Pharmaceutical Chemistry and Pharmacology Flashcards

Digoxin's positive inotropic effect is mediated by which mechanism?

Answer: Inhibition of Na+/K+-ATPase pump, increasing intracellular Na+, which increases intracellular Ca2+ via Na+/Ca2+ exchange

Digoxin inhibits the Na+/K+-ATPase pump. This raises intracellular Na+, which reduces Na+/Ca2+ exchanger (NCX) activity, increasing intracellular Ca2+, and thus increasing myocardial contractility. Digoxin also increases vagal tone, slowing AV conduction (used in AF rate control).

Which drug is used to reverse the effects of benzodiazepine overdose?

Answer: Flumazenil — competitive GABA-A receptor antagonist

Flumazenil is a competitive benzodiazepine antagonist at the GABA-A receptor. It rapidly reverses benzodiazepine-induced sedation, respiratory depression, and coma. Its short half-life (1 hour) means re-sedation can occur, requiring repeat dosing or monitoring.

A pharmacist is counseling a patient about tamoxifen for breast cancer prevention. What is the mechanism of action of tamoxifen?

Answer: Selective estrogen receptor modulator (SERM) — antagonist in breast tissue, partial agonist in uterus and bone

Tamoxifen is a SERM with tissue-selective estrogen receptor effects. In breast tissue, it antagonizes estrogen, inhibiting estrogen receptor-positive (ER+) breast cancer growth. In the uterus, it acts as a partial agonist, increasing risk of endometrial cancer. In bone, it acts as an agonist, protecting bone density.

Which receptor type mediates the therapeutic bronchodilation effect of salbutamol (albuterol)?

Answer: Beta-2 adrenergic receptor in bronchial smooth muscle

Salbutamol is a selective beta-2 adrenergic agonist. Activation of beta-2 receptors in bronchial smooth muscle activates adenylyl cyclase → increases cAMP → activates PKA → phosphorylates myosin light chain kinase → causes bronchial smooth muscle relaxation (bronchodilation).

A pharmacist is reviewing the structure-activity relationships (SAR) of opioids. Which structural feature is essential for opioid receptor binding?

Answer: A phenolic hydroxyl group at position 3 and a tertiary nitrogen

The classic morphine-like opioid pharmacophore requires: a phenolic hydroxyl at C-3 (essential for mu-receptor affinity), a hydroxyl at C-6, and a basic nitrogen. Methylation of the C-3 hydroxyl (as in codeine) reduces potency. This SAR guides opioid drug design.

Which phenomenon explains why repeated morphine administration leads to progressively higher doses being needed for pain relief?

Answer: Pharmacodynamic tolerance — receptor downregulation and desensitization

Chronic opioid use leads to receptor desensitization (phosphorylation and uncoupling from G proteins), downregulation (reduced receptor number), and tolerance at second messenger levels. Both pharmacodynamic and pharmacokinetic (induction of CYP3A4) tolerance contribute to reduced opioid effect.