Pharmaceutical Sciences & Calculations Flashcards

Which concentration unit is used for very dilute solutions in pharmacy?

Answer: Parts per million (ppm)

Parts per million (ppm) is used for very dilute solutions, equivalent to 1 mg per litre (1 mg/L) or 1 µg/mL for aqueous solutions.

A cream is an example of which type of pharmaceutical system?

Answer: Emulsion

Creams are semi-solid emulsions (either O/W or W/O) intended for external application, consisting of two immiscible phases stabilised by an emulsifying agent.

What is the role of a surfactant in pharmaceutical formulations?

Answer: Reduces surface tension to improve wetting and emulsification

Surfactants (surface-active agents) reduce surface tension at interfaces, aiding wetting, emulsification, solubilisation, and dispersion of poorly soluble drugs.

Zeta potential is used to assess:

Answer: Physical stability of colloidal dispersions

Zeta potential measures the electrostatic charge on colloidal particles. A high absolute zeta potential (>±30 mV) indicates good electrostatic repulsion and physical stability.

Which sterilisation method is preferred for heat-labile products?

Answer: Filtration through 0.22 µm membrane

Membrane filtration (0.22 µm) physically removes microorganisms without heat, making it suitable for thermolabile solutions such as proteins or certain injectables.

What is the purpose of a disintegrant in a tablet formulation?

Answer: To promote tablet breakup in GI fluids

Disintegrants (e.g., sodium starch glycolate, croscarmellose sodium) absorb water and swell or create channels that cause tablets to break apart in GI fluid.