When ointments contain water, which of the following is true about preservatives?

• A. They cannot be used regardless of water content
• B. Parabens and phenols are the only acceptable preservatives
• C. They must be used at high concentrations
• D. True when water is present and appropriate antimicrobials are used

Answer: (D)

Water in an ointment creates a chance for microbes to grow, so a preservative system is usually needed to keep the product safe during manufacturing and storage. When there is an aqueous phase, using an appropriate antimicrobial helps prevent contamination, but it must be chosen to suit the formulation and used at the right level. This is why the statement that applies is: preservatives are needed if water is present and the antimicrobials chosen are suitable for that specific formulation. The other options are off because preservatives aren’t universally forbidden with water, there are many acceptable preservatives beyond just parabens and phenols, and preservatives aren’t required at high concentrations—they are used at the minimum effective, regulatory-approved levels.