Pharmaceutical preparations have many ingredients those promote the microbial growth. Due to this, these non-sterile products are susceptible to the microbial growth. To prevent this microbial growth, it is required to add some antimicrobial compounds known as preservatives. These preservative does not have any harmful effect on patients consuming the products.
The key criteria for antimicrobial preservative selection are the preservative's dose, antimicrobial functionality, and effect on the active ingredient.
Additionally, the use of spectroscopic techniques (circular dichroism (CD) and fluorescence) and differential scanning calorimetry (DSC) was identified as common techniques used in evaluating an antimicrobial preservative for its impact on the conformational stability of peptide, protein, and vaccine antigens.
Phenol and benzyl alcohol are the two most common antimicrobial preservatives used in peptide and protein products while phenoxyethanol is the most frequently used preservative in vaccines.
Benzyl alcohol or a combination of methylparaben and propylparaben are generally found in small volume parenteral formulations. Their presence is mandated for multidose liquid and semi-solid products.
An effective preservative must reduce a microbial population significantly and prevent subsequent re-growth and these effects must be both microcidal and microstatic in nature.
Synergism in Preservatives
When they combined, they help to meet performance standards. Benzalkonium chloride is ineffective against some strains of Pseudomonas aeruginosa, Mycobacterium and Trichophyton but when used in combinations with EDTA, benzyl alcohol, 2-phenylethanol enhances anti-pseudomonas activity. Synergy is also observed in combination with cetrimide, 3-cresol, chlorhexidine and organo mercurials
The amino benzoic acid esters (parabens) are more active against gram-positive than gram-negative bacteria. They are more active against yeasts and molds than bacteria. Activity increases with increased alkyl chain length but on increasing alkyl chain aqueous solubility decreases, and consequently the parabens are also often used in combination.
Preservatives and their concentrations used in parental preparation
Sr. No.
|
Name
|
Recommended Concentration
|
1.
|
Benzyl Alcohol
|
0.5 to 10%
|
2.
|
Benzalkonium Chloride
|
0.01%
|
3.
|
Butyl Paraben
|
0.015%
|
4.
|
Chlorobutanol
|
0.25 to 0.5%
|
5.
|
Meta Cresol
|
0.1 to 0.25%
|
6.
|
Chlorocresol
|
0.1 to 0.18%
|
7.
|
Methyl Paraben
|
0.01 to 0.5%
|
8.
|
Phenyl Ethyl Alcohol
|
0.25 to 0.002%
|
9.
|
Propyl Paraben
|
0.005 to 0.002%
|
10.
|
Phenol
|
0.065 to 0.02%
|
Preservatives and their concentrations used in liquid oral preparation
Sr. No.
|
Name
|
Recommended Concentration
|
1.
|
Benzoic Acid
|
0.1 to 0.2%
|
2.
|
Sorbic Acid
|
0.1 to 0.2%
|
3.
|
Methyl Paraben
|
0.25%
|
4.
|
Propyl Paraben
|
0.25%
|
5.
|
Sodium Benzoate
|
0.1 to 0.2%
|
6.
|
Bronidiol
|
0.001 to 0.05%
|
7.
|
Propylene Glycol
|
0.25%
|
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