Preservative

Products

Preservatives can be found in liquid, semi-solid and solid pharmaceuticals. They are also used for food and cosmetics.

Structure and properties

Preservatives belong to various chemical groups. These include, for example:

  • Acids and their salts
  • Benzoic acid derivatives, 4-hydroxybenzoic acid derivatives.
  • Quaternary ammonium compounds
  • Alcohols
  • Phenols

Preservatives can be of natural and synthetic origin.

Effects

The antimicrobial preservatives are effective against microorganisms such as bacteria and fungi. They kill them or inhibit their growth. The various preservatives differ in their spectrum of activity. Preservatives extend the shelf life of products and prevent microbial contamination, proliferation and degradation of ingredients. Microorganisms can reduce the quality of products and cause diseases. They need water or moisture to multiply. Preservatives are especially important after the medicines have been opened. Then the container is opened and the contents can come into contact with unwanted germs. Preservatives are often only effective in a certain pH range and above a certain concentration. Therefore, the addition of acidity regulators may be necessary. Usually, they work better in the acidic to neutral range. This applies, for example, to potassium sorbate, which is effective at an acidic pH (sorbic acid). Therefore, an acid such as citric acid must be added to the preparation. Two or more preservatives are also combined for optimal effectiveness. This applies, for example, to the parabens.

Representative

Preservatives include (selection):

  • Essential oils and their components
  • Benzalkonium chloride
  • Benzoates: sodium benzoate, potassium benzoate.
  • Benzoic acid
  • Benzyl alcohol
  • Calcium lactate
  • Cetrimonium bromide
  • Cetylpyridinium chloride
  • Chelating agents such as sodium edetate
  • Chlorocresol
  • Chlorhexidine
  • Chlorobutanol
  • Vinegar
  • Acetic acid
  • Ethanol
  • Potassium disulfite
  • Copper
  • Sodium acetate
  • Sodium chloride
  • Sodium metabisulfite
  • Sodium sulfite
  • Parabens such as methyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate and propyl 4-hydroxybenzoate.
  • Phenol
  • Phenoxyethanol
  • Phenylethyl alcohol
  • Polihexanide
  • Propylene glycol
  • Sucrose
  • Acids
  • Sulfur dioxide
  • Sorbic acid
  • Sulfites
  • Thiomersal
  • Triclosan
  • Citric acid

Some of these substances are controversial and are hardly used anymore, for example mercury compounds such as thiomersal or the chlorinated triclosan. Some authors also include the antioxidants among the preservatives, so for example, butylated hydroxyanisole, butylated hydroxytoluene, sodium ascorbate, sodium metabisulfite, vitamin C and vitamin E.

Contraindications

Contraindications include hypersensitivity. For complete precautions, see the drug label.

Interactions

When formulating, it is important to note that preservatives may be incompatible with containers, active ingredients, and excipients.

Adverse effects

Preservatives have a bad reputation among consumers and are controversial. Their potential adverse effects include allergic reactions and irritation. Tolerance varies widely and depends on the substance used. If possible, they should be avoided. For example, eye drops and nasal sprays are provided with a filter that allows the drug to be marketed without preservatives.