Pharmaceutical Sciences Flashcards

What is bioavailability and why is it important in pharmacy practice?

Answer: The fraction of administered drug that reaches systemic circulation in unchanged form, affecting therapeutic efficacy

Bioavailability (F) measures the fraction of active drug reaching systemic circulation. IV administration has 100% bioavailability. Oral bioavailability is reduced by first-pass metabolism, absorption barriers, and drug stability. It determines whether oral doses achieve therapeutic levels.

What is the difference between a generic drug and a branded drug?

Answer: Generic drugs contain the same active ingredient, dose, and dosage form but may differ in inactive ingredients, and must demonstrate bioequivalence

Generic drugs contain the same active pharmaceutical ingredient (API) in the same dose, dosage form, and route as the brand. SFDA requires bioequivalence studies proving 80-125% confidence interval for AUC and Cmax compared to the reference product.

What is the purpose of stability testing in pharmaceutical manufacturing?

Answer: To determine how a drug product maintains its quality, safety, and efficacy over time under specified storage conditions

Stability testing evaluates how temperature, humidity, and light affect a drug's physical, chemical, microbiological, and therapeutic properties over time. Results determine shelf life, storage conditions, and expiry dates — essential for Saudi Arabia's hot climate.

What is the first-pass effect and how does it influence oral drug therapy?

Answer: The initial metabolism of orally administered drugs by the liver before reaching systemic circulation, reducing bioavailability

The first-pass effect occurs when orally administered drugs are absorbed from the GI tract into the portal circulation and metabolized by the liver before reaching systemic circulation. Drugs with high first-pass metabolism (nitroglycerin, morphine) require higher oral doses or alternative routes (sublingual, IV).

What is the therapeutic index and why is it clinically significant?

Answer: The ratio of toxic dose to therapeutic dose (TD50/ED50), indicating the drug's safety margin

Therapeutic index = TD50/ED50. A narrow therapeutic index (NTI) means the toxic dose is close to the therapeutic dose (e.g., warfarin, digoxin, lithium, phenytoin). These drugs require careful dosing, monitoring, and pharmacist vigilance for interactions.

How does Saudi Arabia's climate affect drug storage and stability?

Answer: Extreme heat (40-50°C) can accelerate drug degradation, requiring strict cold chain management and proper storage conditions

Saudi Arabia's extreme heat accelerates chemical degradation, affects drug stability, and requires robust cold chain logistics. Temperature-sensitive medications (insulin, vaccines, biologics) need refrigeration. Even room-temperature drugs may degrade faster, requiring SFDA-compliant storage monitoring.