Pharmaceutics Flashcards

Which property of a drug substance is MOST critical for absorption via passive transcellular diffusion across biological membranes?

Answer: Lipophilicity

Lipophilicity allows drugs to partition into and diffuse across the lipid bilayer via passive transcellular diffusion.

According to USP, a 'dilute solution' for oral use contains what maximum concentration of alcohol?

Answer: 10%

USP defines dilute oral solutions as containing not more than 10% alcohol to limit systemic alcohol exposure.

Which type of flow behavior is exhibited by a material whose viscosity decreases under shear stress and does not recover immediately when shear is removed?

Answer: Thixotropic

Thixotropic materials show time-dependent shear thinning; viscosity decreases under shear and recovers slowly after shear removal, forming a hysteresis loop.

A suppository base that melts at body temperature and is water-soluble is BEST described as:

Answer: Polyethylene glycol (PEG)

PEG suppository bases are water-soluble and dissolve in rectal fluids rather than melting, making them suitable for drugs incompatible with fatty bases.

In lyophilization (freeze-drying), primary drying removes water by:

Answer: Sublimation of ice under reduced pressure

Primary drying in lyophilization removes frozen water by sublimation under vacuum, bypassing the liquid phase.

Which parameter is used to quantify the drug content uniformity of solid dosage forms according to USP?

Answer: Relative standard deviation (RSD)

USP content uniformity testing uses the Acceptance Value (AV) based on the mean and RSD of individual unit drug content.

Hydrophilic-lipophilic balance (HLB) values between 8 and 18 are MOST suitable for:

Answer: O/W emulsifiers

HLB values of 8–18 indicate predominantly hydrophilic surfactants, which are effective stabilizers for oil-in-water emulsions.