Substances used for the preservation of microbially susceptible ointment bases. Although they are not "medicinally active ingredients", they are, according to the prevailing interpretation, "effective other ingredients" of a formulation. Therefore, in contrast to excipients, which do not have a pharmacological effect of their own or do not influence it, they should not be added without the consent of the physician if possible.
Preservatives
DefinitionThis section has been translated automatically.
Field of application/useThis section has been translated automatically.
Formulations which contain water in their external phase (oil-in-water lotions, oil-in-water creams, water-in-oil lotions, water-in-oil creams, see also creams, lotions) and are intended to be preserved over a longer period of time.
Notice!
Preparations with an alcohol content > 20% are not at risk. Formulations with a low water content (powders, oils or fatty ointments) are only susceptible to germ multiplication if the container is constantly opened.Notice! Preservatives are common contact allergens (Kathon CG by 4%, benzalkonium chloride, thiomersal and parabens by 2% each), so whenever possible, one should try to do without preservatives (recipe of small amounts, storage in the refrigerator)!
TablesThis section has been translated automatically.
Overview of the most common substances used for the preservation of externals
Preservative |
Concentration |
Use |
Benzoic acid |
0,1-0,2% |
|
Benzyl alcohol |
1-2% and above |
|
Benzalkonium chloride |
0,002-0,02% |
especially for eye, nose and ear drops |
Chlorbutanol |
0.3-0.5% (unstable at pH > 5) |
|
Chlorhexidine diacetate |
0,005-0,1% |
especially for eye, nose and ear drops |
Chlorhexidine digluconate |
0,005-0,01% |
especially for eye, nose and ear drops |
5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-iso-thiazolin-3-one, Kathon CG |
|
mainly cosmetics |
Ethanol |
> 15% |
|
Glycerol |
> 30% |
|
p-Hydroxybenzoic acid methyl ester, nipagine, solbrol |
0,06% |
|
ethyl p-hydroxybenzoate |
0,07% |
|
p-Hydroxybenzoic acid propyl ester, Nipasol, Solbrol P |
0,04% |
|
Imidazolinyl urea, Germall 115 |
|
mainly cosmetics |
Potassium sorbate |
0,1% |
|
Sodium benzoate |
0,1-0,2% |
|
Phenoxyethyl alcohol |
1-1,5% |
|
phenyl mercury compounds, such as -borate, -nitrate, -acetate |
0,002-0,005% |
especially for nose and ear drops as well as rectally and vaginally applicable external preparations |
1,2-propylene glycol |
> 15% |
|
Sorbic acid and its salts |
0.1-0.15% (unstable at pH > 5) |
|
Sorbitol |
> 70% |
|
Thiomersal |
0,002-0,015% |
especially for eye, nose and ear drops |
Preservative |
available concentration [%] |
Effectiveness against Gram-positive pathogens |
Effectiveness against Gram-negative pathogens |
Efficacy against yeasts |
Effectiveness against fungi |
Chlorbutanol |
0,5 |
very effective |
very effective |
weakly effective |
weakly effective |
Benzyl alcohol |
1,0 |
very effective |
weakly effective |
weakly effective |
weakly effective |
Phenylethyl alcohol |
1,0 |
very effective |
very effective |
weakly effective |
weakly effective |
Phenol, cresol |
0,3 |
very effective |
very effective |
weakly effective |
weakly effective |
PHB methyl ester |
1,18 |
very effective |
very effective |
not effective |
not effective |
PHB propyl ester |
0,02 |
very effective |
very effective |
weakly effective |
not effective |
PHB mixture M + P |
0,2 |
very effective |
very effective |
weakly effective |
weakly effective |
PHB mixture M + P + benzyl alcohol |
0,2 + 0,5 |
very effective |
very effective |
very effective |
very effective |
Benzoic acid |
0.1 (only in the pH 6 range) |
not effective |
not effective |
very effective |
very effective |
Sorbic acid |
0.2 (only in the pH 6 range) |
not effective |
not effective |
very effective |
very effective |
Chlorhexidine |
0,005-0,1 |
very effective |
very effective |
weakly effective |
weakly effective |
Benzalkonium chloride |
0,01 |
very effective |
weakly effective |
very effective |
very effective |
Phenylmercurinittate |
0,001 |
very effective |
very effective |
very effective |
very effective |
Thiomersal |
0,02 |
very effective |
very effective |
very effective |
very effective |
Preservative |
Optimal pH range |
||||||||
|
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
Chlorbutanol |
very effective |
very effective |
very effective |
very effective |
not effective |
not effective |
not effective |
not effective |
not effective |
Benzyl alcohol |
very effective |
very effective |
very effective |
very effective |
weakly effective |
weakly effective |
not effective |
not effective |
not effective |
Phenol, cresol, p-chloro-m-cresol |
very effective |
very effective |
very effective |
weakly effective |
weakly effective |
weakly effective |
weakly effective |
weakly effective |
weakly effective |
PHB methyl ester |
very effective |
very effective |
very effective |
very effective |
very effective |
weakly effective |
weakly effective |
weakly effective |
not effective |
PHB propyl ester |
very effective |
very effective |
very effective |
very effective |
very effective |
weakly effective |
weakly effective |
weakly effective |
not effective |
Sodium sulphite |
not effective |
not effective |
not effective |
not effective |
not effective |
very effective |
very effective |
very effective |
not effective |
Benzoic acid (pKa value 4.194) |
very effective |
very effective |
very effective |
very effective |
very effective |
not effective |
not effective |
not effective |
not effective |
Sorbic acid (pKa value 4,76) |
very effective |
very effective |
very effective |
very effective |
very effective |
not effective |
not effective |
not effective |
not effective |
Chlorhexidine |
not effective |
not effective |
not effective |
very effective |
very effective |
very effective |
very effective |
not effective |
not effective |
Benzalkonium chloride |
not effective |
very effective |
very effective |
very effective |
very effective |
very effective |
very effective |
weakly effective |
weakly effective |
Phenylmercurinitrate |
not effective |
not effective |
not effective |
not effective |
not effective |
very effective |
very effective |
very effective |
very effective |
Thiomersal |
very effective |
very effective |
very effective |
very effective |
very effective |
very effective |
not effective |
not effective |
not effective |
Phenylethyl alcohol |
very effective |
very effective |
very effective |
very effective |
very effective |
very effective |
not effective |
not effective |
not effective |