GPhC Pharmaceutical Sciences & Calculations 3

Question 1

What is the osmolarity of normal saline (0.9% NaCl) approximately?

Accepted Answer

308 mOsm/L

Answer

0.9% NaCl dissociates into Na+ and Cl−, each at 154 mmol/L, giving approximately 308 mOsm/L, which is isotonic with blood.

Question 2

Which type of interaction occurs when two drugs compete for the same plasma protein binding site?

Accepted Answer

Pharmacokinetic displacement interaction

Answer

Protein binding displacement is a pharmacokinetic interaction where one drug displaces another from albumin or other proteins, increasing free drug concentration.

Question 3

A suppository base that melts at body temperature is described as:

Accepted Answer

Theobroma oil base

Answer

Theobroma oil (cocoa butter) melts at approximately 34–35°C, close to body temperature, making it suitable for rectal suppositories.

Question 4

What does 'bioavailability' refer to?

Accepted Answer

The fraction of administered drug that reaches systemic circulation

Answer

Bioavailability (F) is the proportion of an administered dose that reaches the systemic circulation unchanged. IV administration gives 100% bioavailability.

Question 5

Which polymorphic form of a drug is generally more soluble?

Accepted Answer

Amorphous form

Answer

Amorphous solids lack a regular crystal lattice, making them more soluble and often more bioavailable than crystalline forms of the same drug.

GPhC Registration Practice Test

GPhC Registration Practice Test

GPhC Pharmaceutical Sciences & Calculations 3