Microbiological stability of tablets stored under tropical conditions

doi:10.1016/0378-5173(89)90039-2

International Journal of Pharmaceutics

Volume 55, Issues 2–3, 15 October 1989, Pages 175-183

https://doi.org/10.1016/0378-5173(89)90039-2 Get rights and content

Abstract

The effect of storage under tropical conditions on the behaviour of microbial contamination of tablets was studied. The investigation of the microbiological quality of the starting materials showed that rice and tapioca starch had a higher level of natural contamination than potato starch. Lactose/potato starch tablets without preservatives, inoculated with Aspergillus niger spores, spoiled due to mould growth when stored under tropical conditions (31° C and 95% RH). Under these conditions tablets prepared with lactose and rice or tapioca starch spoiled due to growth of natural contaminants. No growth of bacterial cells (Bacillus brevis) was observed during storage under these conditions. When the tablets were stored under more moderate conditions (31° C, 75% RH) they were not at risk of microbiological spoilage. Sodium methylhydroxybenzoate and potassium sorbate were evaluated for their efficacy against microbiological spoilage of tablets. A concentration of 1% w/w of either preservative prevented growth of Aspergillus niger on lactose/potato starch tablets stored at 31° and 95% relative humidity. A 0.1% w/w concentration level of preservative was not as effective. Adding a preservative to lactose/potato starch tablets contaminated with Bacillus brevis spores did not affect the viability of these bacterial spores. The addition of preservatives to tablets prepared with lactose and rice or tapioca starch and stored under tropical conditions prevented microbiological spoilage caused by growth of natural contaminants.

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This study reports the tableting of whole fruit powder from pitaya and guava and their dissolution in relation to use as drink's tablets. Pulps of both fruits with peels and seeds were freeze-dried into powders with addition of 10% maltodextrin. The fruit powders, individually as well as in a binary mixture (1:1), were analyzed for material properties and were found to be poor in flow. Among the three powders, guava powder attained the lowest density during compaction and exhibited as a poor compressible powder. Mixed fruit tablets containing 1% effervescent agent eroded quite fast in all three types of solvents studied. However, the acidic solvent (0.1 N HCl) was found to be not suitable for erosion of tablets containing polyvinypolypyrrolidone (Kollidon CL). In terms of active ingredient release (antioxidant), Kollindon CL was found to be the best. In the case of color release (a^⁎), the faster the erosion, the better was the color intensity irrespective of dissolution media. As drink tablets, the mixture containing 10% sugar was highly preferred by majority of panelists (80%). A month long storage study with the mixed fruit tablet formulation at room temperature showed good microbial stability.
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Eighty-two spray-dried pharmaceutical plant extracts were analyzed in order to determine the profile of their microbial contamination. This profile seems to be qualitatively similar to that of the raw plant powders described in the literature. Quantitatively spray-dried extracts were less contaminated, but the total viable bacterial aerobic count remained relatively high, exceeding 10³ CFU/g in 35 samples. The most frequently identified species were Gram-positive rods (56/82). Intestinal enterobacteria (growing at 44°C) were never displayed, but enterococci and group D streptococci were identified in 20 samples, and considered as a better index of a faecal contamination. Staphylococcus aureus (1/82) and Pseudomonas aeruginosa (none) are likely contaminants for this kind of product. Moreover, in view of the low water content of the product (never exceeding 4%) the contaminating bacteria can be estimated to be in a static state. According to the observed profile of contamination, the original plant seems to be the main source of contamination of the spray-dried product. The spray drying process (including the extraction) insufficiently reduces this initial contamination. Thus efforts must be developed in order to optimize both the process and the selection, control and cleansing of the original material.
On the mechanism of kill of microbial contaminants during tablet compression
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Separate batches of three tabletting excipients, lactose monohydrate, maize starch and Avicel PH-101, were contaminated with vegetative bacteria, Staphylococcus aureus or Enterobacter cloacae. The bacteria were allowed to grow in the excipient, such that they were adhered to the surface of the powder. The contaminated powders were tabletted at various compression forces. The extent of kill was assessed for each organism and compression/kill curves were produced. The extent of kill on tablet compression was greatest for the larger organism, E. cloacae, indicating that size is important and that cell rupture by shear, rather than heat, is the mechanism of kill. The type of consolidation during compaction (plastic flow or brittle fracture) influenced survival, plastic flow causing the greatest kill at low compression forces. The results are related to published data for the kill of spores during compaction.
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International Journal of Pharmaceutics

Abstract

References (19)

Degradation mechanisms for water-soluble drugs in solid dosage forms

J. Pharm. Sci.

Inimical effects of compaction speed on microorganisms in powder systems with dissimilar compaction mechanisms

J. Pharm. Sci.

Effect of spatial distribution of contaminant microorganisms within tablet formulations on subsequent inactivation through compaction

Int. J. Pharm.

The quantitative determination of Enterobateriaceae in pharmaceutical preparations

Int. J. Pharm.

Survival of Staphylococcus aureus on pharmaceutical oral solid dosage forms

J. Pharm. Sci.

Water available to Enterobacter cloacae contaminating tablets stored at high relative humidities

J. Pharm. Pharmacol.

Preservation of solid oral dosage forms

Native starch in tablet formulations properties on compaction

Pharm. Weekbl. Sci. Ed.

Flore microbienne des médicaments données écologiques et sensibilité aux antibiotiques (Ire partie: formes magistrale sèches)

J. Pharm. Belg.

Cited by (24)

Compressibility and dissolution characteristics of mixed fruit tablets made from guava and pitaya fruit powders

Microbiological quality of spray-dried pharmaceutical plant extracts

On the mechanism of kill of microbial contaminants during tablet compression

Stability

Stability Studies of Solid Dosage Forms

Microbial Stability of Pharmaceutical and Cosmetic Products