Pharmaceutical Chemistry and Pharmacology Flashcards

Which drug is used for the reversal of neuromuscular blockade from non-depolarizing agents like vecuronium?

Answer: Neostigmine (with atropine) or sugammadex

Neostigmine (acetylcholinesterase inhibitor) reverses non-depolarizing neuromuscular blockade by increasing acetylcholine at the NMJ to compete with the blocker. Atropine prevents muscarinic side effects (bradycardia, hypersalivation). Sugammadex (cyclodextrin) directly encapsulates rocuronium/vecuronium for rapid reversal.

A pharmacist identifies that a patient is prescribed both fluoxetine (SSRI) and tramadol. What is the clinical concern?

Answer: Serotonin syndrome and reduced tramadol activation (fluoxetine inhibits CYP2D6)

Fluoxetine inhibits CYP2D6, which both activates tramadol to its active mu-opioid metabolite (O-desmethyltramadol) AND the combination increases serotonergic activity (tramadol + SSRI), dramatically raising serotonin syndrome risk. Two separate hazardous mechanisms exist with this combination.

The therapeutic index (TI) of a drug is calculated as:

Answer: TD50 / ED50 (or LD50 / ED50) — ratio of toxic dose to effective dose

Therapeutic index = TD50 (dose toxic in 50% of population) / ED50 (dose effective in 50% of population). A narrow TI (e.g., digoxin, lithium, warfarin, aminoglycosides) means the toxic dose is close to the therapeutic dose, requiring careful monitoring. Wide TI drugs have a large safety margin.

Which antiviral mechanism does oseltamivir (Tamiflu) use to treat influenza?

Answer: Neuraminidase inhibitor — prevents viral release from host cells

Oseltamivir inhibits influenza neuraminidase (sialidase), the enzyme that cleaves sialic acid residues allowing newly formed virions to be released from the host cell. Without neuraminidase, virions aggregate on the cell surface and cannot infect new cells. Effective against influenza A and B.

A pharmacist is reviewing drug metabolism. What is the purpose of Phase II (conjugation) reactions?

Answer: To add a polar group (glucuronic acid, sulfate, glycine, acetate) to increase water solubility and facilitate renal/biliary excretion

Phase II reactions conjugate the drug (or Phase I metabolite) with polar endogenous molecules (glucuronic acid, sulfate, glutathione, amino acids, acetyl group). This dramatically increases water solubility, reducing lipophilicity and enabling renal or biliary excretion. Phase II usually terminates pharmacological activity.

What is the clinical significance of CYP3A4 inhibition by grapefruit juice?

Answer: Grapefruit irreversibly inhibits intestinal CYP3A4, increasing oral bioavailability and plasma levels of many drugs

Grapefruit juice contains furanocoumarins that irreversibly inhibit intestinal (not hepatic) CYP3A4 and P-glycoprotein. This increases the oral bioavailability of drugs with high first-pass metabolism (e.g., statins, calcium channel blockers, cyclosporine). A single glass can inhibit intestinal CYP3A4 for 24–72 hours.