Page 19 - Dosage 1-part2 -ebook

30/10/2025, 00:02 Pharmaceutical Solutions & Sterile Dosage Forms

Components of Solutions…. Excipients

1. pH adjusters

Buffers are employed within pharmaceutical solutions to control the pH of the formulated
product (why?)

Maintain the drug solubility in the formulation
If the drug solubility is pH-dependent
In such case drug solubility in the formulation may be compromised by small
changes in pH (upon administration or prolonged storage)

Enhance Product stability
If the chemical stability of the drug is pH dependent

pH adjusters can be acids (e.g. Citric acid), bases (e.g. Sodium hydroxide) or buffers.

Examples of buffer salts used in pharmaceutical solutions

Acetates (acetic acid and sodium acetate)
Phosphates (sodium phosphate and disodium phosphate)
Citrates (citric acid and sodium citrate)

Buffers resist significant changes in pH, ensuring a more stable pH environment
compared to standalone acids or bases (Buffering capacity)

2. Anti-oxidants 16/77

Anti-oxidants enhance the stability of drugs that are susceptible to chemical degradation by
oxidation.

Water-soluble anti-oxidants such as sodium metabisulphite, sodium sulphite, sodium
bisulfate, ascorbic acid, are used to stabilize aqueous solutions.

Fat-soluble anti-oxidants such as butylated hydroxytoluene (BHT), butylated hydroxyanisole
(BHA) and propyl gallate, are used to stabilize oily solutions.

Antioxidants are usually added with chelating agents (ethylenediamine tetraacetic acid
(EDTA) and citric acid) that act to form complexes with metal ions that are normally involved
in the oxidative degradation of drugs

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