Pharmaceutical Sciences Flashcards
6 cards from real PSI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Pharmaceutical Sciences flashcards as text
Which cytochrome P450 enzyme is responsible for the metabolism of the largest number of drugs?
Answer: CYP3A4
CYP3A4 is the most abundant hepatic CYP enzyme and metabolises approximately 50% of all drugs. It is subject to many important drug interactions.
Renal clearance of a drug is increased when the drug is:
Answer: Ionised at urinary pH
Ionised drugs cannot readily be reabsorbed through tubular epithelium, so they remain in urine and are excreted. Manipulating urinary pH to increase ionisation is used in poisoning management.
Which dosage form is designed to release drug in the small intestine rather than the stomach?
Answer: Enteric-coated tablet
Enteric coatings (e.g., HPMC phthalate) resist acidic gastric pH but dissolve at the higher pH of the small intestine, protecting acid-labile drugs or preventing gastric irritation.
Steady-state plasma concentration is reached after approximately how many half-lives of continuous dosing?
Answer: 5 half-lives
With repeated dosing, drug accumulates until input equals output. Steady state is effectively reached after 4–5 half-lives, when ~97% of the final plateau concentration is achieved.
Which type of isomerism involves non-superimposable mirror image molecules?
Answer: Enantiomerism
Enantiomers are mirror images that cannot be superimposed. They have identical physical properties but can differ in pharmacological activity, toxicity and metabolism.
An isotonic solution has the same osmolarity as:
Answer: Blood plasma (~285–310 mOsm/kg)
Isotonic solutions match the osmolarity of blood plasma (~285–310 mOsm/kg), preventing osmotic shift across cell membranes. Both normal saline (0.9%) and 5% glucose are isotonic examples.