Oral diseases, such as periodontal disease and dental caries, are a health burden to about 3.5 billion people in the world. ¹ If untreated, there is a likelihood of complete loss of primary or permanent teeth. ² Bacteria, such as Streptococcus mutans and Lactobacillus, which convert sugars in food residues into acids, are responsible for dental caries. The production and accumulation of these acids may lead to the dematerialization of hard tooth structures, such as enamel, dentine, and cementum. Moreover, some bacteria, including Porphyromonas gingivalis and Treponema denticola, are responsible for periodontal disease associated with inflammatory responses leading to gum detachment. ³

Several antiplaque agents are commercially available, mainly as mouth rinses and gargles, to prevent and treat dental caries and periodontal diseases. ^{4 , 5} These agents include halogens, surfactants, essential oils, metal salts, phenols, plant extracts, oxygenating agents, alcohols, and enzymes. ⁶

Povidone-iodine (halogen) and chlorhexidine (surfactant) are the most common antiplaque agents in the Kenyan market, formulated as mouth rinses/mouthwashes and gargles. Povidone-iodine (halogen) is a polymer complex of polyvinyl pyrrolidone and ionic triiodide, designed for slow-release iodine, an active entity. ⁷ Iodine causes the oxidation of biomolecules leading to disruption of microbial metabolic pathways and cell membranes integrity, which results in cell death. ⁷ Structurally, chlorhexidine is made up of biguanide groups and 4-chlorophenyl rings, which are linked via a hexamethylene chain. ⁸ Chlorhexidine digluconate is a stable salt, which has a high affinity for anionic elements, thus exerting microbial death by inhibiting glycosidic and proteolytic enzymes. ⁸

For successful prevention and treatment of plaques, the quality of the mouth rinse or gargle is essential. Quality products are effective and pathogen-free. ^{9 , 10} On the contrary, substandard products are associated with economic losses, especially for patients. Other detrimental effects include product recalls, treatment failure, and loss of confidence in the product and health care systems. ¹¹ Adherence to current Good Manufacturing Practices (cGMP) guidelines and labeling requirements as prescribed by the relevant regulatory bodies assures the quality of the products. In Kenya, oral hygiene products, namely mouthwashes, are regulated by the Kenya Bureau of Standards (KEBS). ¹² The quality specifications are prescribed in the standard KS ISO 160408:2015. The regulation of health products in Kenya is vested on the Pharmacy and Poisons Board (PPB). ¹³ Therefore, manufacturers of oral care products must comply with regulations from either of the two regulatory authorities that may be considered easy to meet at a minimal cost.

Information on the quality of antiplaque products in the Kenyan market is unavailable. To the best of our knowledge, the present study is the first report on the quality of antiplaque products in Kenya.

The results obtained for the labeling requirements are presented in Table 1 while the assay results are summarized in Table 2. ^{16 , 17} Labeling of the samples was qualitatively evaluated for the presence of labeling parameters that impact product identification and proper use. Missing information was common among the batches of the concerned product.

All the samples in the present study had manufacturing and expiry dates, batch numbers, brand names and the assay indicated on the labels. Additionally, all the samples were accompanied by patient information leaflets (package inserts). However, about 20% of the brands of povidone-iodine and 44% chlorhexidine products ( Table 1) did not have their storage conditions indicated on their label. Only one povidone-iodine brand (PI-13) lacked the indication of the product on the label, while three brands (PI-01, PI-02, and PI-14) lacked the details of the manufacturers’ address. Moreover, KEBS S-marks were absent in all povidone-iodine products and 77% of chlorhexidine-based products.

Guidelines set by the Pharmacy and Poisons in Kenya and cGMP requirements dictate that pharmaceutical products should be clearly labeled with the product’s brand name, the name and address of the manufacturer, and the quantity/percentage of the API. Other details required include the directions of use, the storage conditions, batch number, indication and any relevant cautions. ¹³ For local distribution, products manufactured in Kenya should have label information in English or Kiswahili. By contrast, the label is written in the original language for imports, and a complete translation should be provided. ¹³

In the present study, all the samples had manufacturing, expiry dates, batch numbers, brand names, and the assay indicated on the labels. Additionally, all the samples were accompanied by patient information leaflets (package inserts). However, about 20% of the brands of povidone-iodine and 44% chlorhexidine products ( Table 1) did not have their storage conditions indicated on their label. Only one povidone-iodine brand (PI-13) lacked the indication of the product on the label. Three brands (PI-01, PI-02, and PI-14) lacked details on the address of the respective manufacturers. The KEBS S-mark was absent in both povidone-iodine (100%) and chlorhexidine-based products (77%). According to a study conducted by Nyamweya and Abuga in Nairobi county to check for the compliance of hand sanitizers to packaging, labeling, and regulatory standards, products lacking the KEBS S-mark were regarded as either counterfeit or substandard. ¹⁹

The strength of povidone-iodine is dependent on the concentration of unbound iodine in the complex. ^{20 , 21} The assay results for povidone-iodine products revealed that 52.9% of samples representing six brands failed to comply with assay specifications within the 24-84% label claim range. Due to low iodine content, these non-compliant samples may be ineffective as gargles and mouth rinses. The findings from this study corroborate those reported for Tucuman, Argentina ²² whereby 50% of the collected samples complied with specifications. ²² However, a similar study in Iraq reported that many of the samples of povidone-iodine and chlorhexidine mouthwashes/gargles did not comply with assay specifications. ²³

Products with an iodine content above the pharmacopoeia limit, e.g., PI-13, may lead to allergic or primary irritant dermatitis. ¹⁸ In addition, iodine absorption via the oral transmucosal route may interfere with serum thyroid-stimulating hormone levels and, in turn, affect thyroid gland function. In the case of chlorhexidine-based products, four samples (33.3%) failed to comply with the assay specifications. These samples had chlorhexidine assay values below the lower pharmacopeial limit compromising their antimicrobial efficacy.

This study evaluated the quality of chlorhexidine and povidone-iodine-based mouth gargle/rinse products for the BP (2017) assay specifications and regulatory requirements for labelling in Nairobi County. From the non-compliance rates recorded, a wide range of problems of the antiseptics is anticipated. Poor-quality products undermine their application in controlling the spread of infections for households and healthcare systems. Similarly, poor-quality products may lead to a wastage of the consumers’ financial resources, and also cause a lack of trust in the regulatory authorities. Regulatory agencies, such as the PPB and the Kenya Bureau of Standards, should institute the requisite regulations to rid the market of sub-standard and falsified products to protect the unsuspecting public. Regulatory stringency is critical at all levels of the product life cycle from the manufacture, registration, distribution, and use. For this purpose, the regulators and manufacturers are responsible for ensuring adherence to cGMP, quality, safety, and efficacy of medicinal products. Continuous post-market surveillance could be instrumental in ensuring products in circulation are quality assured, hence conferring users’ confidence. Further investigations are needed to determine the quality of chlorhexidine and povidone-iodine-based oral products in other parts of Kenya.