging that limits oxygen entry into the material.
Povidone, being a hygroscopic polymer, means that conditions of high humidity should be avoided. Therefore, storage in airtight containers, in a cool, dry place is recommended. Some reports show that Povidone darkens to different extents when heated, which can reduce its aqueous solubility. However, it is shown to be stable at a short cycle of heat exposure (110 – 130 °C); steam sterilization of an aqueous solution does not alter its properties. Aqueous solutions are can be attached by microbes (mould growth), and thus, the inclusion of preservatives is needed.
When handling Povidone powders, workers should observe established SHEQ protocols in-line with the quantity of material being processed. Suitable eye protection, gloves, and a dust mask are advised.
Sustainability and Environmental Impact
Povidone is an artificial polymer obtained through chemical synthesis. It is also an inert and non-toxic excipient and considered safe for the environment, with minimal long-term impact on ecology or marine life. Povidone excipient grade achieved a total score of 72/100 by the Excipients Forum Sustainable Chemistry Score™.
Manufacturers & Suppliers
BASF invented Povidone and is currently the #1 producer of povidone polymers. BASF markets Povidone under the Kollidon® brand.
- Kollidon® K12
- Kollidon® K17
- Kollidon K25
- Kollidon® 30, and
- Kollidon® 90
- Kollidon® K17 PF.
- Plasdone™ K12
- Plasdone™ K17
- Plasdone™ K25
- Plasdone™ K29/32
- Plasdone™ 90
JH Nanhang Life Sciences Co. Ltd
- Povidone K15
- Povidone K17
- Povidone K25
- Povidone K30
- Povidone K90
Additional Resources (Downloads)
References and Literature Used
[1] V. Bühler, Polyvinylpyrrolidone Excipients for Pharmaceuticals: Povidone, Crospovidone and Copovidone, Springer Science & Business Media 2005.
[2] T. Dürig, K. Karan, Binders in Wet Granulation, Editor(s): Ajit S. Narang, Sherif I.F. Badawy,Handbook of Pharmaceutical Wet Granulation, Academic Press, 2019, Pages 317-349. https://doi.org/10.1016/B978-0-12-810460-6.00010-5. (https://www.sciencedirect.com/science/article/pii/B9780128104606000105).
[3] V. Busignies, V. Mazel, H. Diarra, P. Tchoreloff, Prediction of the compressibility of complex mixtures of pharmaceutical powders, Int J Pharm, 436 (2012) 862-868. https://doi.org/10.1016/j.ijpharm.2012.06.051. Pubmed | Google Scholar
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